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FWHA Highway & Rail Transit Tunnel Maintenance & Rehabilitation Manual 4TH ED | Mechanical Fan | Tunnel
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Tunnel Maintenance and Rehabilitation Manual
List of Tables List of Figures Executive Summary CHAPTER 1: INTRODUCTION............................................................................................ 1-1 CHAPTER 2: TUNNEL CONSTRUCTION AND SYSTEMS ............................................ 2-1 A. Tunnel Types .............................................................................................................. 2-1 1. Shapes ............................................................................................................. 2-1 2. Liner Types...................................................................................................... 2-7 3. Invert Types ..................................................................................................... 2-8 4. Construction Methods................................................................................... 2-11 5. Tunnel Finishes ............................................................................................. 2-12 B. Ventilation Systems .................................................................................................. 2-15 1. Types ............................................................................................................. 2-15 2. Equipment ..................................................................................................... 2-19 C. Lighting Systems...................................................................................................... 2-21 1. Types ............................................................................................................. 2-21 D. Other Systems/Appurtenances ................................................................................. 2-22 1. Track ............................................................................................................. 2-22 2. Power (Third Rail/Catenary) ........................................................................ 2-23 3. Signal/Communication Systems .................................................................... 2-25 CHAPTER 3: PREVENTIVE MAINTENANCE.................................................................. 3-1 A. Preventive Maintenance of the Tunnel Structure................................................. 3-1 1. Tunnel Washing ............................................................................................... 3-1 2. Drain Flushing................................................................................................ 3-1 3. Ice/Snow Removal........................................................................................... 3-2 4. Tile Removal.................................................................................................... 3-2 Preventive Maintenance of Mechanical Systems ................................................ 3-2 Preventive Maintenance of Electrical Elements .................................................. 3-8 Preventive Maintenance of Track Systems ........................................................ 3-15 1. Track and Supporting Structure.................................................................... 3-15 2. Power (Third Rail/Catenary) ........................................................................ 3-17 3. Signal/Communication Systems .................................................................... 3-18
.............................................. Water Infiltration .......... Vent Structures and Emergency Egress Shafts .......................... 3-18 2.......................................... Steel.............. 4-29 1..... 4-23 C...................................................................... Shotcrete......................... Safety Walks........................... 4-35 7......Tunnel Maintenance and Rehabilitation Manual E............. 4-35 6. Pre-cast Concrete........................................................... Corrosion Protection Systems........................................................................................... Consequences of Water Infiltration....................................................... 4-3 B.......................................... 4-1 2........................................... Preventive Maintenance of Miscellaneous Appurtenances.................. Exposed Rock ................................................................. A-1 Glossary ........................................................................................................... G-1 References ......... 4-32 5....... 4-1 A................. 4-20 2...................... 3-20 3....................................................... Concrete Repairs.................................... R-1 ii Federal Transit Administration ............................................................................................................................................................................................................................................................................................................................................................................................................................... 4-19 1.................... 3-21 CHAPTER 4: REHABILITATION OF STRUCTURAL ELEMENTS ..................... 4-1 1.................................................................................................................. Rails........................... Spall .................................... Remediation Methods.......................... Masonry ........ 4-30 4................................. 4-2 3. Crack................... Problem................................................... 3-18 1............................................. and Exit Stair/Ladder Structures ... 4-30 3.................................. Liner Repairs............................................................................... Cast Iron .. Cast-in-Place (CIP) Concrete................................................................................. 4-36 Appendix A: Life Cycle Cost Methodology .................................. 4-29 2...................................................................................
.................................1 Table 3..........1 – Construction Methods.................................2 Table 4.. 2-11 – Preventive Maintenance of Mechanical Systems .. 4-31 Federal Highway Administration iii ....................................1 Table 3...............................................................Tunnel Maintenance and Rehabilitation Manual LIST OF TABLES Table 2....... 3-4 – Preventive Maintenance of Electrical Systems.................................................. 3-9 – Weldability of Steel.
................................................................................................................... 2-10 Figure 2......................................... 4-3 iv Federal Transit Administration ............................................................... 2-3 Figure 2.17 – Axial Fans ......................................9 – Oval Rail Transit Tunnel Shape ................. 2-24 Figure 4..............1 – Circular Highway Tunnel Shape................... 2-20 Figure 2...............Tunnel Maintenance and Rehabilitation Manual LIST OF FIGURES Figure 2................11 – Single Box Tunnel Invert Type ......... 2-2 Figure 2......... 2-2 Figure 2............................................................................. 2-10 Figure 2......8 – Horseshoe Rail Transit Tunnel Shape .....................19 – Typical Third Rail Power System ......................... 2-5 Figure 2......................14 – Longitudinal Ventilation ...................................................................................................................................10 – Circular Tunnel Invert Type...........5 – Circular Rail Transit Tunnel Shape...........................13 – Natural Ventilation .............. 2-4 Figure 2...............4 – Oval/Egg Highway Tunnel Shape................................................................... 2-15 Figure 2......................... 2-17 Figure 2.................................... 2-6 Figure 2...........3 – Horseshoe Highway Tunnel Shape ...2 – Double Box Highway Tunnel Shape............20 – Typical Third Rail Insulated Anchor Arm..................15 – Semi-Transverse Ventilation ..............18 – Centrifugal Fan .............12 – Horseshoe Tunnel Invert Type ............................... 2-5 Figure 2.............. 2-16 Figure 2..................6 – Double Box Rail Transit Tunnel Shape .... 2-6 Figure 2............ 2-3 Figure 2.................................. 2-24 Figure 2...............................................................1 – Ice formation at location of water infiltration in plenum area above the roadway slab............................................................ 2-9 Figure 2................................... 2-18 Figure 2............7 – Single Box Rail Transit Tunnel Shape .................................... 2-19 Figure 2.......................................16 – Full-Transverse Ventilation.............................................................................................................................
...........................4-22 Figure 4..........4-10 Figure 4...........................4-28 Figure 4....11 – Horizontal surface crack repair detail ...........14 – Shallow spall repair detail (shallow spall with reinforcement steel exposed)..............................................................................................4-15 Figure 4...4-37 Federal Highway Administration v .....................................2 – Temporary drainage systems comprised of neoprene rubber troughs and 25 mm (1 in) aluminum channels.........4-24 Figure 4......4-7 Figure 4....4-27 Figure 4....................................................................9 – Method of repairing a leaking joint ........................................................13 – Shallow spall repair detail (shallow spall with no reinforcement steel exposed)..........4-18 Figure 4......................7 – Repair of a concrete joint or crack by inclusion of a neoprene strip ....................4-14 Figure 4..........................20 – Rock bolt types ..10 – Laser controlled cutter for removing portions of existing tunnel liner.............6 – Leaking crack repair detail..4-4 Figure 4...17 – Metal Stitching Detail .............4-33 Figure 4..........19 – Metal Stitching Completed ............4-34 Figure 4........................................8 – Treatment of cracks by membrane covering.............4-33 Figure 4..............16 – Deep spall with exposed inadequate reinforcement steel ....18 – Metal Stitching Procedure......................4-25 Figure 4....4-6 Figure 4........................................3 – Temporary drainage system comprised of 50 mm (2 in) plastic pipe........................................................................................................................15 – Deep spall with exposed adequate reinforcement steel .................................................5 – Section of membrane waterproofing system...........4-16 Figure 4.........................................................................................................4 – Insulated panels used as a waterproofing lining to keep infiltrated water from freezing........4-21 Figure 4................12 – Vertical/over head crack repair detail .........Tunnel Maintenance and Rehabilitation Manual Figure 4...........................................4-5 Figure 4...................................
Tunnel Maintenance and Rehabilitation Manual vi Federal Transit Administration .
Gannett Fleming. It is commonly understood that numerous tunnels in the United States are more than 50 years old and are beginning to show signs of considerable deterioration. Introduction This chapter presents a brief history of the project development and outlines the scope and contents of the Maintenance and Rehabilitation Manual. the various construction methods utilized to construct a tunnel. and the multiple different finishes that can be applied. the two main invert types. a few elements are specific to either highway or rail transits tunnels. and signal/communications systems. In addition. to develop the first ever Tunnel Management System to benefit both highway and rail transit tunnel owners throughout the United States and Puerto Rico. such as: track systems.Tunnel Maintenance and Rehabilitation Manual EXECUTIVE SUMMARY In March of 2001. the Federal Transit Administration (FTA) engaged Gannett Fleming. this chapter was developed to define those major systems and describe how they relate to both highway and rail transit tunnels.. these federal agencies. Inc. and other systems/appurtenances. power systems (third rail/ catenary). ventilation systems. Although several components are similar in both types of tunnels. lighting systems. Specifically. This chapter is broken down into four sub-chapters that include: tunnel types. and a computerized database wherein all inventory. The other systems/appurtenances section is used to explain tunnel systems that are present in rail transit tunnels. set a common goal to provide uniformity and consistency in assessing the physical condition of the various tunnel components. The tunnel types section covers the different tunnel shapes in existence. Tunnel Construction and Systems To develop uniformity concerning certain tunnel components and systems. Inc. 2003. The ventilation and lighting system sections are self explanatory in that they cover the basic system types and configurations. To accomplish these ONE DOT goals.. Preventive Maintenance This chapter provides specific recommendations for performing preventive maintenance Federal Highway Administration vii . liner types that have been used. It provides specific information for the maintenance and rehabilitation of both highway and rail transit tunnels. acting as ONE DOT. it is desired that good maintenance and rehabilitation practices be presented that would aid tunnel owners in the repair of identified deficiencies. a Maintenance and Rehabilitation Manual. This manual is an update to the version issued in May. was tasked to produce an Inspection Manual. especially due to water infiltration. and are defined accordingly. mainly in highway tunnels. and repair data could be collected and stored for historical purposes. inspection. The following paragraphs explain the specific subjects covered along with procedural recommendations that are contained in this manual.
power (third rail/catenary). mechanical systems. Rehabilitation of Structural Elements The last chapter of this manual offers general procedural recommendations for making structural repairs to various types of tunnel liner materials. The last section for miscellaneous appurtenances covers the following three categories: 1) corrosion protection systems. 2) safety walks. pre-cast concrete. The last section deals with each of the following liner types: cast-inplace concrete. Life-Cycle Cost Methodology Appendix A of this manual includes a general discussion of life-cycle-cost methodology. stop. The procedures for the mechanical and electrical systems/ elements are given in tabular format and include a suggested frequency for each of the tasks listed. cast iron. track systems. steel. Following that section is a detailed section that addresses the various structural repairs that can be made to concrete. or adequately divert water infiltration. and 3) vent structures and emergency egress shafts. This process could be used when determining which method of repair is most cost effective over the long term. and exit stair/ ladder structures.Tunnel Maintenance and Rehabilitation Manual to the tunnel structure. such as repairing cracks and spalls. it could be used to determine if it is more beneficial to purchase a new piece of equipment or to continue maintaining the existing piece. rails. shotcrete. and signal/communication systems. A large section is devoted to covering repairs necessary to slow. masonry. electrical elements. drain flushing. viii Federal Transit Administration . Also. ice/snow removal and tile removal. Track systems are divided into track and supporting structure. and exposed rock. The tunnel structure recommendations deal with tunnel washing. and miscellaneous appurtenances.
height.Tunnel Maintenance and Rehabilitation Manual CHAPTER 1: INTRODUCTION Background In 1999. for concrete tunnels more than 50 years in age it is highly likely that the concrete was not air-entrained and. inventory information collected to date. Phase 1 of this project involved the development of an inventory database of the nation’s highway and rail transit tunnels that included such information as location of the tunnel. and to be placed in the public domain. suggests that there are approximately 346 km (215 miles) of rail transit tunnels greater than 50 years old. Since numerous tunnels have been subjected to these conditions for many years. Similarly. To avoid future potential major operation problems due to deferred maintenance. Groundwater infiltration through joints and cracks in tunnels is the number one cause of deterioration of the various tunnel elements. tunnels subjected to temperature gradients may have suffered damage over the years due to freeze-thaw actions. lining/support types. it is vitally important that tunnel owners commence regular preventive maintenance and repair procedures for correcting deficiencies such that each tunnel can continue to function as originally designed. the two agencies decided to jointly sponsor the development of a Tunnel Management System for both highway and rail transit tunnel owners. This data is sufficient to indicate that these older highway and rail transit tunnels contain elements that are deteriorating and in need of repair. the construction method employed. shape. tunnel name. a computerized database system was also developed to assist with the storage and management of tunnel condition data and for prioritizing repairs. construction ground conditions. Along with the Inspection Manual and this companion Maintenance and Rehabilitation Manual. The data received from highway tunnel owners responding to the questionnaire revealed that more than 32 percent of reported highway tunnels are between 50-100 years old. width. It is the intent of the FHWA and FTA that these products be furnished to each highway and rail transit tunnel owner across the nation. plus data known to exist for certain agencies that had trouble segmenting all of their tunnels according to the questionnaire. and types of mechanical/electrical systems. the Federal Transit Administration (FTA) is responsible for providing guidance on tunnel management to rail transit owners. the Federal Highway Administration (FHWA) created an office to focus on management of highway assets. FHWA and FTA sponsored this project to develop inspection procedures and guidance for maintenance practices within highway and rail transit tunnels and to assist tunnel owners in maintaining their tunnels. with 4 percent greater than 100 years old. In addition. age. Although it is more difficult to categorize rail transit tunnels by percent. length. including highway tunnels. Federal Highway Administration 1-1 . therefore. Part of this office is responsible for providing guidance and technical assistance to state and local highway agencies on structure management issues. Because of this common interest in tunnel management procedures.
the description of tunnel components such as tunnel configuration. 1-2 Federal Transit Administration . the number one cause of deterioration. liner types. traction power. Suggested repairs to the tunnel structure for various deficiencies are provided. It is not the intent to replace current practices unless the tunnel owner decides to do so as a benefit to his/her program. signals and communications) are each provided in separate sections to assist tunnel owners in educating their inspectors as to the particular system existing within the tunnel. invert types. ventilation systems. The incorporation of the guidelines presented herein and the use of a documented maintenance and inspection program (via the software provided) will help tunnel owners to program needed maintenance and rehabilitation costs.Tunnel Maintenance and Rehabilitation Manual Scope The purpose of this manual is to provide highway and rail transit tunnel owners with guidelines and practices for preventive maintenance of both the tunnel structure and the mechanical/electrical/track systems within. Contents To promote consistency of definition of particular elements. For example. These repairs include guidelines for controlling water infiltration into the tunnel. lighting systems. It is important to note that the guidelines and practices included are intended to supplement existing programs and procedures already in place. this manual contains several chapters that explain the various types of elements that exist within the tunnel. tunnel finishes and other systems/appurtenances (track.
1. As a general guideline a minimum length of 100 meters (~300 feet) was used in defining a tunnel for inventory purposes. The purpose of this section is to look at the types that are most commonly used in tunnel construction to help the inspector properly classify any given tunnel.Tunnel Maintenance and Rehabilitation Manual CHAPTER 2: TUNNEL CONSTRUCTION AND SYSTEMS A. Federal Highway Administration 2-1 . construction method.4. Another possible highway tunnel shape that is not shown is a single box with bi-directional traffic. The different shapes typically relate to the method of construction and the ground conditions in which they were constructed. and tunnel finishes. liner type.1 to 2. there are four main shapes of highway tunnels – circular. rectangular. the outside shape of the tunnel defines its type. however other reasons for using the tunnel classification may exist such as the presence of lighting or a ventilation system. horseshoe. due to horizontal roadways and ceiling slabs. These tunnel types are described by their shape. and oval/egg. Shapes a) Highway Tunnels As shown in Figures 2. It should be noted that other types may exist currently or be constructed in the future as new technologies become available. TUNNEL TYPES This section describes the various types of highway and rail transit tunnels. Some tunnels may be constructed using combinations of these types due to different soil conditions along the length of the tunnel. Although many tunnels will appear rectangular from inside. which could override the length limitation. invert type. This length is primarily to exclude long underpasses.
Tunnel Maintenance and Rehabilitation Manual Figure 2. 2-2 Federal Transit Administration . Invert may be solid concrete over liner or a structural slab. Also shown is an alternative ceiling slab. Figure 2. the center wall may be solid or composed of consecutive columns.2 – Double box tunnel with two traffic lanes and one safety walk in each box. Depending on location and loading conditions.1 – Circular tunnel with two traffic lanes and one safety walk.
Federal Highway Administration 2-3 . Invert may be a slab on grade or a structural slab.Tunnel Maintenance and Rehabilitation Manual Figure 2.3 – Horseshoe tunnel with two traffic lanes and one safety walk. Also shown is an alternative ceiling slab.4 – Oval/egg tunnel with three traffic lanes and two safety walks. Figure 2. Also shown is an alternative ceiling slab.
Invert slab is placed on top of liner. However.Tunnel Maintenance and Rehabilitation Manual b) Rail Transit Tunnels Figures 2.5 – Circular tunnel with a single track and one safety walk. the change in shape may also occur between stations due to variations in ground conditions. the shape typically relates to the method/ground conditions in which they were constructed. 2-4 Federal Transit Administration . The shape of rail transit tunnels often varies along a given rail line. As with highway tunnels. These shapes typically change at the transition between the station structure and the typical tunnel cross-section.9 show the typical shapes for rail transit tunnels.5 to 2. Figure 2.
Tunnel is usually constructed beside another single box tunnel for opposite direction travel.6 – Double box tunnel with a single track and one safety walk in each box. Federal Highway Administration 2-5 . Depending on location and loading conditions. center wall may be solid or composed of consecutive columns.7 – Single box tunnel with a single track and one safety walk. Figure 2.Tunnel Maintenance and Rehabilitation Manual Figure 2.
Tunnel Maintenance and Rehabilitation Manual Figure 2.9 – Oval tunnel with a single track and one safety walk. 2-6 Federal Transit Administration . Figure 2.8 – Horseshoe tunnel with a single track and one safety walk. This shape typically exists in rock conditions and may be unlined within stable rock formations.
Linings of other types may exist at portals or at limited zones of weak rock. or tensioned steel bolts. shotcrete. some of which have been converted into highway tunnels for local access. b) Rock Reinforcement Systems Rock reinforcement systems are used to add additional stability to rock tunnels in which structural defects exist in the rock. c) Shotcrete Shotcrete is appealing as a lining type due to its ease of application and short “stand-up” time. To prevent small fragments of rock from spalling off the lining. a) Unlined Rock As the name suggests. Liner Types Tunnel liner types can be described using the following classifications: •Unlined Rock • Rock Reinforcement Systems • Shotcrete • Ribbed Systems • Segmental Linings • Placed Concrete • Slurry Walls. it is difficult to determine the lining type without having knowledge of the construction method. This type of liner was common in older railroad tunnels in the western mountains. synthetic fibers as reinforcement. However. The inside surface can be finished smooth as with regular concrete. When this is the case. The intent of these systems is to unify the rock pieces to produce a composite resistance to the outside forces. d) Ribbed Systems Ribbed systems are typically a two-pass system for lining a drill-andFederal Highway Administration 2-7 . Reinforcement systems include the use of metal straps and mine ties with short bolts. or a thin concrete lining may be used in conjunction with the above systems. an unlined rock tunnel is one in which no lining exists for the majority of the tunnel length. therefore. shotcrete can be used as a final lining. it is typically placed in layers and can have metal or randomly oriented.Tunnel Maintenance and Rehabilitation Manual 2. Shotcrete is primarily used as a temporary application prior to a final liner being installed or as a local solution to instabilities in a rock tunnel. wire mesh. untensioned steel dowels.
The prefabricated lining segments are erected within the cylindrical tail shield of the TBM. or cast iron and are usually bolted together to compress gaskets for preventing water penetration. They can be designed as a non-structural finish element or as the main structural support for the tunnel. Then a reinforcing cage is lowered into the slurry or soldier piles are driven at a predetermined interval and finally tremie concrete is placed into the excavation. which stabilizes the sidewalls. 2-8 Federal Transit Administration . This trench is continually kept full with a drilling fluid during excavation. e) Segmental Linings Segmental linings are primarily used in conjunction with a tunnel boring machine (TBM) in soft ground conditions. or precast concrete ribs usually with blocking between them. They can be reinforced or unreinforced. 3. f) Placed Concrete Placed concrete linings are usually the final linings that are installed over any of the previous initial stabilization methods. steel. Another application of this system is to form the ribs using prefabricated reinforcing bar cages embedded in multiple layers of shotcrete.Tunnel Maintenance and Rehabilitation Manual blast rock tunnel. which are separated with watertight joints. There are two main methods for supporting the roadway or track bed. but typically they consist of excavating a trench that matches the proposed wall profile. which displaces the drilling fluid. This procedure is repeated in specified panel lengths. One other soft ground application is to place “barrel stave” timber lagging between the ribs. g) Slurry Walls Slurry wall construction types vary. They can be used as a thin cover layer over the primary liner to provide a finished surface within the tunnel or to sandwich a waterproofing membrane. This method is also employed in many highway tunnels over land where ventilation is supplied from above the roadway level. one is by placing the roadway or track bed directly on grade at the bottom of the tunnel structure. The second pass typically consists of poured concrete that is placed inside of the ribs. The first method is used in most rail transit tunnels because their ventilation systems rarely use supply ductwork under the slab. concrete. This provides structural stability to the tunnel. Invert Types The invert of a tunnel is the slab on which the roadway or track bed is supported. and the other is to span the roadway between sidewalls to provide space under the roadway for ventilation and utilities. These prefabricated segments can be made of steel. The first pass consists of timber.
Tunnel Maintenance and Rehabilitation Manual The second method is commonly found in circular highway tunnels that must provide a horizontal roadway surface that is wide enough for at least two lanes of trafficand therefore the roadway slab is suspended off the tunnel bottom a particular distance.10 to 2. that span transversely to the tunnel length.10 – Circular tunnel with a structural slab that provides space for an air plenum below. Figure 2. Newer tunnels. The void is then used for a ventilation plenum and other utilities. similar to the second Hampton Roads Tunnel in Virginia. provide structural reinforced concrete slabs that span the required distance between supports. Examples of structural slabs in common tunnel shapes are shown in Figures 2. The roadway slab in many of the older highway tunnels in New York City is supported by placing structural steel beams. Federal Highway Administration 2-9 .500 mm (60 in) on centers. encased in concrete.12. and are spaced between 750 mm (30 in) and 1. It is necessary to determine the type of roadway slab used in a given tunnel because a more extensive inspection is required for a structural slab than for a slab-on-grade.
Figure 2.11 – Single box tunnel with a structural slab that provides space for an air plenum below.Tunnel Maintenance and Rehabilitation Manual Figure 2. 2-10 Federal Transit Administration .12 – Horseshoe tunnel with a structural slab that provides space for an air plenum below.
Tunnel Maintenance and Rehabilitation Manual 4. the shape of the tunnel is largely dependent on the method used to construct the tunnel. tie back anchors or slurry wall systems to construct the walls of a cut and cover tunnel. Table 2. d) Drill and Blast An alternative to using a TBM in rock situations would be to manually drill and blast the rock and remove it using conventional conveyor techniques. The material inside the shield is removed and a lining system is constructed before the shield is advanced further. This method was commonly used for older tunnels and is still used when it is determined cost effective or in difficult ground conditions.1 lists the seven main methods used for tunnel construction with the shape that typically results. Brief descriptions of the construction methods follow: Table 2. The TBM is designed to support the adjacent soil until temporary (and subsequently permanent) linings are installed. c) Bored This method refers to using a mechanical TBM in which the full face of the tunnel cross section is excavated at one time using a variety of cutting tools that depend on ground conditions (soft ground or rock). Federal Highway Administration 2-11 .1 – Construction Methods a) Cut and Cover This method involves excavating an open trench in which the tunnel is constructed to the design finish elevation and subsequently covered with various compacted earthen materials and soils. b) Shield Driven This method involves pushing a shield into the soft ground ahead. Construction Methods As mentioned previously. Certain variations of this method include using piles and lagging.
f) Sequential Excavation Method (SEM) Soil in certain tunnels may have sufficient strength such that excavation of the soil face by equipment in small increments is possible without direct support. 5. needs to be crossed. the trench may be backfilled with earth to cover and protect the tunnel from the water-borne traffic. This excavation method is called the sequential excavation method. barges.) that prohibit the use of typical cut-andcover techniques for shallow tunnels has been used successfully in recent years. Once excavated. Transit tunnels often do not have an interior finish because the public is not exposed to the tunnel lining except as the tunnel approaches the stations or portals.. The finishes must meet the following standards to ensure tunnel safety and ease of maintenance: • • • • • Be designed to enhance tunnel lighting and visibility Be fire resistant Be precluded from producing toxic fumes during a fire Be able to attenuate noise Be easy to clean. rail lines. which is systematically removed in front of the encroaching tunnel section. this method is often used. Afterward. A brief description of the typical types of tunnel finishes that exist in highway tunnels is given below. and boats.g. Tunnel Finishes The interior finish of a tunnel is very important to the overall tunnel function. Then tunnel sections are constructed in the jacking pit and forced by large hydraulic jacks into the soft ground. Sometimes if the soil above the proposed tunnel is poor then it is stabilized through various means such as grouting or freezing. the soil face is then supported using shotcrete and the excavation is continued for the next segment.Tunnel Maintenance and Rehabilitation Manual e) Immersed Tube When a canal. channel.. e. A trench is dug at the water bottom and prefabricated tunnel segments are made water tight and sunken into position where they are connected to the other segments. g) Jacked Tunnels The method of jacking a large tunnel underneath certain obstructions (highways. The cohesion of the rock or soil can be increased by injecting grouts into the ground prior to excavation of that segment. ships. First jacking pits are constructed. etc. 2-12 Federal Transit Administration . river. etc. This method is considered when the obstruction cannot be moved or temporarily disturbed. buildings.
economical. The Porcelain Enamel Institute (PEI) has established guidelines for the performance of porcelain enamel through the following publications: • Appearance Properties (PEI 501) • Mechanical and Physical Properties (PEI 502) • Resistance to Corrosion (PEI 503) • High Temperature Properties (PEI 504) • Electrical Properties (PEI 505). tiles are 106 mm (4 1⁄4 in) square and are available in a wide variety of colors. Tunnels with a concrete or shotcrete inner lining are conducive to tile placement because of their smooth surface. They differ from conventional ceramic tile in that they require a more secure connection to the tunnel lining to prevent the tiles from falling onto the roadway below.Tunnel Maintenance and Rehabilitation Manual a) Ceramic Tile This type of tunnel finish is the most widely used by tunnel owners. and good reflectors of light due to the smooth. however. and low shrinkage. Federal Highway Administration 2-13 . reflective. The epoxy is a thermosetting resin that is chemically formulated for its toughness. They are not. they are durable. b) Porcelain-Enameled Metal Panels Porcelain enamel is a combination of glass and inorganic color oxides that are fused to metal under extremely high temperatures. Ceramic tiles are extremely fire resistant. fiberglass boards are frequently used. easily washed. strong adhesion. these panels are not good for sound attenuation. Porcelain enamel is typically applied to either cold-formed steel panels or extruded aluminum panels. This method is used to coat most home appliances. tiles may need to be replaced eventually because of normal deterioration. Experience has shown that these coatings do not withstand the harsh tunnel environmental conditions as well as the others. for walls. and come in a variety of colors. The additional amount purchased can be up to 10 percent of the total tiled surface. easily cleaned. As with ceramic tile. Even with a more secure connection. Typically. c) Epoxy-Coated Concrete Epoxy coatings have been used on many tunnels during construction to reduce costs. For ceilings. the panels are often filled with a lightweight concrete. which in new tunnels has been addressed through other means. The attributes of porcelain-enameled panels are similar to those for ceramic tile previously discussed. glazed exterior finish. Additional tiles are typically purchased at the time of original construction since they are specifically made for that tunnel. reflective ability. good sound attenuators. resulting in the need to repair or rehabilitate more often. Durable paints have also been used.
Metal tiles are coated with porcelain enamel and are set in mortar similarly to ceramic tile. ease of replacement. a combination of the two is also possible where the metal panel is applied as a veneer. and ability to capitalize on the benefits of some of the materials mentioned above. Generally ceramic tile is cast into the underside of the panel as the final finish. 2-14 Federal Transit Administration .Tunnel Maintenance and Rehabilitation Manual d) Miscellaneous Finishes There are a variety of other finishes that can be used on the walls or ceilings of tunnels. Some of the systems are listed below: (1) Coated Cementboard Panels These panels are not in wide use in American tunnels at this time. (3) Metal Tiles This tile system is uncommon. however. but has been used successfully in certain tunnel applications. Some of these finishes are becoming more popular due to their improved sound absorptive properties. (2) Pre-cast Concrete Panels This type of panel is often used as an alternative to metal panels. fiber-reinforced cementboard that is coated with baked enamel. but they offer a lightweight.
VENTILATION SYSTEMS 1. Types
Tunnel ventilation systems can be categorized into five main types or any combination of these five. The five types are as follows:
Natural Ventilation Longitudinal Ventilation Semi-Transverse Ventilation Full-Transverse Ventilation Single-Point Extraction.
It should be noted that ventilation systems are more applicable to highway tunnels due to high concentration of contaminants. Rail transit tunnels often have ventilation systems in the stations or at intermediate fan shafts, but during normal operations rely mainly on the piston effect of the train pushing air through the tunnel to remove stagnant air. Many rail transit tunnels have emergency mechanical ventilation that only works in the event of a fire. For further information on tunnel ventilation systems refer to NFPA 502 (National Fire Protection Association). a) Natural Ventilation
A naturally ventilated tunnel is as simple as the name implies. The movement of air is controlled by meteorological conditions and the piston effect created by moving traffic pushing the stale air through the tunnel. This effect is minimized when bi-directional traffic is present. The meteorological conditions include elevation and temperature differences between the two portals, and wind blowing into the tunnel. Figure 2.13 shows a typical profile of a naturally ventilated tunnel. Another configuration would be to add a center shaft that allows for one more portal by which air can enter or exit the tunnel. Many naturally ventilated tunnels over 180 m (600 ft) in length have mechanical fans installed for use during a fire emergency.
Figure 2.13 – Natural Ventilation
Longitudinal ventilation is similar to natural ventilation with the addition of mechanical fans, either in the portal buildings, the center shaft, or mounted inside the tunnel. Longitudinal ventilation is often used inside rectangular-shaped tunnels that do not have the extra space above the ceiling or below the roadway for ductwork. Also, shorter circular tunnels may use the longitudinal system since there is less air to replace; therefore, the need for even distribution of air through ductwork is not necessary. The fans can be reversible and are used to move air into or out of the tunnel. Figure 2.14 shows two different configurations of longitudinally ventilated tunnels.
Figure 2.14 – Longitudinal Ventilation
Semi-transverse ventilation also makes use of mechanical fans for movement of air, but it does not use the roadway envelope itself as the ductwork. A separate plenum or ductwork is added either above or below the tunnel with flues that allow for uniform distribution of air into or out of the tunnel. This plenum or ductwork is typically located above a suspended ceiling or below a structural slab within a tunnel with a circular cross-section. Figure 2.15 shows one example of a supply-air semi-transverse system and one example of an exhaust-air semi-transverse system. It should be noted that there are many variations of a semi-transverse system. One such variation would be to have half the tunnel be a supply-air system and the other half an exhaust-air system. Another variation is to have supply-air fans housed at both ends of the plenum that push air directly into the plenum, towards the center of the tunnel. One last variation is to have a system that can either be exhaust-air or supply-air by utilizing reversible fans or a louver system in the ductwork that can change the direction of the air. In all cases, air either enters or leaves at both ends of the tunnel (bi-directional traffic flow) or on one end only (uni-directional traffic flow).
Figure 2.15 – Semi-Transverse Ventilation
singlepoint extraction can be used to increase the airflow potential in the event of a fire in the tunnel. Both of these methods are rather costly and thus are seldom used. thus providing a larger opening. This method is used primarily for longer tunnels that have large amounts of air that need to be replaced or for heavily traveled tunnels that produce high levels of contaminants. Figure 2. The presence of supply and exhaust ducts allows for a pressure difference between the roadway and the ceiling. This can be done by mechanically opening louvers or by constructing portions of the ceiling out of material that would go from a solid to a gas during a fire. the air flows transverse to the tunnel length and is circulated more frequently.and full-transverse ventilation systems. Figure 2. 2-18 Federal Transit Administration . therefore.16 shows an example of a full-transverse ventilation system. The system works by allowing the opening size of select exhaust flues to increase during an emergency.16 – Full-Transverse Ventilation e) Single-Point Extraction In conjunction with semi. This system may also incorporate supply or exhaust ductwork along both sides of the tunnel instead of at the top and bottom. Newer tunnels achieve equal results simply by providing larger extraction ports at given intervals that are connected to the fans through the ductwork. but it incorporates supply air and exhaust air together over the same length of tunnel.Tunnel Maintenance and Rehabilitation Manual d) Full-Transverse Ventilation Full-transverse ventilation uses the same components as semi-transverse ventilation.
These additional vanes allow the fan to deliver pressures that are approximately four times that of a typical tube axial fan. but the difference between the two is the addition of guide vanes on one or both sides of the impellor for the vane axial fans. Both types move air parallel to the impellor shaft. Centrifugal fans are predominantly located within ventilation or portal buildings and are connected to supply or exhaust ductwork. For tunnel applications. Figure 2. They are commonly selected over axial fans due to their higher efficiency with less horsepower required and are therefore less expensive to operate.Tunnel Maintenance and Rehabilitation Manual 2. Federal Highway Administration 2-19 . The two most common uses of axial fans are to mount them horizontally on the tunnel ceiling at given intervals along the tunnel or to mount them vertically within a ventilation shaft that exits to the surface. Air enters parallel to the shaft of the blades and exits perpendicular to that. centrifugal fans can either be backward-curved or airfoil-bladed.17 – Axial Fans (2) Centrifugal This type of fan outlets the air in a direction that is 90 degrees to the direction at which air is obtained. Equipment a) Fans (1) Axial There are two main types of axial fans—tube axial fans and vane axial fans.
This can be achieved by installing cylindrical or rectangular attenuators either mounted directly to the fan or within ductwork along the system. They can be operated at either constant or variable speeds depending on the type of motor. (4) Dampers Objects used to control the flow of air within the ductwork are considered dampers. but can also be operated at some position in between to regulate flow or pressure within the system. Direct drives are where the fan is on the same shaft as the motor. chains. The type of drive used can also induce speed variability for the ventilation system. Indirect drives allow for flexibility in motor location and are connected to the impellor shaft by belts. They are typically used in a full open or full closed position. (3) Sound Attenuators Some tunnel exhaust systems are located in regions that require the noise generated by the fans to be reduced.Tunnel Maintenance and Rehabilitation Manual Figure 2. 2-20 Federal Transit Administration . or gears. According to the National Electric Manufacturers Association (NEMA). motors should be able to withstand a voltage and frequency adjustment of +/.18 – Centrifugal Fan b) (1) Supplemental Equipment Motors Electric motors are typically used to drive the fans.10 percent. (2) Fan Drives A motor can be connected to the fan either directly or indirectly.
The individual tunnel owners usually stipulate the required level of lighting within the tunnel. Types a) Highway Tunnels There are various light sources that are used in tunnels to make up the tunnel lighting systems. as a minimum. may be used.Tunnel Maintenance and Rehabilitation Manual C. Therefore. a certain length of brighter lights is necessary at the entrances to the tunnels. and pipe lighting. metal halide. light levels should be of such a magnitude that inspectors or workers at track level could clearly see the track elements without using flashlights. Both high-pressure sodium lamps and metal halide lamps are also typically used to line the entire length of roadway tunnels. Shorter tunnels will require less daytime lighting due to the effect of light entering the portals on both ends. LIGHTING SYSTEMS 1. At the ends of the roadway tunnel. lowpressure sodium lamps or high-pressure sodium lamps are often combined with the fluorescent lights to provide higher visibility when drivers’ eyes are adjusting to the decrease in natural light. The transition length of tunnel required for having a higher lighting capacity varies from tunnel to tunnel and depends on which code the designer uses. whereas longer tunnels will require extensive lighting for both nighttime and daytime conditions. These include fluorescent. such as tile or metal panels. In conjunction with the lighting system. high-pressure sodium. Federal Highway Administration 2-21 . In addition. usually consisting of high-pressure sodium or metal halide lamps and longitudinal acrylic tubes on each side of the lamps. which is a system that may use one of the preceding light source types. Systems are chosen based on their life cycle costs and the amount of light that is required for nighttime and daytime illumination. Fluorescent lights typically line the entire roadway tunnel length to provide the appropriate amount of light. low-pressure sodium. pipe lighting. are used to disperse light uniformly along the tunnel length. However. a highly reflective surface on the walls and ceiling. b) Rail Transit Tunnels Rail transit tunnels are similar to highway tunnels in that they should provide sufficient light for train operators to properly adjust from the bright portal or station conditions to the darker conditions of the tunnel.
but may be made of precast reinforced concrete or fiber reinforced plastic. c) Fasteners/Bolts/Spikes These fasteners include a spike. bolt. OTHER SYSTEMS/APPURTENANCES 1. b) Rail Joints Rail joints are mechanical fastenings designed to unite the abutting end of contiguous bolted rails. • Help keep the two rails at the correct relative elevation. • Maintain a fixed distance between the two rails making up a track. e) Crossties Crossties are usually sawn solid timber. • Hold fasteners that can resist rail rotation due to laterally imposed loads. They assist in holding the rails to gage. The many functions of a crosstie are to: • Support vertical rail loads due to train weight. • Provide a convenient system for adjusting the vertical profile of the track. and provide a more desirable positioning of the wheel bearing area on the rail head. • Distribute those loads over a wide area of supporting material. d) Tie Plates Tie plates are rolled steel plates or a rubberized material designed to protect the timber crosstie from localized damage under the rails by distributing the wheel loads over a larger area. or another mechanical device used to tie the rail to the crossties. 2-22 Federal Transit Administration . steel-shape portion of the track to be laid end-to-end in two parallel lines that the train or vehicle’s wheels ride atop.Tunnel Maintenance and Rehabilitation Manual D. • Anchor the rails against both lateral and longitudinal movement by embedment in the ballast. Track The track system contains the following critical components: a) Rail The rail is a rolled. tilt the rails inward to help counteract the outward thrust of wheel loads.
These pads are placed at close intervals and permit the rail to span directly from one pad to another. and maintain proper cross-level surface and alignment. and vertically under dynamic loads imposed by railroad rolling equipment and thermal stresses exerted by the rails. (1) Steel Contact Rail Steel contact rail is the rail that carries power for electric rail cars through the tunnel and is placed parallel to the other two standard rails.19 and 2. (4) Protection Board Brackets Protection board brackets are mounted on either timber ties or concrete ties/base and are used to support the protection board at a distance above the steel contact rail. Power (Third Rail/Catenary) a) Third Rail Power System A third rail power system will consist of the elements listed below and will typically be arranged as shown in Figures 2. (2) Contact Rail Insulators Contact rail insulators are made either of porcelain or fiberglass and are to be installed at each supporting bracket location. (3) Protection Board Protection boards are placed above the steel contact rail to “protect” personnel from making direct contact with this rail.20. The ballast is used to transmit and distribute the load of the track and railroad rolling equipment to the subgrade.Tunnel Maintenance and Rehabilitation Manual f) Ballast Ballast is a coarse granular material forming a bed for ties. usually rocks. longitudinally. restrain the track laterally. g) Plinth Pads Plinth pads are concrete support pads or pedestals that are fastened directly to the concrete invert. 2. provide adequate drainage for the track. Federal Highway Administration 2-23 . These boards are typically made of fiberglass or timber.
6 km (1 mile).20 – Typical Third Rail Insulated Anchor Arm 2-24 Federal Transit Administration . with a maximum length for any section limited to 1.19 – Typical Third Rail Power System (Note: Dimensions indicate minimum clearance requirements) Figure 2.Tunnel Maintenance and Rehabilitation Manual (5) Third Rail Insulated Anchor Arms Third rail insulated anchor arms are located at the midpoint of each long section. Figure 2.
wires. cable vaults. pull boxes. pull-off arrangements. relay rooms. switch circuit controllers. and local control facilities. disconnects. Since the methods used to support a catenary system within a tunnel can vary. signal power cables. Part 2 provides inspection procedures for various components listed above that may exist in a tunnel catenary system. underbridge assemblies. For inspection purposes. signal cases. Chapter 4. Examples of these systems would be emergency phones that are located periodically along a highway tunnel and radios by which train controllers correspond with each other and central operations. transformers. hangers. section insulators. Section D. For tunnel catenary systems. Federal Highway Administration 2-25 . This is particularly true for the methods of support in that the catenary system is supported directly from the tunnel structure instead of from poles with guy wires. insulators. messenger supports. 3. clamped electrical connectors. yoke plates.Tunnel Maintenance and Rehabilitation Manual b) Catenary Power System The catenary system is an overhead power system whereby the rail transit cars are powered by means of contact between the pantographs on top of the rail car and the catenary wire. switch machines. The specific components included in a communication system include the phones and radios. messenger systems. jumpers. as well as any cables. overlaps. duct banks. phase breaks. registration assemblies. back guys and anchors. steady arms. express cables. A typical signal system may consist of some or all of the following components: signals. Signal/Communication Systems a) Signal System The signal system is a complex assortment of electrical and mechanical instruments that work together to provide direction for the individual trains within a transit system. a detailed description of the individual components is not given in this section. contact wires. or other equipment that is needed to transport the messages. some of the above components are not necessary or are modified in their use. and section disconnects. safety assemblies. local cables. A typical catenary system may consist of some or all of the following components: balance weights. b) Communication System The communication system consists of all devices that allow communication from or within a tunnel.
Tunnel Maintenance and Rehabilitation Manual 2-26 Federal Transit Administration .
Aside from predicting structural defects.Tunnel Maintenance and Rehabilitation Manual CHAPTER 3: PREVENTIVE MAINTENANCE A. The primary reason for performing tunnel washing is to maintain proper tunnel luminance. Chapter 4 deals with methods for repairing such structural defects. rinse tunnel with water using highpressure jets. 2. 1. tunnels with a lower ADT would not accumulate dirt as quickly and can be washed less frequently. A description of each maintenance task is provided below. be washed according to the following procedure: first. which is dependent on the reflectivity of the tunnel finish.. etc. spray tunnel with water or a water/detergent mixture if permitted and scrub with mechanically rotating brushes. there are other preventive maintenance tasks that can be performed regularly to ensure safe operation of the tunnel. second. Since most of the dirt is from vehicle exhaust and tire spray. The frequency of this procedure may vary for each tunnel owner and depends on environmental conditions. It is recommended that washings be suspended during winter months for tunnels that are located in a region where wintertime temperatures are below freezing. it is important that regular in-depth inspections be performed in which structural defects are identified and subsequently scheduled for repair based upon their severity. such as ceramic tile. Another factor in determining frequency would be the average daily traffic (ADT) that uses the tunnel. These tasks include: • • • • Tunnel Washing Drain Flushing Ice/Snow Removal Tile Removal. Drain Flushing Roadway drain inlets or drainage troughs in the case of direct fixation track should be kept free of debris and should be flushed with water to verify that drains are operating Federal Highway Administration 3-1 . Tunnel Washing It is recommended that highway tunnels that utilize an interior finish. porcelain enameled panels. PREVENTIVE MAINTENANCE OF THE TUNNEL STRUCTURE The primary objectives of incorporating regular preventive maintenance procedures into the tunnel structure and its systems are to provide a safe and functional environment for those who work in or travel through the tunnel and to extend its useful life. Since it is usually not possible to have advance knowledge of where structural defects will occur. because reflectivity of the surface is not critical. Highway tunnels with unfinished surfaces (bare concrete or exposed rock) and rail transit tunnels do not typically require washings.
ice forms at locations of active leakage. it is paramount that they be well maintained to prevent unforeseen breakdowns. and cost data for use in properly predicting the life-cycle costs for a particular piece of equipment. To assist in this process. If a computerized database system is used. Often. replacement. it is essential that proper plowing be performed and deicing agents be applied to maintain safe traveling conditions. Another time of identifying and removing possible loose tiles is during the monthly tunnel washing procedure. 3. 3-2 Federal Transit Administration . Ice/Snow Removal In regions where the temperature within the tunnel drops below freezing. As can be expected. it is critical that deicing agents be used to prevent accumulation of ice that could present a danger to automobile traffic or tunnel personnel using the safety walk. Any new areas should be noted and added to the list of areas to be inspected on a quarterly basis. When such ice could build up on the roadway or safety walk. areas of loose tiles should be identified and those that are in danger of falling should be removed.Tunnel Maintenance and Rehabilitation Manual correctly. To achieve this goal. B. it can be performed concurrently with tunnel washing since the flushing equipment will be available. Tile Removal During an in-depth inspection. It is recommended that those loose tiles. be inspected on a quarterly basis to determine if more tiles need to be removed to ensure safety to the motorist. Any tiles that are removed should be scheduled for replacement. many of which must work together for the overall systems to function properly. For highway tunnels. it is suggested that the tunnel be inspected daily to observe and to take action to mitigate such leakage. 4. PREVENTIVE MAINTENANCE OF MECHANICAL SYSTEMS The tunnel mechanical systems are comprised of multiple individual components. it would have the capability of storing historical repair. which remain. in similar regions where snow and ice may accumulate for a certain distance within the tunnel from the portals. Also. This should be done on a semi-annual basis. During these potential icing conditions. multiple computerized database systems have been developed that can be adapted to a particular tunnel owner’s needs. it is recommended that a routine preventive maintenance program be developed that includes every major piece of equipment and that work orders be generated on a set schedule for the tasks that are to be performed. Since these overall systems are critical for providing a safe environment for the tunnel users and staff. the frequency of such a task is dependent on the natural conditions that produce the snow and ice. tiles will become dislodged during the scrubbing or pressure washing of the tunnel.
location. Federal Highway Administration 3-3 . Also.Tunnel Maintenance and Rehabilitation Manual It is impossible for the scope of this manual to incorporate preventive maintenance procedures for every conceivable piece of equipment. For this reason.1 lists the preventive maintenance functions for each of the major pieces of equipment or mechanical systems along with the suggested frequency for performing the preventive maintenance. particularly if it differs from that given below. Table 3. newer tunnels and tunnels yet to be built may incorporate new technologies that to date have not been addressed. the major components of the mechanical systems are included. whereas. it is always necessary to follow the manufacturers’ suggested preventive maintenance procedures for a given piece of equipment. however. Many tunnels may not utilize all of the components listed due to their size. or age. it should be noted that the preventive maintenance functions given are sometimes general and therefore should be made specific to the actual equipment that exists in a particular tunnel.
1 – Preventive Maintenance of Mechanical Systems 3-4 Federal Transit Administration .Tunnel Maintenance and Rehabilitation Manual Table 3.
Tunnel Maintenance and Rehabilitation Manual Federal Highway Administration 3-5 .
Tunnel Maintenance and Rehabilitation Manual 3-6 Federal Transit Administration .
Tunnel Maintenance and Rehabilitation Manual Federal Highway Administration 3-7 .
many individual components make up the tunnel electrical systems. in their Maintenance Testing Specifications (MTS-2001). For this reason.2 lists the preventive maintenance functions for each of the major pieces of equipment or electrical systems along with the suggested frequency for performing the preventive maintenance. one difference is that many of the electrical components are interconnected and rely on each other for proper functioning of the entire system. only the major components of the electrical systems are included herein. it is recommended that an outside electrical testing agency be contracted that meets the requirements of NETA full membership. Given the importance of an electrical system that is constantly being used and is vital for the overall safety of the tunnel.Tunnel Maintenance and Rehabilitation Manual C. Appendix B of MTS-2001 provides recommended frequencies for maintenance procedures that are comparable to what is given in this section. Additionally. Also. Another reference is the National Fire Protection Association’s NFPA 70B: Recommended Practice for Electrical Equipment Maintenance. a switching procedure and one-line safety diagrams of the electrical system should be prepared and posted in all electrical rooms. or age. it is always necessary to refer to the manufacturers’ suggested preventive maintenance procedures for a given piece of equipment. location. Also. including but not limited to NFPA 70E: Standard for Electrical Safety Requirements for Employee Workplaces. the electrical preventive maintenance functions given are sometimes general and should be made specific to the actual equipment that exists in a particular tunnel. As with the mechanical preventive maintenance functions. whereas. newer tunnels and tunnels yet to be built may incorporate new technologies that to date have not been addressed. If the tunnel owner does not have qualified in-house personnel. PREVENTIVE MAINTENANCE OF ELECTRICAL ELEMENTS Similar to tunnel mechanical systems. Many tunnels may not utilize all of the components listed due to their size. More specifically. However. Table 3. the electrical systems could be viewed with higher importance because the mechanical systems and other tunnel systems need electricity for them to function properly. For the procedures given below to be performed efficiently and safely. 3-8 Federal Transit Administration . it is suggested that the preventive maintenance system that was recommended for the mechanical systems be adapted to include preventive maintenance functions for the electrical systems. As with the mechanical systems. the InterNational Electrical Testing Association (NETA). provides detailed information and guidelines regarding maintenance of electrical equipment. it is recommended that in-house maintenance staff be trained in the current Occupational Safety and Health Administration (OSHA) and NFPA standards.
2 – Preventive Maintenance of Electrical Systems Federal Highway Administration 3-9 .Tunnel Maintenance and Rehabilitation Manual Table 3.
Tunnel Maintenance and Rehabilitation Manual 3-10 Federal Transit Administration .
Tunnel Maintenance and Rehabilitation Manual Federal Highway Administration 3-11 .
Tunnel Maintenance and Rehabilitation Manual 3-12 Federal Transit Administration .
Tunnel Maintenance and Rehabilitation Manual Federal Highway Administration 3-13 .
Tunnel Maintenance and Rehabilitation Manual 3-14 Federal Transit Administration .
a) Rail Lubrication It is commonly known that periodic lubrication of curves can extend rail life. Federal Highway Administration 3-15 . Track Safety Standards Part 213 Subpart A to F. Listed below are several preventive maintenance procedures that are recommended to prolong the working life of the track and the supporting structure. or by railcar-mounted lubricant sticks that apply a thin coat of grease to the gage face during train operation. The frequency of this procedure is dependent upon the amount of gross tonnage traveling over the track and can range from one year for track with very high tonnages to five years for track with low tonnages. This oil can be applied using a spray machine. In fact. Class of Track 1-5 (TSS Part 213) be used. This does not detract from the importance of proper documentation of the inspection process. it is important that some internal guidelines be followed to ensure accuracy and consistency of repairs or new installations. by the use of wayside lubricators (a train actuated device that first applies the lubricant to the wheel flanges and then subsequently to the rail). If items are going to be repaired or replaced.Tunnel Maintenance and Rehabilitation Manual D. Additionally. PREVENTIVE MAINTENANCE OF TRACK SYSTEMS 1. The application can be performed by hand. This serves as a means of preventing any further degradation that could occur before a scheduled maintenance is performed. it just allows for certain simple procedures to be performed immediately after the condition is discovered. Track and Supporting Structure The track and its supporting structure should be inspected more frequently than other systems within a tunnel. performing scheduled “out-of-face” grinding and profile grinding of the rail head can help prevent the development of surface defects by optimizing the rail-wheel interaction. The procedure can also be performed if excessive wear is identified during a routine inspection or if noise abatement is desired. b) Rail Grinding In addition to removing defects that are identified using specialized rail defect detection equipment. asphalt based dipping oil should be applied to tie plates and spikes when they are subjected to corrosive conditions. The lubricant should be placed on the gage face of the rail. the tasks of inspection and preventive maintenance may often overlap in order to make efficient use of the inspection and maintenance staff and equipment. with care taken to minimize the amount of lubricant to prevent migration to the top of the rail head. The frequency of this procedure is based on durability or life expectancy of the lubricant used and the amount of train traffic to which the rail is subjected. In lieu of such guidelines it is recommended that the USDOT’s Federal Railroad Administration – Office of Safety’s Code of Federal Regulations for Title 49.
It is recommended that the initial retightening be performed one to three months after installation and all subsequent retightening be done on an annual basis.000 lb) per bolt for the initial tightening of a new bolt and between 6. or being fouled with silt carried by the water infiltration. If known areas exist where the ballast is either being eroded or undermined by water flow. then a new coating should be applied.000 and 25. the ballast is not subjected to the sedimentation of fine particles within the voids due to excessive vegetation growth. e) Joint Maintenance All joints should be fully bolted and the bolts should be retightened as required within a range of 9. The ballast can be removed and cleaned using a ballast cleaner and subsequently replaced.070 to 13. if severe water infiltration exists. the general vertical and horizontal alignment should be periodically adjusted to conform to specified standards.800 to 11. f) Regaging As gage deficiencies are identified during inspection. d) Tie Renewals A routine program of replacing crossties that do not meet inspection standards should be implemented to ensure that the proper number of quality crossties are located within each length of rail. if initial petrolatum or petrolatumbased compound for preserving the joint is deficient. certain tasks can be periodically performed in lieu of addressing the water infiltration problem using methods given in Chapter 4. This can be accomplished by using automatic track aligning equipment for ballasted track or by manually raising and lining direct fixation track and placing shims under the rail plates as necessary. however. The spray method can be used so that the integrity of the joint is not disturbed.610 kg (20.000 to 30. the ballast can be negatively impacted in a localized area. Also.000 lb) per bolt for all subsequent retightening. The entire ballast section along the tunnel should be maintained at all times. 3-16 Federal Transit Administration . or a new layer of ballast (track surfacing) can be applied to the affected area and tamped to match the specified cross section.400 kg (15. regaging should be performed if changes in gage are severe or abrupt.Tunnel Maintenance and Rehabilitation Manual c) Ballast Cleaning/Replacement Within a tunnel. g) General Aligning Independent of whether the track structure is direct fixation or ballasted construction.
For that reason. Periodically clean rail insulators to prevent stray current from entering the ground or supporting structures and increasing the amount of corrosion. the spike will most likely need to be replaced on a routine basis. chipped. or otherwise deficient sheds on all insulators. Possible procedures to accomplish this are listed below. Federal Highway Administration 3-17 . • Replace broken. Repair/replace splices and joints that could be impeding the current flow for the contact rail or redirecting flow causing stray current corrosion. The normal life expectancy of 25 years for spikes can be as little as 6 months if stray current corrosion is occurring in combination with the presence of moisture. it is necessary to perform regular preventive maintenance in addition to the periodic visual and in-depth inspections that are presented in the complementary Tunnel Inspection Manual. • • • • Perform general aligning on third rail to ensure consistency with the running rails alignment. Power (Third Rail/Catenary) a) Third Rail System The proper operation and efficiency of third rail power systems is crucial to those tunnel track segments that contain them.Tunnel Maintenance and Rehabilitation Manual h) Spike Replacement If it is suspected that stray current corrosion is occurring in a tunnel. Apart from major repairs or complex preventive maintenance tasks. 2. many of the suggested procedures below can be performed at the same time as the in-depth inspections in order to minimize disruption to the system’s schedule. catenary systems are crucial for the proper operation of the transit systems that utilize them. it is beneficial to perform routine inspections of the systems as outlined in the complementary Tunnel Inspection Manual and also to conduct routine preventive maintenance of certain elements that make up the third rail system. b) Catenary System Similar to the third rail power systems. Therefore. This is especially true in wet environments near portals or areas of water infiltration within the tunnel since moisture also advances the onset of corrosion. Repair/replace deficient protection boards and brackets to ensure that they do not interfere with connections to the train or fail to provide safety to tunnel personnel.
Signal/Communication Systems Signal/communication systems relate directly to the overall safety of the rail transit system. clear debris from path of moving components. so does the dependence on a reliable efficient method for maneuvering the cars through the system and for communicating with them during that process or during emergencies. Adjust turnbuckles on hangers of section insulators to keep units level. clean. it is recommended that a routine program be implemented to lubricate moving components. Two types of corrosion protection exist: cathodic protection and stray current protection. Corrosion Protection Systems Corrosion protection systems may be used in either highway or rail transit tunnels. Since a majority of the components that make up these systems are electric or electronic. PREVENTIVE MAINTENANCE OF MISCELLANEOUS APPURTENANCES 1. Replace segments of contact wire with vertical thickness less than 10. and full section overlap jumpers that have signs of corrosion or burning. On the other hand. feeder points. A description of each of these systems is provided below. Remove. or the rail system itself) from deteriorating prematurely due to corrosion resulting from the presence of any aqueous electrolyte. Corrosion from electrolysis is specifically prevalent in areas where moisture is present and where there are dissimilar metals attached together.7 mm (0. 3-18 Federal Transit Administration . Most problems with this equipment are identified during a routine inspection and thus can be fixed immediately or scheduled for immediate action. a) Cathodic Protection Systems Cathodic protection systems are designed to protect any metal components of the tunnel structure or other systems (such as buried pipelines. 3. Apply high melting point grease to all stranded conductors. However. there are mechanical devices that are operated manually or by electric power that should be consistently maintained. As ridership and train frequencies increase.42 in). surrounding buildings. Adjust contact wires at overlaps for proper matching alignment. E. and tighten “C” jumpers. and replace light bulbs in crucial equipment. their proper operation is or can be tested continuously.Tunnel Maintenance and Rehabilitation Manual • • • • • Align hangers to vertical position and rectify condition that may have caused hangers to be out of alignment.
the manufacturer’s recommended maintenance procedures will always take precedence over any recommendations given in this section. Perform electrical measurements (voltage and current) and inspection of a cathodic protection system annually.Tunnel Maintenance and Rehabilitation Manual These systems may be as simple as providing connections between metal components and the ground so that electrolysis does not take place in the criticalmetal components. and wiring. Identify areas that may be affected by future or ongoing construction. Make required adjustment to accommodate changes. passive cathodic protection systems with anodes buried in the ground. wiring. safety. Locate areas of inadequate protection levels. ensure that any test equipment is in good operating condition and that the calibration effective period has not expired. All impressed current protective devices (protective relays. The electrical measurements and inspection will be performed to: • • • • • • • • Make certain that protection is being provided in accordance with established criteria in the design documents. This section recommends maintenance procedures for effective and efficient operation of cathodic protection systems. Perform semi-annual inspection and testing of the following cathodic protection equipment: • • • All impressed current sources (rectifiers and power supplies). Also. and lightning protection). Also. circuit breakers. can be used to sacrificially attract the stray current away from the critical metal components. specific cathodic protection components will vary from one tunnel to another depending on the how the original design provided protection. Federal Highway Administration 3-19 . and economic considerations. Assess the effectiveness of isolated joints and continuity jumpers to achieve proper isolation. for complex electrical components such as rectifiers. diodes. fuses. Adjust frequency of test and inspections to reflect changes to field conditions. fuses. Select areas to be monitored more frequently. Provide additional equipment as needed to maintain an effective cathodic protection system. Another method is to counterbalance the effects of stray current by inducing an impressed current using rectifiers. Therefore. Any testing of the cathodic protection effectiveness shall be performed in accordance with the National Association of Corrosion Engineers (NACE) Internationals’ recommended practices and procedures. As with other systems. Reverse current switches.
Railings. Do not allow water or ice to accumulate on these surfaces to prevent users from slipping and falling. older tunnels may require that the DC systems be modified or retrofitted to eliminate corrosion resulting from DC stray currents. Safety Walks. be properly maintained such that they will be able to support the pedestrian loadings during their use. Stray Current Protection Systems Stray current occurs within DC electrified rail transit systems and in conjunction with moisture from water infiltration. Aside from the above measures. and Exit Stairs/Ladders It is important to ensure that tunnel elements such as safety walks. most new DC traction power systems in tunnels are designed to minimize leakage of DC stray currents. Repair or replace any defective components of the cathodic protection system. Clean and coat as required to provide isolation. Repair or replace any defective isolating device. and reducing the amount of moisture present in the tunnel by addressing the water infiltration problem (as described in Chapter 4. Sufficient testing should be performed following any adjustment to the cathodic protection system to assure proper protection to the tunnel structure and that no adverse effects will occur to other nearby structures. Do not use stairs or walkways as storage space.Tunnel Maintenance and Rehabilitation Manual Other remedial tasks that may be performed on the cathodic protection system could include the following: • • • • • • • Replace anodes per manufacturers’ criteria. Replace defective wiring. Repair or replace jumpers. 3-20 Federal Transit Administration . 2. Remove any accidental metallic contact. This can be accomplished by providing the following preventive maintenance functions: • • • Keep areas clean and free of debris. b. can cause significant amounts of corrosion of tunnel and rail components. However. Section A). Ensure that steel structures are adequately painted or pre-conditioned to prevent corrosion and subsequent reduction in load carrying capacity. railings and exit stairs/ladders that are accessed either by tunnel personnel or tunnel occupants in the event of an emergency. The risk of stray current corrosion can be reduced by increasing the resistance of the leakage path to the earth through increasing rail insulation.
ventilation structures are often utilized in urban settings where tunnel intake or exhaust occurs through grates in the sidewalk or street above the tunnel. which could be constructed from any of the same materials available for tunnel construction.Tunnel Maintenance and Rehabilitation Manual • • • Consider coating concrete or steel walking surfaces with an anti-slip finish. then they can be repaired using techniques given in Chapter 4. Federal Highway Administration 3-21 . Subsequently. Ensure that all metal components are isolated from any electrification system. which could pose a safety hazard to pedestrians walking across the grating. a preventive maintenance program should be instituted to ensure the following: • • • Keep areas clean and free of debris. the air travels though a shaft structure that extends to the depth of the tunnel. Maintain all doors or gates to guarantee proper operating condition. Maintain grates at top of vent structures to prevent corrosion and dislodging. do not lock doors or gates that are necessary for emergency exit. 3. Do not use as storage spaces. If the routine inspection identifies structural deficiencies in this shaft or in emergency egress shafts. Otherwise. Ventilation Structures and Emergency Egress Shafts In rail transit systems. Perform maintenance on any fans at top of vent structures as described in Section B of this chapter. Also.
Tunnel Maintenance and Rehabilitation Manual 3-22 Federal Transit Administration .
controlling water infiltration is of great concern to tunnel owners. a detailed explanation of the different types of concrete deficiencies and methods for their repair is provided in Section B. substandard construction. A. As ground water flow patterns change over time and drains become clogged with sediment. Section C addresses the issue of repair for specific types of liner construction. Water infiltration is the most common cause of deterioration. water infiltration is the underlying cause of most deterioration of the tunnel structure and components. Even tunnels that are designed to be waterproof. WATER INFILTRATION 1. deficiencies could be the result of substandard design or construction. the method of repair could vary.Tunnel Maintenance and Rehabilitation Manual CHAPTER 4: REHABILITATION OF STRUCTURAL ELEMENTS This chapter describes various methods for repairing specific deficiencies in structural elements within a tunnel. Due to the fact that there are different causes for the degradation. the water is bound to find its way into the tunnel through joints or structural cracks. This could cause a tunnel that was designed to be above the water table to experience hydrostatic forces that it is unable to resist and subsequently water infiltration becomes a problem. In addition. can develop leaks due to inadequate connection/joint design. Federal Highway Administration 4-1 . Water infiltration can occur in all types of tunnel construction. Most tunnels are designed with the foreknowledge that water will exist in the ground. Consequently. Another common reason for repairs is the fact that many tunnels have outlived their designed life expectancy and therefore the construction materials themselves are degrading. but it is prevented from entering the tunnel by providing drainage mechanisms around the exterior of the lining or embedded within the joints. such as immersed tube tunnels that are placed in a trench at the bottom of a body of water. and deterioration of the waterproof lining due to chemical or biological agents in the water or from tears caused by tunnel settlement. or the result of unforeseen or changing geologic conditions in the ground that supports the tunnel. Problem Since many tunnels are constructed deep in the ground and often below the groundwater table. Another scenario that may occur in a few urban settings is that the elevation of the ground water table may rise due to the accumulating effects of basements of surrounding buildings being made relatively waterproof and the city’s water supply needs being met by reservoirs many km (miles) away instead of through groundwater extraction. This chapter provides in-depth discussions and recommendations for repairing tunnels that are being deteriorated by water infiltration (Section A). However.
Most tunnels have problems that fall somewhere in between. which may be undesirable. lights. creating voids behind the liner. 4-2 Federal Transit Administration .8 gpm per 1000 linear feet) of tunnel. The negative consequences can vary from minor surface corrosion of tunnel appurtenances to major deterioration of the structure and thus decreased load carrying capacity of the tunnel. Reinforcement steel with poor or inadequate cover corrodes and causes delamination and spalling of the concrete cover. they set a limit of 0. Road salts carried by vehicles into highway tunnels. which can cause settlement of surrounding structures and/or cause eccentric loading on tunnel that can lead to unforeseen stresses. Consequences of Water Infiltration As can be expected. Steel segmental liners or steel plates can experience section loss if exposed to both moisture and air.2 gpm per 250 linear feet) of tunnel. These fine particles can also clog drains in or behind the lining. Other tunnel owners have adopted this criteria while still others may use a limit of 3. Water may freeze on roadway and safety walks or form icicles from the tunnel crown.Tunnel Maintenance and Rehabilitation Manual It should be noted that in the 1960s some tunnel owners began to develop maximum allowable rates of water infiltration to be used as a guide to determine original design and subsequent repairs if the amount of infiltration increases.8 liters/ minute per 300 linear meters (1 gpm per 1000 linear feet) of tunnel. Masonry units and mortar can be very susceptible to water deterioration and can swell or become brittle depending on chemicals in water. Frozen drains can cause ground water to find or create a new location to enter the tunnel. along with the presence of infiltrated water. Bolts that connect segmental linings can corrode and fail.) can corrode and pose danger to a motorists or trains traveling through the tunnel. • • • • • • • • • • • Cement and sometimes aggregates of concrete liners are eroded causing the structure to be weakened. One such owner was the Bay Area Rapid Transit (BART) system in California. Fasteners of interior finishes or other appurtenances (fans. 2.1). These limits are for reference purposes only.8 liters/minute per 75 linear meters (0. can increase deterioration of the structure. all of which endanger tunnel users (Figure 4. Fine soil particles can be carried through cracks with the water. with the main emphasis for determining repair needs placed on the location of the leak and the condition of the tunnel components that are affected. nothing positive occurs when water infiltrates into a tunnel. Rate of corrosion for tunnel components of rail transit tunnels can be increased by the presence of stray current from electrified traction power systems. etc. especially the invert. This translates to 3 liters/minute per 300 linear meters (0. Below is a list of possible forms of tunnel degradation or safety risks that can result from water infiltration.
there are three options that a tunnel owner must consider for remediation of a water infiltration problem. a) Short Term Repairs For certain situations. long term repairs or. will not be able to stop the water infiltration completely without a total restoration or reconstruction of the tunnel lining or at least significant portions Federal Highway Administration 4-3 .Tunnel Maintenance and Rehabilitation Manual Figure 4. For guidance in this effort. reconstruct all or portions of the tunnel lining that is causing the problem using methods of waterproofing that incorporate newer technologies. a brief explanation of life-cycle-cost methodology is given in Appendix A. a specific cost analysis should be performed that considers the costs over the life of the tunnel. Remediation Methods In general. It should be noted that the alternative classifications are given for descriptive purposes and that overlaps between them do exist. 3. it might be necessary to redirect infiltrated water to the tunnel drainage system on a temporary basis until further investigation can be performed and a more long term solution implemented. whether due to deficiencies in design or construction or a change in the ground water table. The third option will not be discussed in as much detail as the first two but will include a brief discussion of some current technologies being used on new tunnel construction. a more detailed development of the current methods and some associated details will be given.1 – Ice formation at location of water infiltration in plenum area above ceiling slab. To determine the most cost efficient method of repair for a particular situation. The three alternatives are: short term repairs. as a last resort. Since the first and second alternatives are the most common and usually most cost effective. It should be noted that certain tunnels.
A similar method utilizing metal drainage troughs is sometimes used to redirect isolated areas of infiltration to the drainage system. some tunnels may have to rely on a long term system that conveys the water rather than prevents the water from entering the tunnel. Therefore.Tunnel Maintenance and Rehabilitation Manual where water infiltration is a problem. but the following paragraphs cover a few methods for temporarily diverting the infiltrated water. then neoprene rubber sheets can be attached to the tunnel lining with aluminum channels. The sheets can be directed to channel the water to the side of the tunnel where it can flow into the tunnel drainage system (Figure 4.2). Long term systems will be discussed more in-depth in the next section of this chapter. (2) Plastic Pipe Network Another rather rudimentary method is to use plastic piping with one end inserted into the concrete at the main concentration of the leak. 4-4 Federal Transit Administration . (1) Drainage Troughs If leaks are occurring in joints at the tunnel crown in a direction perpendicular to the tunnel length. Figure 4.3). The piping can be hooked together in a network that conveys the water to the primary drainage system (Figure 4.2 – Temporary drainage systems comprised of neoprene rubber troughs and 25 mm (1 in) aluminum channels.
the method of preparing the surface and the procedure for installing the waterproofing system should be investigated to help determine which system should be used. but that does not necessarily mean that the method utilized was the problem. b) Long Term Repairs Since water infiltration is an ongoing problem for tunnel owners. and the cause and exact location of the leak.Tunnel Maintenance and Rehabilitation Manual Figure 4. Many different factors are involved in determining which method should be used that are site specific in that the cause and volume of the water infiltration will help determine how to properly prevent it. The following paragraphs describe a few methods that have been used to address water infiltration problems for the long term. will help determine how to address the problem. Also. Multiple techniques have not performed favorably over the long term. along with knowing the type and condition of the materials that make up the tunnel lining structure. (1) Insulated Panels Insulated panels have been successfully used to line exposed rock tunnels to allow the water to flow behind the insulation down to the Federal Highway Administration 4-5 .3 – Temporary drainage system comprised of 50 mm (2 in) plastic pipe. there have been a wide variety of methods and materials used to prevent the water from entering the tunnel and causing undesirable degradation. it is suggested that a detailed study be performed on major leaks to determine the source and amount of water leakage. This. One method might work very well for one tunnel but not another. Therefore.
It should be noted that use of this type of system would reduce the interior clearances within the tunnel. while being insulated to prevent water from freezing. without projections that could potentially puncture the membrane.9 m (3 ft) square grid (Figure 4. such as shotcrete or other fire-retardant and protective materials. It is suggested that mock-up trials be performed to ensure that the components of the system achieve adequate bond to each other. 2. a continuous.4).5 for a detail of this system. followed by a layer of material that will protect the membrane. especially the application 4-6 Federal Transit Administration .4 m by 9. The term geotextile stands for a wide variety of materials which are normally synthetic and whose main purpose are to provide a drainage gallery outside the waterproofing membrane through which the infiltrating water can freely pass. flexible membrane can be used as the waterproofing layer that allows the water to flow towards the main tunnel drainage system. Figure 4.4 – Insulated panels used as a waterproofing lining to keep infiltrating water from freezing. The geotextile layer also provides a physical protection of the waterproofing membrane. (Photo courtesy of Tunnels & Tunnelling International) (2) Waterproofing Membrane As an addition to the method given above.6 m (8 ft by 32 ft) panels of Ethafoam insulation that was secured to the rock using 12 mm (1⁄2 in) diameter galvanized steel pins set into the rock on a . The specific process that has been effectively used involves placing a geotextile material against the existing tunnel interior. Refer to Figure 4. then a PVC waterproofing membrane.Tunnel Maintenance and Rehabilitation Manual primary drainage system. This system requires a relatively smooth surface to attach the membrane to. An example of this installation is a tunnel in the Pennsylvania Mountains that used two-inch-thick.
5 This system can also be supplemented by inserting pressure relief holes into the surrounding soil/rock that provide a path of least resistance for the infiltrating water.Tunnel Maintenance and Rehabilitation Manual of a protective layer on the inside of the membrane. If shotcrete is used a minimum membrane thickness might be required as well as limiting the aggregate size in the shotcrete. which include both preformed sheet materials and liquid applied materials for the waterproofing membrane layer. Figure 4. research of current material technology should be performed prior to selecting the Federal Highway Administration 4-7 . a temperature controlled heat strip can be attached to exposed drainage pipes that prevents freezing of water in pipes and subsequent back up of water. Therefore. It should be noted that material types other than those stated have been used successfully. Additionally. so that adverse hydraulic pressures are not allowed to build up behind the liner. If a fire retardant protective material is applied in sheets then the connection of this material through the membrane must be properly sealed to prevent water infiltration through this joint.
This is recommended as an additional source of information. repair methods discussed in Section B of this chapter should be considered. In the event of a dry crack. Chemical grouts on the other hand can be highly flexible and also have low viscosities that enable them to be injected into very thin cracks. (3) Crack/Joint Injection The most common method for preventing water infiltration in concrete linings is to inject the crack/joint with a particle or chemical grout. 4-8 Federal Transit Administration . It is important to note that if chemical grouts are allowed to dry out they may not be as effective. they are not recommended for any location that might experience structural movements in the future. This could happen if the source of the water infiltration is diverted or the ground water elevation drops below the crack location. and sprayable polymer membranes. their performance in stopping water infiltration is significantly superior to particle grouts. The system chosen may need to be site specific given the possible presence of hydrocarbons or other chemicals that could adversely affect the membrane material. which includes polyethylene and polypropylene. they are used more frequently. The membrane chosen must also be able to withstand any future movement of the structure without reflective cracking and must be resistant to chemical or biological attack from the infiltrating ground water. Since these grouts are nonflexible. it does not specifically describe tunnel applications. The success of this system is primarily dependent on the ability to install a continuous membrane and whether a proper connection of this membrane to the tunnel drainage system is achieved. however. Some of the other materials available include polyolefin.Tunnel Maintenance and Rehabilitation Manual individual components of the waterproofing membrane system. Chemical grouts are expensive. Even with the drawbacks of some chemical grouts. The manufacturer of the materials should be consulted and they should be able to supply material specifications and case histories of where the material might have been used successfully. Committee 515 of the American Concrete Institute (ACI) has also developed a guide for the use of waterproofing membrane systems. an understanding of the chemical properties and their suitability for the desired application is essential. Particle grouts are very fine cementitious grouts that produce nonflexible fillers that prevent water from penetrating the crack/joint. sometimes toxic or flammable and require a high degree of skill for proper application. therefore. therefore.
This type of grout expands into a foam at the presence of water and subsequently seals off the crack.6 shows and explains the procedure for properly injecting a vertical or overhead crack/joint with a chemical grout. It has been found that when applying pressure to inject the grout that low pressure for an extended period is better than high pressure for a short period. Figure 4. not allowing water to pass through. The esters will also not dry out as can occur with polyurethane grouts as described earlier. but often times other methods of repair are more effective for masonry over the long term. The esters have an advantage over the polyurethanes in that they form a gel upon reaction with the water and serve as a barrier to water penetrating a crack. acrylate esters are also being used to inject cracks. a site specific investigation will need to be conducted to determine which material is most cost-effective over the long term.Tunnel Maintenance and Rehabilitation Manual Of the chemical grouts developed to date. therefore it can expand when and if a crack/joint continues to open further. the polyurethane. For this reason. This foam is also moderately resistant to tensile forces. It should be noted that cracks in masonry liners can also be injected. The latter can result in further damage to the concrete. reactive grouts have performed the best for tunnel applications. These methods will be discussed in Section C of this chapter. In addition to polyurethane chemical grouts. Federal Highway Administration 4-9 .
6 4-10 Federal Transit Administration .Tunnel Maintenance and Rehabilitation Manual Figure 4.
The goal of this method is to provide a protective barrier on the outside of the tunnel lining either in specific crack/joint locations or over an entire segment of the tunnel. The material that is injected can form this protective barrier or the injected material can introduce cohesion into the soil. which makes the soil itself impermeable. In the case of a steel or cast iron liner. Some of the available grouts are: • Microfine cement grouts • Polyurethane chemical grouts • Acrylate ester resin chemical grouts • Acrylamide-based chemical grouts (highly toxic). Then. since the liner would not have been designed to handle additional holes being drilled through it. but can force the water along the path of least resistance towards another crack/ joint).Tunnel Maintenance and Rehabilitation Manual (4) Soil/Rock Grouting (Back-Wall Grouting) As an alternative to injecting a crack/joint (which is generally successful for stopping the leak through the injected crack/joint. the existing grout plug holes should be used as the location for the new grout placement. Typically the chemical grouts are more expensive. a grout is injected into the soil/rock and maintained at a constant pressure for a prescribed amount of time to allow the grout to penetrate small cracks in the soil/rock.75 m (2 ft to 2-1⁄2 ft) center-to-center spacing for their injection pattern. There are different grouts that are available and a site-specific investigation is necessary to determine which one is best suited for the particular conditions.6 m to . the cement grouts can be used for areas where voids exist behind the liner and large volumes of grout are required. similar materials can be injected through the liner into the soil/rock beyond. Another example of this system being used successfully would be in the subway tunnels of the Toronto Transit Commission Federal Highway Administration 4-11 . To date. One example of this system would be the Bay Parkway Bridge in New York City which is 45 m (150 ft) wide and has soil cover over a rail line running underneath that essentially forms a tunnel. this repair has performed well and other similar applications are being considered. The procedure for this method consists of drilling holes perpendicular to and through the liner on a predetermined pattern (based on ground conditions and amount of water present). The New York City Department of Transportation chose to utilize the acrylate ester resin chemical grout as the injection material and they used a . and installing mechanical injection packers. therefore.
(6) Segmental Joint Repair Segmental liners can be made of either precast concrete. It should be noted that this system could be used in conjunction with other systems. which enables the infiltrating water to be collected from the exterior side of the pipe and exported into the tunnel drainage system at the bottom of the crack. An example would be to back-wall grout a particular area and therefore force water to flow to a predetermined point where a drainage system could be installed. 4-12 Federal Transit Administration . As with the other repair techniques. This is especially true for this method due to the possible weakening of the structural capacity of the lining depending on where and what direction the crack is located. a registered professional engineer should review and approve the application of this method to the specific site location.9 deal specifically with cracks and joints respectively and begin by routing or cleaning in the case of a joint. For their situation they chose to use an acrylamide based chemical grout and they had specialty grouting work cars fabricated to condense and mobilize the operation for brief nighttime work periods when the tunnel could be closed. More details for installing drains within the liner are given in the next method.8 and 4. steel. Figures 4. Figure 4. Their experience has shown that this can be a reliable method of stopping water infiltration. then another approach is to convert a crack into a joint that allows differential movement of the concrete. The difference with this method is the addition of a semi-perforated pipe that is inserted into the crack/joint.7 portrays a method of routing out the crack or joint to a specific depth and then properly sealing off the water infiltration with successive layers of different impervious materials. or in the case of older tunnels–cast iron. mastic. Water infiltration generally occurs at the joint location where the original lead. The pipe can be covered with a neoprene rubber sheet (liquid neoprene is also applicable) on the exterior of the concrete or mastic and impervious mortar can be used to make the repair look just like a normal joint.Tunnel Maintenance and Rehabilitation Manual (TTC). The finished product will look and behave like a joint in that it will allow for some differential movement and will be watertight. and add waterproofing components to the existing joints. or rubber seal has failed. (5) Crack/Joint Repair If water infiltration through cracks/joints in concrete linings cannot be stopped by injecting the crack/joint as described previously because of excessive movement which surpasses the tensile strength of the grout material used.
Cracks and joints can also be injected with particle or chemical grouts as discussed previously. the cracks are injected similar to method (3). for single-pass liner systems with any of the three segmental liner types. In addition.Tunnel Maintenance and Rehabilitation Manual This can be corrected by repacking the joint with new sealing material and installing new gaskets at boltholes. Federal Highway Administration 4-13 . the processes described in method (4) can be implemented on the exterior of the liner with the precautions noted. In the case of precast concrete segments.
7 4-14 Federal Transit Administration .Tunnel Maintenance and Rehabilitation Manual Figure 4.
8 Federal Highway Administration 4-15 .Tunnel Maintenance and Rehabilitation Manual Figure 4.
9 4-16 Federal Transit Administration .Tunnel Maintenance and Rehabilitation Manual Figure 4.
especially in masonry. with some modifications. should an extensive repair be needed. it is recommended that a specialized consultant be obtained to develop possible solutions that are specific to the tunnel in question. latex/acrylic-modified. although many of these are complex in nature. Furthermore. This method has some drawbacks that include decreasing the tunnel clearances and trapping the moisture inside the original liner. There are several relatively new technologies that are being used for new tunnel construction that can also be incorporated into reconstruction procedures. A few of the general material classifications for shotcrete are–cementitious. replace it with a structural layer of shotcrete. then place a geotextile layer and waterproofing membrane (either sheet membrane or sprayable polymer membrane). The latter method is less common because the drains can become clogged with fine soil particles. Another more in-depth procedure is to remove all or portions of the existing liner. or twocomponent epoxy. and finally provide a protective.Tunnel Maintenance and Rehabilitation Manual c) Reconstruction and New Construction If the tunnel degradation has advanced to a point where repairing numerous localized areas of the liner becomes cost prohibitive. (1) Shotcrete Applications The use of shotcrete in tunnel construction has greatly increased since the advent of the Sequential Excavation Method (SEM) and the improvement of the shotcrete materials and application processes used. In addition. There are various detailed techniques that will only be explained briefly. This could include shotcrete or pumping plasticized concrete within a form liner. Trapped moisture can lead to deterioration due to chemical reactions between the water and the liner material. These methods generally attempt to prohibit the water from infiltrating the final liner and thus entering into the tunnel space. This is accomplished by collecting the water and draining it away either within the liner or on the exterior of the tunnel. using an exterior drainage system in a tunnel below the ground water elevation is normally not effective over the long term because of the ability for water to penetrate very small cracks that develop between drains. As mentioned previously. the membrane thickness and shotcrete aggregate size may have restrictions placed on them in order to ensure that the membrane is not damaged Federal Highway Administration 4-17 . Shotcrete can also be used in tunnel rehabilitation in various forms. The following paragraphs describe available systems for extensive lining reconstruction or that are also applicable for new tunnel construction. non-structural finish liner of shotcrete on the inside that initially adheres to the waterproofing membrane during curing. it may be necessary to reconstruct larger areas using different techniques. One method is to simply coat the entire interior of the tunnel walls and ceiling with a mix design that makes the cured shotcrete relatively impervious to water.
It is recommended that a detailed site investigation be performed to determine if this final lining will need to resist any hydrostatic loadings. concrete or rock.Tunnel Maintenance and Rehabilitation Manual during the shotcreting procedure. 4-18 Federal Transit Administration . a modern laser-controlled cutterhead mounted on a boom as shown in Figure 4. It is possible to place another geotextile layer or other protective material on the inside of the membrane. Also. Once the crack occurs. the joints can be fitted with a new system that allows the joint to be initially injected with chemical or particle grouts and to be reinjected at any future time that the joint might begin to leak due to settlement of the structure. the product can be injected with a chemical or particle grout to stop water infiltration. This method allows water that penetrates the initial liner to be directed down the tunnel along the waterproofing membrane to the primary tunnel drainage system. The existing liner can be removed with traditional demolition techniques or. However. Section A.10 can be used to remove precise depths of masonry. but attachment of this layer is difficult since the attachment mechanism has to puncture the membrane The thickness of this liner is dependent on the tunnel size and shape and the amount of water infiltration that is expected. Part 3b(5). when there is a complete tunnel reconstruction or new tunnel construction. It is not often that there is an opportunity to completely reconstruct a joint in an existing tunnel.10 – Laser controlled cutter for removing portions of existing tunnel liner. (Photo courtesy of Tunnels & Tunnelling North America) (2) Joint Control Deteriorated joints can be repaired as described previously in Chapter 4. products exist that can be inserted at anticipated crack locations that actually facilitate crack development atthat location. Figure 4. depending on the depth of removal desired.
• Federal Highway Administration 4-19 . The defect must first be evaluated to determine the cause and the severity of the deterioration. Cracks may have existed previously that permit deleterious elements access to the reinforcement steel. signs of this problem are delamination (a separation of the concrete from the embedded• steel). Concrete deterioration in tunnels may be caused by any of the various factors listed below. whether water infiltration is the cause. chemicals. and the structural impact of the defect. a repair analysis will need to account for the replacement or repair of the finish as well. location of the repair to be completed. Other considerations include the use of water reducing and shrinkage reducing admixtures. surface spalling. Factors affecting the repair are the severity to which the concrete has deteriorated. CONCRETE REPAIRS As concrete deteriorates. chlorides. Therefore. Repairs should not be made until the cause of the defect has been determined and the situation remedied. When major repairs or reconstruction is required. in order to select the best repair method.Tunnel Maintenance and Rehabilitation Manual (3) Concrete Design One of the most effective methods of preventing water infiltration in reconstruction or new construction is to properly design the concrete or shotcrete mix to approach impermeability and to not be as susceptible to cracking. The repairs included in this manual are commonly used and have been performed in various tunnel locations. or cracking. Another admixture that is increasing in usage is a waterproofing additive. such as oxygen. capable of being performed quickly during non-operating hours. This is primarily done by ensuring adequate reinforcement and limiting the water/cement ratio to 0. It should be noted that many concrete linings in highway tunnels have an additional tunnel finish that covers the concrete and therefore may hide the extent of the deterioration.45. Corrosion From Embedded Metal – Several factors contribute to accelerate the corrosion of embedded steel. easy to install. it is important that proper repairs be made to avoid further degradation of the structure. The repairs must be durable. stray electrical currents. • Water Infiltration – Refer to Chapter 4. and cost-effective. or the same problem may repeat itself in the newly repaired concrete. Once the corrosion has begun. B. This finish commonly is porcelain tile or prefabricated metal or concrete panels. Section A for a discussion of the negative effects of water infiltration and suggested methods of repair. water. This admixture reacts with the fresh concrete to produce crystalline formations throughout the cured concrete that resist the penetration of water. a detailed site-specific investigation should be undertaken to determine what methods and materials can be applied based on current research and experience. and low pH (acidity).
around the injection ports to contain the resin that fills the crack. if the concrete is permitted to segregate when placing. one of the following potential repairs should be implemented: 1. This reaction produces a water-soluble calcium compound. For cracks that are void of water. and salt solutions are common enemies of concrete. However.11). This expansion and contraction can lead to cracking. to prevent the resin from running completely through the crack. see Chapter 4 Section A for methods of repair. For cracks on a horizontal surface. Crack The most common defect found in concrete is a crack. 4-20 Federal Transit Administration . • Thermal Effects – Thermal loads cause the concrete to expand and contract putting undue stress on the concrete. Once there. and movements are not expected. • • Once the defect has been evaluated and the cause determined. due to the relatively uniform environment within a tunnel. the water freezes. the crack can be filled with an epoxy resin.Tunnel Maintenance and Rehabilitation Manual • Disintegration of Material – Certain chemicals like acids. cracks may develop over the underlying steel support on the slab topside. then expands and exerts tension forces on the concrete. Loading Conditions – Load placement will have varying effects on concrete.12 for examples of this repair. Acid attacks concrete by reacting with the calcium hydroxide of the hydrated Portland cement. However. then the strength and long-term durability of the concrete will be affected. if there is insufficient vibration to consolidate the concrete. alkaline solutions. Shear cracks may also develop near the support. For cracks where water infiltration or moisture is present. In the center of the span. For continuous concrete spans in roadway slabs over air ducts. the underside of the concrete surface may need to be sealed. For vertical and overhead cracks. If the reinforcement steel is placed improperly. or if the concrete is not finished or cured properly.11 and 4. cracks will develop on the underside of the slab. Porous concrete will absorb water into small capillaries and pores. if it is accessible. a paste gel is placed on the surface of the crack. Poor Workmanship – Workmanship is critical to overall concrete performance. this form of degradation of the concrete is limited to areas near portals and possibly within air plenums where temperature fluctuations are more likely. the crack may be gravity filled with epoxy by constructing a temporary dam (see Figure 4. Near the surface small flakes of concrete will break away causing further exposure and eventual spalling and removal of aggregate with the process continuing inward. which is then leached away. See Figures 4.
11 Federal Highway Administration 4-21 .Tunnel Maintenance and Rehabilitation Manual Figure 4.
Tunnel Maintenance and Rehabilitation Manual Figure 4.12 4-22 Federal Transit Administration .
It is caused by the separation and removal of a portion of the surface concrete. Coat the reinforcement steel and the concrete surface with an anti-corrosion coating. whereas deep spalls penetrate 50 mm (2 in) or more into the concrete and usually expose the reinforcement steel within. However. or if the spall extends behind the reinforcement steel. If the inspector recommends that the spalls should be repaired to preserve the integrity of the concrete. Depths of spalls vary and for repair purposes can be classified as either shallow or deep. to the surface. Clean the reinforcement steel of any corrosion. then this repair method can be used. then the methods and materials given in this section may not be adequate to resist the effects of future infiltration. Clean the concrete surface of deleterious materials. If.13) This repair is typically performed for aesthetic reasons and not necessarily for structural integrity of the lining. But. Sawcut around the spalled area on a 20-degree angle. Spall A spall is an irregular shaped depression in the concrete in which the fracture is parallel. resulting in a pop off of the concrete cover. If corrosion is due to water infiltration from the exterior of the tunnel. the following procedures may be utilized: a) Shallow Spall With No Reinforcement Steel Exposed (See Figure 4. it is recommended that the extent of the corrosion be determined and the spall be repaired by the method given in Part c). some spalls may occur that do not have any exposed steel.14) If the exposed reinforcement steel is only slightly corroded with no significant section loss. Reinforcement steel can also be exposed in a shallow spall if it was originally placed too close to the surface of the concrete. For this situation. Place polymer repair mortar in the spall to original concrete depth. Suggested steps include: • • • • b) Remove all loose or delaminated concrete on the spall surface. it is necessary to address the water infiltration using methods given in Chapter 4. Special attention needs to be given to determining the cause of any corrosion on the reinforcement steel. typically due to corroded reinforcement steel. Federal Highway Administration 4-23 . where the tensile stresses in the concrete exceed the tensile capacity.Tunnel Maintenance and Rehabilitation Manual 2. Suggested repair steps include: • • • Remove all loose or delaminated concrete around the exposed reinforcement steel. however. if a complete restoration of the original concrete surface is desired. the corrosion appears to be deeper than the current spall depth. Section A. A shallow spall typically penetrates less than 50 mm (2 in) into the concrete. the following methods can be used. Shallow Spall With Reinforcement Steel Exposed (See Figure 4. or slightly inclined.
Tunnel Maintenance and Rehabilitation Manual Figure 4.13 4-24 Federal Transit Administration .
14 Federal Highway Administration 4-25 .Tunnel Maintenance and Rehabilitation Manual Figure 4.
then. given that a proper bonding agent is used.15 and 4. perform sawcut as described in Part a) and place polymer repair mortar as final step. Make sure that anti-corrosion coating and polymer repair mortar are chemically compatible. The extent of this corrosion should be determined and the concrete should be removed around the effected reinforcement steel to a width of a least one half the existing reinforcement steel spacing and to a depth of at least 25 mm (1 in) behind the back of the reinforcement steel. Deep Spall With Reinforcement Steel Exposed (See Figures 4. manual application is often not performed correctly and insufficient coverage is obtained. Clean the concrete and steel surfaces of deleterious materials. prior to application of anti-corrosion coating. Place polymer repair mortar in the spalled area unless the area is very large such that the use of shotcrete or plasticized concrete pumped with a form is more costeffective. any exposed reinforcement steel in a deep spall will be corroded. that depth can be reduced to 6 mm (1⁄4 in).Tunnel Maintenance and Rehabilitation Manual • If replacing the spalled concrete is recommended. 4-26 Federal Transit Administration . experience has shown that separate. Provide new reinforcement steel where necessary and overlap with existing steel according to current American Concrete Institute (ACI) standards. It is recommended that the sawcut around the perimeter of the spalled area be at least 25 mm (1 in) deep to accommodate a repair material with aggregate.16) c) Generally. Therefore. If the material being used does not include aggregate. Where shotcrete is used. Specific repair recommendations are as follows: • • • • • • Remove all loose or delaminated concrete from the spalled surface and face of the reinforcement steel. As for bonding agents. Sawcut around the spalled area. Coat the reinforcement steel with an anti-corrosion coating. a bonding agent admixture can be substituted for a certain percentage of the water in the mix. additional welded wire fabric is recommended to help support the shotcrete.
15 Federal Highway Administration 4-27 .Tunnel Maintenance and Rehabilitation Manual Figure 4.
16 4-28 Federal Transit Administration .Tunnel Maintenance and Rehabilitation Manual Figure 4.
polyaramide glass fiber sheet products. and ability to obtain a smooth surface for the final tunnel finish (tile. These effects could be due to water infiltration. the CIP concrete liner is covered with a reflective material such as tile or metal panels. An epoxy coating is applied to the concrete surface and the fiber sheets are installed in two layers. This method is performed by first completing crack and spall repairs. Particular attention should be directed to determining if structural components need to be temporarily shored so that the component to be repaired is unloaded. crack injection. and then the concrete surface is prepared as per the manufacturer’s instructions. therefore. or membrane application should be performed prior to actual concrete repair. they may also have extensive repair needs to remedy cracking. etc. is that a registered professional engineer should evaluate and approve suggested repairs and methods used. Other materials with cellular structures can be used for active cracks. LINER REPAIRS A general note that applies to all the liner repairs suggested in the following sections. If actively moving cracks are epoxy grouted. Sections A and B. If dry cracks need structural repair. age. cost. soil grouting.) application. the repair technique must take into account the attachment requirements of the final tunnel finish. durability and resistance to corrosion (if designed and constructed properly). • Oftentimes in highway tunnels. spalling. Cast-in-Place (CIP) Concrete CIP concrete liners are common in both highway and transit tunnels because of strength. epoxy resins can be injected. • • If water infiltration is occurring. Another retrofit method that is being used more often for strengthening concrete tunnel linings is carbon fiber. Spall repair is dependent on the size and depth of the spall and can be repaired with a polymer mortar for smaller spalls or with a plasticized concrete or shotcrete for larger spalls. metal panels. or unforeseen changes in ground conditions surrounding the tunnel. Care must be given to cleaning or replacing exposed steel that has experienced corrosion and section loss. then methods of water redirection. inadequate design/construction. Although there are many benefits for using CIP concrete liners. 1. then subsequent cracks adjacent to original crack may occur depending on the elastic capacity of the epoxy material. adaptability to site conditions. the sheets with fibers in Federal Highway Administration 4-29 . and reinforcement steel deterioration.Tunnel Maintenance and Rehabilitation Manual C. but a determination must be made if there are active movements at the crack. but will briefly be reiterated below for reference. The methods for repair of CIP concrete liners are the same as those given for general concrete in Chapter 4.
Also. and speed of erection. Repair of precast segmental concrete liners is often related to degradation of the joints. the joints can be injected with grout to help seal them off to water. The sheets are impregnated with epoxy. Precast Concrete Precast concrete liners are often used as a primary liner that is placed by the TBM or manually within the shield of a driven tunnel. Section A or B depending on whether water infiltration is present. transit tunnels. therefore repairs are made to the precast directly. the method of repairing a joint consists of repacking the joint with new gasket material and replacing any bolts that have lost their structural capacity. 3. Other defects such as cracks and spalls that can occur within a precast panel can be repaired using the same methods given in either Chapter 4. the precast concrete liners are often covered with an interior cast-in-place concrete liner for supporting the tunnel finish as described previously. this method is not recommended in areas of the tunnel that might experience water infiltration. Caution: This method should not be used in areas where fires or excessive heat may occur. subsequently subjecting it to corrosion effects as well. They are used because of their easy adaptability to site conditions. especially in tunnels subject to water infiltration. 2. In the event of a fire. Steel Within a tunnel. structural steel is used for two main purposes: as segmental steel liners and as structural columns or beams. therefore a routine inspection is crucial. these materials will fail and therefore the concrete lining will lose any structural improvements provided by the carbon fiber sheets. due to the possible flammability and toxicity of the materials used. Also. Structural columns and beams are mostly found in transit tunnels although steel beams are also used in structural slabs for support of roadway or overlying buildings and tunnels. which can expose the reinforcement steel. As mentioned previously in the water infiltration section. As with structural steel in other uses 4-30 Federal Transit Administration . Obviously. The joint material can fail and corrosion of the bolts can lead to spalling of the concrete. this will also help to prevent further cracking and exfoliation of the concrete lining. the ideal is to repair the joint before the corrosion becomes too extensive. Generally precast segmental liners are bolted together to compress gaskets in the joints to prevent water infiltration and to provide overall structural stability to the liner. Conversely. which do not have the same visibility constraints. This type of retrofit can be used to increase the load capacity of the tunnel arch when there is increase in the weight of overburden.Tunnel Maintenance and Rehabilitation Manual the transverse (circumferential) direction are installed first followed by sheets with fibers in the longitudinal direction. In highway tunnels. sometimes use a single precast concrete liner with no interior finish.
Table 4. If clearance is adequate. Research should be conducted to determine the best paint type for the given situation.1 illustrates the changes in steel weldability over time. if there is any doubt. Traditionally. then new joint material must be installed along with new bolts. then the steel should be tested according to American Welding Society (AWS) standards. If stray current is suspected. or channels have significant section loss (greater than 20 percent). One general note is that for older structures the weldability of the steel must be determined due to the wider range of chemical composition allowed in their fabrication. Table 4. For steel segmental liners that have section loss or considerable corrosion of the panels. Typically this will be done during the inspection process and will be recorded for reference in determining the type of repair. or from defects in the material. headed studs may be welded to the liner and then a layer of reinforced concrete or shotcrete can be constructed inside the steel liner. It is also possible for steel to develop cracks due to improper design/erection.Tunnel Maintenance and Rehabilitation Manual such as bridges and buildings. Painting the steel is the best method for preventing corrosion. But. Prior to painting. epoxy paints have performed well for steel. then install an insulating sleeve over the bolt to prevent current from passing between dissimilar metals. threaded rods that anchor the re-bars may replace steel bolts that connect the liner segments. it is necessary to determine the cause and actual extent of the damage. • • • • Federal Highway Administration 4-31 .1 – Weldability of Steel If the existing steel utilizes welded connections. then plates can be welded on the interior surface to replace the area of section loss. then it is safe to assume that the steel is weldable. the primary method of failure is by corrosion caused by moisture. If welding is not practical. Below are examples of repair procedures that can be used for steel defects: • If beams or columns made from W-shapes. If liner joints and bolts are corroded. fatigue. T-shapes. then consider welding or bolting plates to flanges or webs to increase the capacity in the area of the section loss. existing steel should be blast cleaned of all present corrosion – down to white metal. To repair these defects. which in transit tunnels can be enhanced by the presence of stray current from the rail electrification system.
Currently. Generally cast iron is far less ductile than steel and therefore brittle failure and cracking can be more common. nodular.) and the accessibility of the item to be repaired. a) Bolting It is possible to bolt new cast iron members over existing cracks. Therefore. a watertight connection must be accomplished. which is difficult since the cast iron components in a tunnel are not usually removable. this method is 4-32 Federal Transit Administration . then the joint itself could be made watertight by inserting gasket material or by injecting the joint with a chemical grout. When doing so. such as the primary tunnel liner segments and columns (usually tubular) in open areas of transit tunnels. then a waterproofing material will need to be applied between the new piece and the existing lining. a layer of reinforced concrete or shotcrete can be added inside the cast iron liner. However.17 – 4.19. other methods of repair will usually be recommended. that this method be investigated. Cast iron differs from steel in that it is not as susceptible to corrosion. etc. or areas of corrosion. there are some general comments that can be made about repair methods that can be used. so replacing bolts or rivets that connect the liner segments with threaded rods to anchor the re-bar is suggested. d) Metal Stitching Technology does exist to stitch the cast iron in a manner illustrated in Figures 4. If the repair is at a joint between liner segments. Cast Iron Cast iron is similar to steel in the extent of its use for tunnel construction. If the repair is the addition of a plate over a crack or area of section loss in the panel.Tunnel Maintenance and Rehabilitation Manual 4. Repair of cast iron defects is much more difficult than for steel and therefore a detailed. b) Welding In general cast iron that is used in tunnels should not be considered weldable. site-specific investigation is required to determine the proper method for repair. some welding techniques can be attempted. if clearance is adequate. It is recommended that if the cast iron cannot be repaired using other methods. malleable. c) Concrete Liner Similarly to steel liners. Depending on the type of cast iron (gray. However as mentioned above welding is not usually an option. Significant expertise is required and preheating is necessary. white.
Figure 4.18 – Metal Stitching Procedure – (Figure courtesy of Lock-N-Stitch Inc. which demonstrate that the method provides a high strength.17 – Metal Stitching Detail – (Figure courtesy of Lock-N-Stitch Inc. compressors and pipes. hardening and additional cracking because heat is not used in the repair process.Tunnel Maintenance and Rehabilitation Manual being used with much success on high-pressure castings such as water pumps. valves. This process can restore the original strength to the casting without the problems associated with on-site welding such as stress. watertight repair.) Federal Highway Administration 4-33 .) Figure 4. distortion.
19 – Metal Stitching Completed – (Photo courtesy of Lock-N-Stitch Inc.Tunnel Maintenance and Rehabilitation Manual Figure 4.) 4-34 Federal Transit Administration .
the ground water was and remains very effective. Masonry liners that are still in existence today range from very good condition to very poor condition. Shotcrete can be used to cover and protect a waterproofing liner or as a repair liner for tunnel rehabilitation. Section A and B. which formed a drainage channel for ground water. More recently with the addition of steel or synthetic fibers and fine-aggregates.Tunnel Maintenance and Rehabilitation Manual 5. Primarily it is used as a primary support liner for the excavation prior to the construction of the final liner. Federal Highway Administration 4-35 . If they were constructed within geologic conditions that kept them relatively free from the presence of ground water. This is proven by the fact that most of the world’s historic tunnel structures were constructed with masonry and still exist today. or wire mesh for additional strength. which can achieve significant strength in thin. cured shotcrete will behave similarly to standard cast-in-place concrete and will be susceptible to cracking. If repairs need to be made to shotcrete liners. Masonry The term “masonry” refers to materials such as stone or brick that are connected together in the field with mortar. or draining of. There are various uses for shotcrete in tunnel construction and each use may require a different mix design and application method. smooth layers. Another terminology that is sometimes used is “gunite. The original waterproofing system typically consisted of a timber primary support lining and void space between the timber and masonry that was filled with tunnel debris. In older tunnels–generally those built in the 19th century–masonry was the construction material that was most readily available and economically possible for construction of the liners. Oftentimes. they can be performed in the same manner as the methods given in Chapter 4. lattice girders. spalling and delamination. even after concrete and steel began to be used as construction materials for cut-and-cover tunnels. the timber lining rots and the water erodes the material that filled the void. depending on whether water is present at the defect. Shotcrete Shotcrete is a material that is gaining increasing usage for tunnel construction as materials and methods of application continually improve. Another reason that masonry tunnel liners remain in good condition is that the original method for waterproofing against. Over time. This procedure can be supplemented with rock bolts. causing the masonry itself to be exposed to the water. depending on the severity of any ground water presence. 6.” which refers to fine-aggregate shotcrete. Generally. which in the case of brick tunnel liners could be five or more courses thick. shotcrete has been able to be used as a final liner. even though the mix designs were intended to reduce those effects. masonry was still used as a protective liner for the mastic waterproofing that was used on the outside of the finished lining. the masonry itself could last without much attention for a very long time.
For the latter situation. Inject cracks with chemical or particle grouts (take care to use grouts that are suited for the moisture content present in the crack). Apply a shotcrete lining if vertical and horizontal clearances can be reduced. This practice is discouraged because any moisture or water that enters the masonry will be trapped and cause swelling. Part 3(b)(4). thus endangering the tunnel occupants. or pipe network will most likely need to be installed at the location of the leak to divert the water towards the tunnel drainage system. Exposed Rock Many older tunnels that were constructed through dry. These tunnels may function without need for repair long into the future. If the problem is caused by extensive water infiltration. Provide horizontal reinforcement steel embedded in the joint across the crack prior to repointing. If it is determined that repairs are needed. then methods given in Chapter 4. Repoint mortar by removing existing mortar to depth of twice the joint thickness or 18 mm (3⁄4 in) minimum and replacing with new mortar of equal strength and color but increased water impermeability. some type of waterproofing liner. One repair that is not recommended is to apply an impermeable coating–such as a paint or epoxy–to the interior surface of the masonry. underlying causes of cracks and water infiltration must be addressed first. were left unlined except for zones near the portals or where the rock was incompetent to carry the loads. but it is more likely that ground movements will either cause pieces of rock to fracture and fall to the invert. 4-36 Federal Transit Administration . Section A should be considered. then the actual cause of the deficiency needs to be determined in order to select the proper repair method. Replace cracked or brittle masonry units in localized areas. in conjunction with possible ground collapse in the space behind the brick lining. 7. sound rock conditions. However. membrane. If waterproofing is needed. otherwise the following are suggested: • • • • • • Inject cementitious grout into known large voids behind liner to stabilize ground material. use methods described in Chapter 4. it and the mortar can swell and become brittle depending on the firing temperature of the brick and the chemical make up of the mortar. or they will open up cracks in which water will eventually infiltrate into the tunnel space. Section A. for added strength. inevitably the face of the masonry will delaminate and fall off. can induce stresses into the lining that cannot be resisted and therefore.Tunnel Maintenance and Rehabilitation Manual When masonry is exposed to water. This. structural cracking occurs. which further exacerbates the water infiltration problem.
cable bolts. but can be anchored mechanically for short-term applications. then there are methods that can be used to structurally support the exposed rock. However. They can sometimes be prestressed. Rock bolts can be used to secure thicker sections of fractured rock to a competent layer behind.Tunnel Maintenance and Rehabilitation Manual If water infiltration is not a concern. Listed below and shown in Figure 4.20 – Rock Bolt Types Federal Highway Administration 4-37 . To completely protect against falling debris and to increase the structural capacity of the liner. so that it does not pose a threat to the tunnel occupants. this process does reduce the interior clearances. Examples of rock bolts are standard rock bolts.17 are some examples of those methods: • • Metal plates attached with short anchor bolts can be used to support surface defects. or friction bolts (dowels). they are normally grouted into the drilled hole using chemical or particle grouts. wire mesh (chain link) can be attached to the surface using rock bolts. but normally the stress is induced during future ground movements. To protect from small spalls or pieces of fractured rock. Also. shotcrete or a thin cast-in-place liner can be installed. The plates can vary in width and length as needed to cover fractured rock. • • Figure 4.
Tunnel Maintenance and Rehabilitation Manual 4-38 Federal Transit Administration .
price of equipment. The life cycle costs of a given alternative include all associated costs over the expected life of the option. tunnel may need shut down for repair. therefore.g. There are two main methods for performing a life cycle cost analysis. certain type of light bulbs may need to be replaced every five years). this method attempts to bring all of the present and future costs of a given option to present day values. the present worth and the annualized methods. Rehabilitation costs – Future expense for known procedure at specified time (e. Operating/energy costs – Annualized amount to operate (e. 1. An example of a future expense would be the rehabilitation costs mentioned above. User costs – Costs associated with impact on the functioning of tunnel (e. construction costs. etc. impact to traffic can be shown by applying an annualized cost to each hour tunnel is closed). Maintenance costs – Annualized costs to maintain equipment or repair minor defects.Tunnel Maintenance and Rehabilitation Manual APPENDIX A: LIFE-CYCLE COST METHODOLOGY To properly plan for future repairs or scheduled maintenance in a tunnel. Present Worth Method As the name implies.g. In general these costs may include: • • • • • • Initial costs – Engineering or design costs.g. This process involves evaluating the alternatives over a given duration or economic life to determine specific costs involved for each option and then equating them through a series of mathematical formulas that enable the costs of each option to be compared at a common point in time. The general form of the equation for determining the present worth of a future expense is: Federal Highway Administration A-1 . mechanical fan or railroad tie may be of some value to others even after it has served its purpose in the tunnel).g. it is beneficial to perform a life cycle cost analysis of the different options involved for each anticipated major repair to ensure the greatest cost efficiency over the life of the tunnel. The present worth of the future expense is also the amount that could be invested today with reinvested interest over the duration to equal the amount of the future expense. Determining the present worth of a future expense is done by taking into account inflation of the dollar and therefore discounting the amount by a predetermined rate over the period between the future expense and the present time. namely. Salvage value – Sale value of equipment at end of expected life (e. cost of electricity to run mechanical equipment). This process should be completed for each major repair/rehabilitation and subsequently the options could be compared.
Tunnel Maintenance and Rehabilitation Manual Where P F n i = = = = Present worth Future one-time expense Number of years Discount rate Future expenses can also be uniform. Annualized Method = = = = Present worth End-of-year payments Number of years Discount rate The annualized method is used to transform present and future costs into a uniform annual expense. Standard economic tables have been developed that give factors that are based on the discount rate and the economic life under consideration. These factors are also unique to the desired result. Where A P n i = = = = End-of-year payments Present worth Number of years Discount rate The above two methods can also be performed without using the actual equations given. in that the same expense occurs at the end of each year. The procedure for using standard economic tables is as follows: A-2 Federal Transit Administration . The general form of the equation for determining the present worth of an endof-year expense is: Where P A n i 2. This annual expense can be compared to the annual expenses of the other repair/rehabilitation alternatives to determine which one is most cost effective. Converting all future expenses into a present value as before and then using the equation below to convert that value into an annual expense will provide a uniform annual cost. An example of this would be the annualized maintenance costs described previously.
since the future costs are discounted in relation to the initial cost. It is suggested that his procedure or something similar be used if the effects of the human factors are of concern during the economic life of the alternatives. but as can be expected. Develop a cash flow diagram for each option.Tunnel Maintenance and Rehabilitation Manual • Determine the discount rate (i) and economic life (n) to be used for the analysis. A low discount rate favors high initial cost alternatives since future costs are added in at almost face value.n) – or end-of-year payments (A) given present worth (P) at discount rate (i) for number of years (n). a difference in discount rate can actually change the final outcome of the analysis if the repair/rehabilitation options being considered have different arrangements of uniform and onetime costs. whether uniform or one-time.i%. Because of the power of compounded interest. In his book entitled Value Engineering: Practical Applications … for Design. Where alternative strategies have similar maintenance. and insert them in the proper formula given below along with the factor from the appropriate economic table. (P/A. • • Caution must be used in determining the appropriate discount rate.i%. and safety along with the economic costs. has developed a procedure for weighted evaluation of human factors such as comfort. and operating costs. the discount rate will have a minor effect on the analysis and initial costs will have a larger effect. Construction.n) – or present worth (P) given future expense (F) at discount rate (i) for number of years (n). (A/P.E. performance. High discount rates favor alternatives that stretch out costs over a period of time. Alphonse Dell’Isola. In the case of a discount rate equal to 0. Take individual costs. P. the annualized method must be used.i%. Federal Highway Administration A-3 . all costs are treated equally regardless of when they occur. Maintenance & Operations. rehabilitation. Otherwise. which shows all relevant costs described above on a timeline of years in the economic life.. (P/F. Therefore further comparison can sometimes be utilized to take into account the “human factors” of the alternatives. a draft report for FHWA: “The discount rate can affect the outcome of a life cycle cost analysis in that certain alternatives may be favored by higher or lower discount rates.” The above procedures will allow the most economical repair/rehabilitation alternative to be identified. appearance. According to Peter Kleskovic who wrote A Discussion of Discount Rates for Economic Analysis of Pavements. It is important to choose an economic life that is equal for the given alternatives if the present worth method is to be used. the least costly is not always the best.n) – or present worth (P) given end-of-year payments (A) at discount rate (i) for number of years (n).
..... Estimated Life............................................. Replacement Ties (years 12 and 24) .............................000 $20................... Consider a transit tunnel in which the track support system is in need of replacement........................Tunnel Maintenance and Rehabilitation Manual 3..................................... 30 and 40) ........50 years b) Ballasted Track: Initial Construction Costs ....................................................................000) Estimated Life........................000 ($50........................................................................ a) Direct Fixation Slab Track: Initial Construction Costs .... Currently the system is ballasted track and can either be replaced with direct fixation slab track or a new..............................000 Joint/Crack Sealing (years 10..... ballasted track system..... Annual Maintenance ....................... $500..............000 Annual Maintenance .......... ($100........... Salvage.. Costs given to the different options are shown below for every 150 m (500 ft) of track.............................................. $250. $20............................ 20........................000 $200..... $1............................000) 35 years A-4 Federal Transit Administration ... Example The following example uses completely arbitrary costs to properly show the benefits of a life cycle cost analysis........................000 Salvage........
Factors from Standard Economic Table (assume 7 percent discount rate)
n 10 12 20 24 30 35 40 50 (P/F) 0.5083 0.4440 0.2584 0.1971 0.1314 0.0937 0.0668 0.0339 (P/A) 7.0236 7.9427 10.5940 11.4693 12.4090 12.9477 13.3317 13.8007 (A/P) 0.1424 0.1259 0.0944 0.0872 0.0806 0.0772 0.0750 0.0725
Alternate 1 – Direct Fixation Slab Track (1) Present Worth Method P = $500,000 + $1,000(P/A,7%,50) + $20,000(P/F,7%,10) + $20,000(P/F,7%,20) + $20,000(P/F,7%,30) + $20,000(P/ F,7%,40) – $100,000(P/F,7%,50) P = $500,000 + $1,000(13.8007) + $20,000(0.5083) + $20,000(0.2584) + $20,000(0.1314) + $20,000(0.0668) – $100,000(0.0339) P = $529,709 (2) Annualized Method A = $500,000(A/P,7%,50) + $1,000 + $20,000(P/F,7%,10)(A/P,7%,50) + $20,000(P/F,7%,20)(A/P,7%,50) + $20,000(P/F,7%,30)(A/P,7%,50) + $20,000(P/F,7%,40)(A/P,7%,50) – $100,000(P/F,7%,50)(A/P,7%,50) A = $500,000(0.0725) + $1,000 + $20,000(0.5083)(0.0725) + $20,000(0.2584)(0.0725) + $20,000(0.1314)(0.0725) + $20,000(0.0668)(0.0725) – $100,000(0.0339)(0.0725) A = $38,403/year
Alternate 2 – Ballasted Track (1) Present Worth Method P = $250,000 + $20,000(P/A,7%,35) + $200,000(P/F,7%,12) + $200,000(P/F,7%,24) – $50,000(P/F,7%,35) P = $250,000 + $20,000(12.9477) + $200,000(0.444) + $200,000(0.1971) – $50,000(0.0937) P = $631,689 (2) Annualized Method A = $250,000(A/P,7%,35) + $20,000 + $200,000(P/F,7%,12)(A/P,7%,35) + $200,000(P/F,7%,24)(A/P,7%,35) – $50,000(P/F,7%,35)(A/P,7%,35) A = $250,000(0.0772) + $20,000 + $200,000(0.444)(0.0772) + $200,000(0.1971)(0.0772) – $50,000(0.0937)(0.0772) A = $48,837/year
Since this example used two different time periods the present worth results are not useful in comparing costs, but the annualized method is since the outcome is a cost per year. From this example it can be seen that even though Alternative 2 had a lower initial cost, it turned out to be more expensive over the long term due to greater costs to repair and maintain that alternative. This process can be used in evaluating many different aspects of tunnel maintenance and repairs from structural aspects like the example above to fan model selection for the mechanical ventilation system to which light bulb manufacturer is better over the long term. There are multiple reference materials that could be of assistance if a more detailed analysis is desired.
GLOSSARY AC ACI ADT AWS BART CIP CO2 DC FHWA FTA MTS NACE NETA NFPA PVC OSHA SCADA SEM TBM USDOT Alternating Current American Concrete Institute Average Daily Traffic American Welding Society Bay Area Rapid Transit Cast-In-Place Carbon Dioxide Direct Current Federal Highway Administration Federal Transit Administration Maintenance Testing Specifications National Association of Corrosion Engineers InterNational Electrical Testing Association National Fire Protection Association Polyvinyl Chloride Occupation Safety and Health Administration Supervisory Control And Data Acquisition Sequential Excavation Method Tunnel Boring Machine United States Department of Transportation
Tunnel Maintenance and Rehabilitation Manual G-2 Federal Transit Administration .
Chapman & Hall. State-of-the-art of Non-destructive Testing Methods for Determining the State of a Tunnel Lining. 1996. Association Francaise des Travaux en Souterrains (AFTES) Working Group No. Concrete Repair and Maintenance Illustrated. Sandfort and J. J. Farmington Hills. Arnoult. Schreyer. Tunnelling and Underground Space Technology.. A..4 (1995): 413-431. Means Company. T. May 1995. American Concrete Institute. C. ACI 224. How to Prevent Tunnel Ice-up.html. S. G. Causes. Utah Department of Transportation. Jackel. R. Inc. Emmons. Dell’Isola.. Protective.9 used with permission from Elsevier Science) Barlo. and G. Inc. ACI 515.acns. Manual for Railway Engineering.7. Construction. Means Company.. 1999. and 4. 14 (Maintenance and Repair of Tunnels).. 1986. Life-Cycle Cost Analysis Instructional Manual. MA.1R-93 (Reapproved 1998).8. P. J.3 (1989): 343-407. 4. R. Second Edition. Tunnels & Tunnelling International. King. R.J. Dampproofing. MI. Federal Highway Administration R-1 . Value Engineering: Practical Applications…for Design. 12/7/2001. H. Volume 1 and 4. Culvert Inspection Manual FHWA – IP – 86 – 2. Stray Current corrosion in electrified Rail Systems – Final Report. Farmington Hills. J. and T. 1986. 10. Kuesel. Evaluation and Repair of Cracks in Concrete Structures. Federal Highway Administration.Tunnel Maintenance and Rehabilitation Manual REFERENCES American Concrete Institute (ACI) Committee 515.nwu. Tunnelling and Underground Space Technology. http://iti. and Decorative Barrier Systems for Concrete. 1993. New York. Elliott. MI. 1994. J. 4. MA. Kingston. Bickel. American Concrete Institute. E. AREMA. D. Zdunek. American Concrete Institute (ACI) Committee 224. Manual for Maintenance and Inspection of Constant Tension catenary Systems.edu/projects/stray2. A Guide to the Use of Waterproofing. November 1995. 1994 Haack.. Engineering Services Division. May. M. Maintenance & Operations. American Railway Engineering and Maintenance-of-Way Association (AREMA). 1998. pp. (Figures 4. Kingston. A. S. Tunnel Engineering Handbook... 42-43. Recommendations for the Treatment of Water Inflows and Outflows in Operated Underground Structures. M. Metro-North Commuter Railroad. A..1R-79 (Reapproved 1985).
L. Code of Federal Regulations. Sperry Rail Service. Rail Defect Manual. Bridges. Simmons-Boardman Books. Trends in Rock Mechanics. Department of Transportation. 2001. Title 49. 1998. Electric Traction Catenary Inspection Field Manual. and Appliances. Class of Track 1-5. Richards. U.S. Devices. R-2 Federal Transit Administration . Maintenance and Repair of Tunnels: International Lessons and Practice. and Other Limited Access Highways. 102. 2001. National Fire Protection Association. Code of Federal Regulations.S. P. Geotechnical Special Publication No. Department of Transportation.E. U. Title 49.. Methods. Standards.S.. Rules. Inc. and Repair of Signal and Train control systems. Federal Railroad Administration – Office of Safety. A.. J. Part 236. New York. 13. 1968. American Society of Civil Engineers Proceedings of Sessions of GeoDenver 2000. Part 220. U. McGraw-Hill. Structural Renovation of Buildings. Inspection. 2001.4 (1998): 369-375. Newman. Federal Railroad Administration – Office of Safety. AMTRAK. NY. NE.. A. Tunnelling and Underground Space Technology. Track Safety Standards Part 213. 2001.Tunnel Maintenance and Rehabilitation Manual Narduzzo. SYSTRA Consulting. and Instructions Governing the Installation. Code of Federal Regulations. Inspection. Maintenance. Department of Transportation. Sperry Rail Service. 2001. Subpart A to F. Details. Title 49. Federal Railroad Administration – Office of Safety.. Railroad Communications. Omaha. Tunnel Leak Remediation at the Toronto Subway. and Design Examples. NFPA 502: Standard for Road Tunnels.
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