bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface-Smoothness Evaluation and Specifications for Flexible Pavements
Authors: Uddin W , Hudson WR , Elkins G
Published: March 2009

The quality of smoothness of a newly constructed or overlaid pavement dictates the beginning of pavement management. Adequate acceptance testing procedures and specifications for pavement smoothness have not been available for flexible pavements. Smoothness specifications based on a 10-ft (3.05 m) straightedge has a number of limitations and is difficult to interpret and administer. This paper describes the results of a comprehensive study of several different roughness measuring devices undertaken to select a suitable device in order to develop and implement improved specifications for pavement smoothness. The candidate devices included the 690D Profilometer, Model 8300 Roughness Surveyor, Maysmeter, California Profilograph, and Rainhart Profilograph.

In this study, the 690D Profilometer ranked highest in overall performance. The paper describes the benefits and negative aspects of each type of equipment related to its use for surface-smoothness measurement and acceptance testing of newly constructed pavements and pavement overlays. The results are useful for any agency desiring to improve its smoothness measurement and acceptance testing procedures.
The Noss Roughness Meter: A Norwegian Road-Roughness Measurement System
Authors: Noss PM
Published: March 2009

The development of a new Norwegian device for the measurement of road roughness started in 1985. A prototype is now finished. Tests demonstrate that longitudinal profiles of wheeltracks measured with this equipment meet the requirements to qualify as “Class 1: Precision profiles” [1], which represent the highest standard of accuracy for measurements of the International Roughness Index (IRI).

The longitudinal profile is given as elevation points with 25-cm spacing along the measured wheeltrack, and different criteria for road roughness can be computed from this profile. In February 1988, necessary software was completed to compute IRI as described by The World Bank [1]. In addition, computed straight-edge values can be presented as histogram for any section length chosen by the operator.

The measurements are independent of traveling speed, and the calibration of the equipment is very simple. The production of the first series of the equipment will start in 1988, and it will be used both for detailed studies on test sections and for road network surveys in Norway.
The Prediction of Pavement Ride Quality from Profile Measurements of Pavement Roughness
Authors: Janoff MS
Published: March 2009

This paper summarizes the results obtained in five different states when profiles were used to develop transforms that predict rideability from pavement roughness. The five individual state transforms are very similar and have similar accuracy and validity. As a result, one transform—derived from the combined data from all five states—can be used to accurately predict rideability from profile measures of roughness in any of the five states.

The resulting transform is applicable to bituminous, Portland cement, and composite surfaces and the three types combined, and to both interstate and other classes of road. Use of this transform provides an efficient and accurate method for determining the rideability of pavement surfaces from physical measures of pavement roughness. This transform provides a basis for a system of measuring and reporting totally comparable roughness and rideability data that can also be used to assist highway agencies to determine when existing pavements should be repaired and to evaluate newly constructed pavements.
High-Performance Measurements for Programming and Controlling Maintenance of Surface Characteristics: Operational Systems in Use on Italian Motorways
Authors: Camomilla G , Malgarini M , Peroni G
Published: March 2009

Maintaining pavement skid resistance depends on the geometric conditions of the road (straights, curves, slopes, etc.), weather conditions (wet or dry surfaces, etc.), and vehicle conditions (condition of brakes, tires, etc.). This paper reports the criteria adopted in establishing the more probable limit values associated with the various characteristics in question which are necessary to maintain safety without sacrificing economic management criteria.

Skid-resistance measurements, together with riding comfort index values, thus serve two main purposes: (1) In construction or maintenance of pavements, they serve as a means of quality control; pavements are deemed to have been laid properly only if certain characteristics correspond to pre-established acceptance requirements, and (2) During normal operations, they serve to pinpoint zones which require special intervention to restore skid resistance and smoothness, also taking into account in critical areas the problems of noise, which are gaining increasing attention here in Europe. These requirements have been spelled out in the technical tender specifications adopted for the IRI-ITALSTAT motorway network and include fines in cases of failure to respect these standards. In like manner, quality-control tests have been developed to assess the trend of skid resistance over time in composite materials taken from actual road pavements (passing the APA tests (Accelerated Polishing of Aggregates Using the British Wheel), which measure just the component materials).

The methodology already presented and proposed for the Italian motorway network, based on high-speed monitoring equipment such as the ARAN III, the longitudinal profile analyzer (APL), and the SUMMS (Survey Machine for Macrotexture and Skid, derived from the SCRIM), should ensure lasting, safe, and comfortable pavements obtained at optimal costs.
Errors in Automated Pavement Surface Distress Data Collection
Authors: Humplick F , McNeil S
Published: March 2009

The massive condition inventory for highway systems requires continual inspection of pavement surface condition to evaluate pavement performance and make management related decisions. Typically, this requires intensive data collection in short periods of time, to make long-term predictions. Automated imaging techniques have been developed to obtain visual data quickly and efficiently. The automation process creates large amounts of data, most of which are removed during processing to highlight features of interest.

The pavement management process uses the results of measurement from these automated techniques for prediction and decision making. This process is very much affected by the accuracy of the measurements and the continual loss of accuracy at each processing stage. This loss of accuracy, in the most part, has been ignored in existing management systems.

This paper describes and illustrates error estimation techniques for automated data collection processes that model errors in the imaging system, data processing, and subjective input to processing. These accuracy estimation techniques can be used to assess the quantity of data needed, the appropriate quality of data, and the frequency of data collection. Finally, this analysis can be incorporated into the pavement management process as an error diagnostic system to aid in estimation and prediction of pavement performance, maintenance and rehabilitation expenditures, and to recommend or select data collection technologies.
Measurements and Criteria: Essential Elements for Pavement Management
Authors: Jordens R , de Wit B
Published: March 2009

A systematic approach has been developed for planning the long-term maintenance of flexible pavements. This has resulted in a multi-year planning system which not only provides information about the type of maintenance required, but also details the cost and timing involved. Visual inspections are carried out to characterize the condition of the roads, coupled with rut depth and longitudinal evenness measurements. By comparison of the results of such tests with predefined guidelines, maintenance activities can be planned in a systematic way.

The choice of representative parameters to characterize the quality of the road network is outlined in this paper, as is the philosophy regarding maintenance guidelines. Furthermore, the measuring and inspection techniques employed are reviewed and the effects of possible errors discussed. Finally, recommendations are made as to how the system can be improved. The introduction of an automated data-collection system for surface distresses is seen as having the highest priority.
Impact of Roughness-Induced Dynamic Load on Flexible Pavement Performance
Authors: Papagiannakis AT , Haas RCG , Woodrooffe JHF , Leblanc PA
Published: March 2009

This study deals with the impact of roughness-induced dynamic load on flexible pavement distress and performance. It involves field measurements of dynamic axle loads using the instrumented vehicle developed by the National Research Council in the context of the Road and Transportation Association of Canada Weights and Dimensions Study. Pavement distress and performance are modeled using a modified version of the Federal Highway Administration's (FHWA) VESYS-III-A model.

Measured standard deviations of dynamic load ranged from 8 to 42 kN, depending on vehicle speed, pavement roughness, and suspension type where the corresponding static load values were approximately 205 kN. It was concluded that for vehicle speeds higher than 40 km/h, the rubber suspension yields dynamic loads substantially higher than the air suspension. Furthermore, dynamic load waveforms from replicate runs were found repetitive in space. Although this loading condition is clearly not the case for pavements under in-service traffic, it was typical of the loading experienced by American Association of State Highway Officials (AASHO) Road Test sections. As a result, the latter is considered poorly randomized with respect to the impact of dynamic load.

A method is described for modeling the impact of the repetitive in space dynamic load experienced by a number of AASHO Road Test sections. Ten sections were analyzed, six of which developed severe roughness through their service lives. The methodology improved considerably the accuracy of performance predictions for four out of the six rough sections analyzed. Another part of the study examined the impact of suspension type on pavement performance assuming random application of dynamic loads. Performance predictions for the two suspensions were compared on the basis of the relative areas under the performance curves. With respect to the static load, the rubber suspension caused 17 and 22% additional damage for terminal serviceability values of 2.0 and 2.5, respectively. The corresponding values for the air suspension were 6 and 8%, respectively.
Road-Surface Influence on Tire Rolling Resistance
Authors: Descornet G
Published: March 2009

A unique “quarter-car” trailer has been designed and built at the Belgian Road Research Center for measuring the rolling resistance of a reference tire on the road. Its design and performances are briefly outlined. It has been used for investigating the influence of road-surface characteristics on the rolling drag experienced by a car tire. On a wide variety of surface types and conditions on dry paved roads, the coefficient of rolling resistance ranges between 0.013 and 0.021. In terms of fuel consumption, this can be converted into 9% relative influence of the road surface. With respect to the intrinsic tire rolling resistance coefficient (0.010) as measured on a particularly smooth and even test track, the worst road surface can double the rolling resistance. The main surface-related influencing factor has been found to be surface profile irregularities in a wavelength range lying between macrotexture and un-evenness, namely megatexture (50 mm < wavelengths < 500 mm), which had already been reported as responsible for tire/road noise.
Road Conditions and Accidents in Winter
Authors: Hagiwara T , Onodera Y , Fujiwara T , Nakatsuji T , Kaku T
Published: March 2009

Skidding resistance on snowy and icy roads is much less than that on clear roads; hence, it may be said that, in many cases, traffic accidents under such road conditions are closely related to skidding. We investigated the road conditions, skidding-resistance value, and their relationship to traffic-accident rates during winter. The model that estimates the number of days of slippery road conditions is constructed. Monthly days of slippery road conditions in 1982, 1983, and 1984 are calculated by using this model. We carried out measurements of the skid-resistance number on slippery road surfaces on Hokkaido, comprising approximately 5000 individual skid tests on slippery road surfaces. An accident-rate predictive model for winter is designed from the road conditions and the meteorological conditions. Road-surface conditions under no-snow conditions during winter is assumed, and reduced number of accidents are estimated.
The Influence of Pavement Evenness and Macrotexture on Fuel Consumption
Authors: Laganier R , Lucas J
Published: March 2009

In order to estimate the influence of evenness and macrotexture of the paved roads on fuel consumption of vehicles, three practical tests have been made: in the laboratory, with a vibrator bench to simulate unevenness; on a track to test the extreme values of the macrotexture of pavements; and on open roads with both unevenness and macrotexture. Pavement characteristics have been recorded with usual apparatus for road engineers. The effects have been expressed as extra fuel consumption, versus a completely smooth and even pavement. Both unevenness and macrotexture show a measurable extra fuel consumption. But the growing laws are not linear, and a compromise can be found for evenness according to maintenance cost and for macrotexture according to safety when wet.
Road Macro- and Megatexture Influence on Fuel Consumption
Authors: Sandberg USI
Published: March 2009

An experiment was conducted in which a specially instrumented Volvo 242 car was run at 50, 60, and 70 km/h over 20 road surfaces with various textures. Macro- and megatexture as well as the shorter wavelengths of unevenness were measured by a mobile laser profilometer, the signal of which was analyzed to obtain the texture profile spectrum for each surface in the 2- to 3500-mm texture wavelength range.

The fuel-consumption data at each speed and averaged for the three speeds were regressed on the texture profile spectrum data. The results show (1) Fuel consumption varies over a range of approximately 11% from the smoothest to the roughest road tested if texture wavelengths in the range 0.6 to 3.5 m are considered, and approximately 7% if texture wavelengths in the range 2 to 50 mm (macrotexture) are considered. (2) The correlation between fuel consumption and texture is as high as 0.90 (correlation coefficient) in the range 0.6 to 3.5 m and reduces smoothly at shorter wavelengths, down to about 0.60 at wavelengths equal to common maximum chipping sizes on roads. Thus it appears that fuel consumption is influenced very much by road unevenness and megatexture, but somewhat less by macrotexture. (3) Some of the mega- and macrotexture influence is due to a covariation with shortwave unevenness, and the pure effects of each, especially macrotexture, are somewhat less than noted in (1) and (2). (4) The results indicate that significant parts of the losses may occur at frequencies typical of vehicle body and wheel hop resonances and, thus, be dissipated in the car suspension system. (5) The results demonstrate that the road surface quality has a great impact on car fuel consumption, and that the largest potential for improvements may be to control megatexture and, most of all, shortwave unevenness on roads. Also macrotexture is important to control, at least when car speeds of 60 to 70 km/h are common. The unevenness at longer wavelengths has not been covered in this experiment.
Fuel Consumption of Vehicles as Affected by Road-Surface Characteristics
Authors: du Plessis HW , Visser AT , Curtayne PC
Published: March 2009

The relationship between components of vehicle operating costs (VOCs) and highway characteristics has been studied by many researchers over the years, but many issues still remain to be resolved. In particular, although fuel consumption should be the easiest component to model, there is considerable variance between reported results. A comprehensive experiment was therefore designed to investigate the effects of road-surface characteristics on fuel consumption, as a first step toward establishing reliable VOC relations for South African conditions. A passenger car, two medium-sized trucks, and two buses were chosen for coast-down tests to determine rolling resistance over a series of road sections, covering the ranges of surface conditions encountered locally. The models developed predict that at constant speeds on level roads, road-surface characteristics can affect the fuel consumption of passenger cars by up to 7% and that of trucks and buses by up to 20%. It is believed that these models can be applied with confidence in practice, considering the comprehensive nature of the experiment.
Measurement of Rolling Resistance Using an Eccentrically Weighted Oscillating Wheel
Authors: Hill BJ
Published: March 2009

A method is developed for measuring small changes in rolling resistance between different types of bicycle racing tires. The method described has been used specifically to assist in the choice of tires to be used on a special-purpose vehicle entered in an event where the aim is to use the least amount of fuel over a set distance. The rolling resistance is determined by considering the loss in energy when an eccentrically weighted pair of wheels is allowed to oscillate backwards and forwards on a level surface. The procedure was found to give repeatable results and was able to resolve the differences between a number of tires of low inherent rolling resistance. It is concluded that the oscillating wheel method is useful for determining rolling resistance losses in the laboratory and in the field and is able to resolve small changes in losses due to changes in the operating parameters.
Optimization of Road-Surface Characteristics: A Concept for a Research Program in the Federal Republic of Germany
Authors: Hiersche E-U
Published: March 2009

In recent years, the research activities in the Federal Republic of Germany in respect to road-surface characteristics have concentrated mainly on maximizing or minimizing single road-surface characteristics. Now the optimization of all road-surface properties as a whole has priority as an actual aim within a research program. This paper describes the influences, basic characteristics, derived characteristics, and objectives for an optimization process and their many mutual relationships. A ranking of these relationships is also given.
Analysis and Evaluation of the Performance of Porous Asphalt: The Spanish Experience
Authors: Pérez Jiménez FE , Calzada Pérez MA
Published: March 2009

The excellent qualities of pervious wearing courses which enhance road safety and comfort are well known. However, there are very few test and control methods which allow these courses to be planned and used adequately. The design of the porous asphalts used in the construction of these pervious wearing courses depends on a number of rules of thumb derived from their use, but there is no test method or procedure which might allow their properties to be characterized and optimized.

In this paper, we describe the procedure and planning criteria which are used in Spain in the design of porous mixes and which were established both from the behavior of these mixes in use and from the results of tests performed in the laboratory. The procedure used is based on optimizing two fundamental characteristics of these mixes: permeability and resistance to disintegration. We have developed two testing methods which allow both properties to be assessed. Permeability is assessed in situ by means of the Laboratorió de Caminos de Santander (LCS) permeameter and resistance to disintegration is evaluated by means of the Cantabrian abrasion loss test. These two tests optimize the design of these mixes and allow the effect on their behavior of using modified binders to be evaluated. We also describe the effects that these mixes have on adhesion, texture, and noise of the wearing course surface compared with other materials used in road surfacing.
Methods for Sampling Fluids in the Vadose Zone
Authors: Wilson LG
Published: March 2009

This paper reviews available methods for sampling water-borne pollutants in the vadose zone. The “standard” method for sampling pore fluids in the vadose zone is core sampling of vadose zone solids, followed by extraction of pore fluids. The preferred method for solids sampling is the hollow-stem auger with core samplers. Core sampling does not lend itself to sampling the same location time and again. Membrane filter samplers and porous suction samplers are an alternative approach for sampling fluids in both saturated and unsaturated regions of the vadose zone. There are three basic porous suction sampler designs: (1) vacuum-operated suction samplers, (2) pressure-vacuum lysimeters, and (3) high-pressurevacuum samplers.

Suction samplers are constructed mainly of ceramic and polytetrafluoroethylene (PTFE). The effective range of ceramic cups is 0 to 60 cbar of suction. The operating range of PTFE cups installed with silica flour is 0 to 7 cbar of suction. This paper reviews a method for extending the sampling range of suction samplers using an injection-recovery procedure. Factors affecting the operation of porous suction samplers include the physical properties of the vadose zone, hydraulic conditions, cup-wastewater interactions, and climatic conditions. Innovative procedures include the water extractor and the filter-tip system sampler. The free-drainage samplers include pans, blocks, and wick-type samplers. Techniques for sampling from perched ground-water zones include profile samplers, sampling from cascading wells, and sampling from dedicated wells.
Monitoring of Immiscible Contaminants in the Vadose Zone
Authors: Ballestero TP , McHugh SA , Kinner NE
Published: March 2009

The monitoring of nonaqueous-phase fluids in the unsaturated zone can be accomplished with tensiometers or suction lysimeters if care is taken before the instrumentation is installed. In this instance, the porous material used to monitor fluid pressure, or to sample a fluid, should be prewetted with the fluid of interest. Experiments with three-phase fluid flow of immiscible fluids in a porous medium have shown that there is a small window of fluid contents at which all three fluids are mobile. With this in mind, monitoring/sampling of each phase was accomplished for various liquid contents for each of the liquids. More often than not, though, liquid sampling is preferential towards the wetting fluid. For petroleum hydrocarbons, water, and air in porous media and in porous ceramic cups, the dominant wetting fluid has been found to be water.
Tensiometers—Theory, Construction, and Use
Authors: Stannard DI
Published: March 2009

Standard tensiometers are used to measure matric potential as low as -870 cm of water in the unsaturated zone by creating a saturated hydraulic link between the soil water and a pressure sensor. The direction and, in some cases, quantity of water flux can be determined using multiple installations.

A variety of commercial and fabricated tensiometers are commonly used. Saturated porous ceramic materials, which form an interface between the soil water and the bulk water inside the instrument, are available in many shapes, sizes, and pore diameters. A gage, manometer, or electronic pressure transducer is connected to the porous material with small- or large-diameter tubing. Selection of these components allows the user to optimize one or more characteristics, such as accuracy, versatility, response time, durability, maintenance, extent of data collection, and cost.

Special designs have extended the normal capabilities of tensiometers, allowing measurement in cold or remote areas, measurement of matric potential as low as -153 m of water (-15 bars), measurement at depths as deep as 6 m (recorded at land surface), and automatic measurement using as many as 22 tensiometers connected to a single pressure transducer.

Continuous hydraulic connection between the porous material and soil, and minimal disturbance of the natural infiltration pattern are necessary for successful installation. Avoidance of errors caused by air invasion, nonequilibrium of the instrument, or pressure-sensor inaccuracy will produce reliable values of matric potential, a first step in characterizing unsaturated flow.
Experimental Screen Design for More Sediment-Free Sampling
Authors: Rich CA , Beck BM
Published: March 2009

An experimental double-walled screen design has been found to increase the reliability of a properly installed, monitoring well sand pack, intended to produce long-term sediment-free sampling. The screen design is most useful for shallow, small-diameter monitoring wells installed by the hollow-stem auger drilling method and can be produced in a wide range of lengths and diameters. The new screen design eliminates the need for state agencies to require “tremied” gravel packs for such wells when the tremie-pipe installation technique is difficult to complete successfully without compromising the intent behind the specification. The double-walled screen design contains an economically fabricated, preassembled, evenly graded sand pack that avoids the need for resin and that ensures emplacement of an in situ homogeneous sand pack in the field.

When installed directly against the formation wall, in conjunction with a conventional sand pack or the best efforts at a tremied pack, the preassembled double-walled screen and sand pack may help reduce the amount of development time necessary to obtain turbidity-free water (that is, water containing less than 50 nephelometric turbidity units). The presence of the preassembled homogeneous sand pack downhole improves long-term sample integrity in silty deposits and minimizes interference attributable to improperly placed or poorly settled packs. The sand pack example described is simple in design and economical, accommodates small-diameter submersible pumps and bailers, and is easily fabricated in the field.
Monitoring Well Development—Why and How
Authors: Kill DL
Published: March 2009

The objectives of monitoring well development are these: (a) to permit taking of sediment-free samples, (b) to allow water to flow freely into the well so representative samples can be taken rapidly, and (c) to remove all traces of the drilling fluid used in order to minimize any interference with the water quality.

Several development methods have been well documented as to their practicality and effectiveness in developing water supply wells. These methods are mechanical surging, overpumping, air lift, high-velocity water jetting, and several combinations of these methods. All of these methods can be used in monitoring well development but have limitations. Their limitations are usually related to the well diameter, restrictions on placing foreign materials in the well, low-permeability formations, and poor well intake design.

The methods and limitations are reviewed in this paper.
Monitoring Wells: Maintenance, Rehabilitation, and Abandonment
Authors: Winegardner DL
Published: March 2009

This paper presents an overview of the technical considerations and field procedures involved in monitoring well maintenance, rehabilitation, and abandonment. It includes criteria that should be considered throughout the life span of the well to ensure that the well serves its purpose optimally and that, when removed from service, it is no threat to the environment. The primary purpose of this paper is to provide guidance in selecting the most acceptable field procedures.

Even though monitoring wells are intended to be sources of reliable data, each well introduces a number of limited control variables that may affect the reliability of the analytical data. Regular maintenance of monitoring wells, both structurally and hydrologically, is required to preserve optimal performance of the well. Well maintenance principles are discussed in this paper, and recommendations for procedures are provided.

Major changes to a well may be required when it no longer serves its original purpose. The benefits of rehabilitation procedures are discussed and related to the risk of accepting changes in the established data base.

Abandonment (or decommissioning) of monitoring wells is necessary when they no longer serve their intended purpose. At that time, the well must be brought to a neutral condition which is compatible with the soil matrix, ground-water quality, and the chemicals monitored and which also preserves the hydrogeological integrity of the specific location. Examples of successful closures are presented to illustrate these general principles.
Sorption of Aromatic Hydrocarbons by Materials Used in Construction of Ground-Water Sampling Wells
Authors: Gillham RW , O'Hannesin SF
Published: March 2009

Sorption of dissolved constituents from water within a sampling well onto well-casing materials or sampling equipment is frequently cited as a potential source of bias in ground-water sampling programs. This study examined the sorption of six monoaromatic hydrocarbons (benzene, toluene, ethylbenzene, and m-, o-, and p-xylene) onto seven sampling well materials. The materials included stainless steel, rigid polyvinyl chloride (PVC), polytetrafluoroethylene (PTFE), polyvinylidene fluoride, epoxy-impregnated fiberglass, flexible polyvinyl chloride (PVC), and polyethylene. Samples of the test materials were exposed to aqueous solutions containing the six organic compounds for time periods ranging from 5 min to 8 weeks. The concentration remaining in solution, at the end of the exposure period relative to the initial concentration, was taken as a measure of the degree of sorption.

No uptake of any compound onto stainless steel was noted, while some degree of sorption was observed for all compounds on all polymer well-casing materials. Sorption increased with increasing hydrophobicity of the organic compounds. The sorption increased in this order: benzene, toluene, o-xylene, m-xylene, ethylbenzene, and p-xylene. Of the polymer materials, rigid PVC showed the least sorption, followed by fiberglass and polyvinylidene fluoride (which were similar) and PTFE. The flexible tubing, polyethylene, and flexible PVC showed the highest rates of uptake, with significant losses from solution by the first sampling time (5 min).

The experimental data were shown to follow a diffusion model closely, with effective diffusion coefficients corresponding to different rates of uptake from solution. The model was used to extend the experimental results to monitoring wells of different diameter.

Stainless steel and PTFE are commonly recommended as preferred materials for constructing monitoring wells, particularly if organic contamination is expected. Under the conditions of this study, and based only on their relative sorption characteristics, several polymer materials, including rigid PVC, are as advantageous and possibly more advantageous than PTFE.
Methods for Evaluating Short-Term Fluctuations in Ground Water Levels
Authors: Sayko SP , Ekstrom KL , Schuller RM
Published: March 2009

During several investigations of ground water contamination, relatively large fluctuations in ground water levels—which occurred in a time interval shorter than that necessary to collect a round of water levels—were observed. However, because of their short-term nature, it was not possible to collect the data necessary to characterize fully the effects of these fluctuations when using standard water level measurement techniques. Without such a characterization, these short-term fluctuations in ground water levels can seriously impair interpretation of the ground water flow system.

In a case history presented, tidal and other environmental influences were large enough to make a normal round of water level data useless in interpreting ground water flow. Monitoring of water levels at the site for a period of eight days, using electronic water level recording instruments, allowed evaluation of the fluctuations and determination of an acceptable method of collecting site water levels. To evaluate ground water levels properly, multiple rounds of water levels had to be collected and averaged to filter the noise, or short-term fluctuations, from the water level data. Monitoring for these short-term fluctuations in ground water levels should be considered good engineering practice in any ground water investigation.
Presentation of Water Level Data
Authors: Henning RJ
Published: March 2009

Most common methods used to present water-level data are graphical. These include various kinds of hydrographs, such as those showing water level versus time, draw-down versus time or distance, or the level in one well versus that in another. Contour plots in map view are essential for evaluating ground-water flow. Water levels on cross sections are useful in evaluating the relationship between stratigraphic units and water levels. Flow nets can be used in plan or cross-sectional view to estimate flow lines and possible pathways for seepage.
A Comparison of Two Multiple-Level Ground-Water Monitoring Systems
Authors: Ridgway WR , Larssen D
Published: March 2009

In the context of the Canadian Nuclear Fuel Waste Management Program, Atomic Energy of Canada Ltd. (AECL) is conducting research into the underground disposal of nuclear fuel waste deep in stable plutonic rock. As part of this research, AECL has developed and tested many geotechnical instrumentation systems. Two multiple-level ground-water monitoring systems have been used to evaluate hydrogeological conditions in fractured rock and overburden materials: the Waterloo system and the Westbay system. Both instruments are designed to isolate several sections of a single borehole for ground-water measurements. The instruments were tested in adjacent boreholes drilled to about 60-m depth in granitic rock at the AECL's Atikokan research area in Ontario, Canada. Various aspects of these instrument systems, including the design, testing and sampling methods, and ground-water measurement data are compared. The information contained in this paper may assist future users to determine if these systems, or other systems, will be effective for their applications.
Total Versus Dissolved Metals: Implications for Preservation and Filtration
Authors: Pennino JD
Published: March 2009

Review of ground-water quality data obtained from wells in southwestern Ohio revealed the presence of lead, cadmium, and other heavy metals. Often, no pollution source could be discovered to account for the presence of the heavy metals. In order to establish whether sampling methods were a possible source of contamination, three possible sources of spurious heavy metal values were investigated: (1) the sample preservative, (2) the sampling equipment, and (3) suspended matter in the samples.

The results of this study indicate that painted labels on nitric acid preservative ampules, used during the period 1978 to 1980, contributed to false indications of ground-water pollution. Tests of galvanized steel and polyvinyl chloride bailers showed that this equipment was not a source of lead or cadmium. Statistical analysis of a random sample of ground-water analyses from 70 wells revealed a significant relationship between sediment and lead values. Furthermore, lead values generally increased as the amount of sediment in the sample increased. This relationship probably reflects the presence of lead in particulate matter in the water sample.

Particulate matter found in well water samples can be pieces of corroded well casing or fine sediment from the formation in which the well is screened. Since very little information is available on heavy metals in Ohio's glacial deposits, additional studies of these materials should be done to provide background data for the evaluation of heavy metals in ground water.
How Flat Is Flat?—Termination of Remedial Ground-Water Pumping
Authors: Spreizer GM , Maxim D , Valkenburg N , Hauptmann M
Published: March 2009

Remedial actions are being initiated at many Superfund sites, and the analyses of water-quality data from these sites are being performed. The start of remediation is obvious—the system used for cleaning up is turned on; however, the determination of when this remediation is “complete” may not be clear.

With the initiation of a remedial measure, it is expected that the detected concentrations of characteristic contaminants will decrease rapidly and then level off to some asymptotic concentration. This is expected since the efficiency of remediation is generally considerably greater at higher concentrations than at lower concentrations. It is expected that some form of an exponential model, y = Cexp (-kx), will describe the system's behavior. This is especially true when ground-water pumping is the remedial measure used, as is considered in this paper.

With Superfund remediation schemes, cleanup or performance goals are set for key compounds. The cleanup is complete when these goals are attained. However, attainment of cleanup goals may be technically infeasible in certain cases and alternative criteria may be appropriate.

This paper presents a statistical methodology, based on an anticipated exponential decrease in the contaminant concentration resulting from ground-water pumping remediation. The methodology will initially predict when remedial measures can be terminated. As the remediation program continues and additional monitoring data become available, the methodology will determine whether and when preestablished concentration limits will be attained and when the equilibrium concentration can be estimated.
Evaluation of Finite-Element Models and Stress-Intensity Factors for Surface Cracks Emanating from Stress Concentrations
Authors: Tan PW , Raju IS , Shivakumar KN , Newman JC
Published: March 2009

This paper presents an evaluation of the three-dimensional finite-element models and methods used to analyze surface cracks at stress concentrations. Previous finite-element models used by Raju and Newman for surface and corner cracks at holes were shown to have “ill-shaped” elements at the intersection of the hole and crack boundaries. These ill-shaped elements tended to make the model too stiff and, hence, gave lower stress-intensity factors near the hole-crack intersection than models without these elements. Improved models, without these ill-shaped elements, were developed for a surface crack at a circular hole and at a semicircular edge notch. Stress-intensity factors were calculated by both the nodal-force and virtual-crack-closure methods. Both methods and different models gave essentially the same results. Comparisons made between the previously developed stress-intensity factor equations and the results from the improved models agreed well except for configurations with large notch-radii-to-plate-thickness ratios.

Stress-intensity factors for a semi-elliptical surface crack located at the center of a semicircular edge notch in a plate subjected to remote tensile loadings were calculated using the improved models. A wide range in configuration parameters was considered. The ratio of crack depth to crack length ranged from 0.4 to 2; of crack depth to plate thickness from 0.2 to 0.8; and of notch radius to plate thickness from 1 to 3. The finite-element or nonsingular elements models employed in the parametric study had singularity elements all along the crack front and linear-strain (eight-noded) elements elsewhere. The models had about 15 000 degrees of freedom. Stress-intensity factors were calculated by using the nodal-force or virtual-crack-closure method.
Fracture Analysis for Three-Dimensional Bodies with Surface Crack
Authors: Yingzhi L
Published: March 2009

This paper deals with fracture analyses in three-dimensional bodies containing a surface crack. A general solution of stress-strain fields at the crack tip is proposed. Based on the stress-strain fields obtained, a high-order, three-dimensional special element is established to calculate the stress-intensity factors in a plate with surface crack. The variation of stress-intensity factors with geometric parameters is investigated.
On the Semi-Elliptical Surface Crack Problem: Detailed Numerical Solutions for Complete Elastic Stress Fields
Authors: Blom AF , Andersson B
Published: March 2009

The p-version of the finite-element method together with carefully designed meshes is used to obtain accurate numerical solutions for complete elastic stress fields in a linearly elastic plate containing a semi-elliptical surface crack for two materials having a Poisson's ratio of 0.3 and 0.499, respectively. A priori known convergence properties are used to estimate bounds for the error in the numerical solutions. The calculated displacements are believed to be accurate at all points located not closer than 0.001a, a being the crack size, from the crack front.

It is demonstrated that pointwise values for the traditional edge stress-intensity factors KI are readily obtained with very high accuracy even when a very simple mesh and a modest computational effort are used. So-called vertex and vertex-edge intensity factors are derived which together with numerically determined eigenfunctions fully characterize the complete solution in the vicinity of the vertex where the crack front intersects with the stress-free surface.

For the nearly incompressible material, the second-order vertex intensity factor strongly influences the solution close to the vertex. In fact, the first-order vertex intensity factor, under different boundary conditions, may be of negligible importance (except for extremely small distances from the vertex). The size of the domain where the vertex singularity strongly influences the solution is of the order 0.02a.
Optical and Finite-Element Investigation of a Plastically Deformed Surface Flaw Under Tension
Authors: Olinkiewicz JC , Tippur HV , Chiang FP
Published: March 2009

A combined moiré method has been used to experimentally obtain three-dimensional surface deformations in a plastically deformed tensile strip containing a surface flaw. A finite-element approach using experimentally obtained displacements as boundary conditions is followed to investigate the interior deformation fields and to study several parameters of interests such as J, crack-tip singularity and J, crack-mouth opening displacement equivalence for a chosen specimen geometry.
Fracture Behavior Prediction for Rapidly Loaded Surface-Cracked Specimens
Authors: Kirk MT , Hackett EM
Published: March 2009

The feasibility of predicting the fracture behavior of surface cracks from shallow cracked bend specimens was investigated. The material studied was a high-strength steel stress relief embrittled to various levels of Charpy-V notch impact toughness. Material toughness was quantified in terms of the J-intergral at total specimen failure (Jcrit, using both deeply notched and shallow-notched bend bars (single-edge notch bend) [SE(B)] dynamically loaded in a drop tower impact testing machine. These data were compared with the fracture behavior of rapidly pressure loaded part-through surface cracked bend [PS(B)] specimens, which had a shallow surface flaw introduced at the specimen midspan. For highly embrittled material (Charpy V-notch energy (CVE) between 10 J and 24 J), Jcrit values measured using shallow crack SE(B) specimens were consistently higher than deep crack Jcrit values due to the shorter crack size, as well as increased plastic energy dissipation within the specimen. These higher Jcrit values served as better predictors of the PS(B) fracture performance than did comparable deep crack values. Even though Jcrit cannot be considered a geometry independent measure of fracture toughness for shallow through cracks, values of this parameter determined using test specimens containing them appear to have considerable engineering utility for predicting the fracture behavior of part-through surface flaws.
Surface Cracks in Thick Laminated Fiber Composite Plates
Authors: Chatterjee SN
Published: March 2009

Application of fracture mechanics to through cracks in thin laminated composite plates does not yield good correlation with test data because of large zones of surface damage near the crack tips. However, for thick laminates with through or surface cracks of moderate sizes (of the order of several ply thicknesses), influence of damage zones is usually small and stress analyses based on homogenization assumption and fracture mechanics approach should yield reliable estimates of failure loads. In this paper, stress-intensity factors for elliptic cracks in transversely isotropic (in planes perpendicular to the cracks) and ortho-tropic media obtained from numerical solutions are reported. In addition, appropriate correction factors to obtain stress-intensity factors for surface cracks of semielliptic shapes are estimated using a limited number of finite-element results. Test data available in literature are correlated with analytical predictions for failure of critical ligaments. Other relevant failure mechanisms are also discussed.
Surface Crack Analysis Applied to Impact Damage in a Thick Graphite/Epoxy Composite
Authors: Poe CC , Harris CE , Morris DH
Published: March 2009

The residual tensile strength of a thick graphite/epoxy composite with impact damage was predicted using surface crack analysis. The damage was localized to a region directly beneath the impact site and extended only part way through the laminate. The damaged region contained broken fibers, and the locus of breaks in each layer resembled a crack that was nearly perpendicular to the direction of the fibers. In some cases, the impacts broke fibers without making a visible crater. The damage was represented as a semielliptical surface crack of the same width and depth as the cross section of the damage. The maximum length and depth of the damage were predicted using the Theory of Elasticity and a maximum shear stress criterion. The predictions and measurements of strength were in good agreement.
A Novel Procedure to Study Crack Initiation and Growth in Thermal Fatigue Testing
Authors: Marchand NJ , Dorner W , Ilschner B
Published: March 2009

An induction heating procedure coupled with an advanced alternating-current potential drop (ACPD) system to study thermal fatigue crack initiation and growth is presented. This technique can be adapted for various specimen geometries and is well suited for studying isotropic as well as anisotropic alloys. Details of the experimental apparatus and ACPD system are given. To illustrate the procedure, the effect of three cyclic thermal histories on the number of cycles to crack initiation of double-edge wedge specimens of IN-100 and MA-6000 superalloys was studied in air. The thermoelasto plastic finite-element analyses (FEA) to determine the critical locations and their respective stress-strain histories are presented. For this particular geometry of specimen, the initiation of microcracks about 10 to 20 μm in length could be detected and crack growth rates lower than 1 μm/cycle were measured. The experimental results combined with the FEA showed that the peak compressive strains encountered on specimen heat-up are more critical to crack initiation and surface degradation than total stress or strain ranges.