Source: https://www.scribd.com/document/296853723/Underpinning-Foundations
Timestamp: 2019-04-23 09:19:14+00:00

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Presented by Alexander Newman, P.E.
 Introduction: Why strengthen foundations?
 FHWA-RD-75-130, Lateral Support Systems and Underpinning, V.
Can We Establish the Existing Pressure on Soil?
General Approach and Methods  Determination of In-Situ Foundation Pressure  Per ASTM D1194  Pit > 3’ x 3’  Access tunnel > 18” wide  Equipment: –Hydraulic ram w/press. stiff clay 9 FEMA 547 General Approach and Methods  Methods of Foundation Strengthening  Adding supports in lieu of foundation strengthening  Shoring and replacement  Underpinning .Alexander Newman. P.E. gage –Load cell –1” thick plate 12’x12” –(4 min) dial gages to measure soil deformation  Best for sand/gravel. helical piers  Modifying soil properties  Connecting to adjacent footings with deep tie beams 10 FEMA 547 5 . micropiles.Pit .By drilled piers.
the most cost-effective  Consider first 11 Adding Supports  Adding Wall Foundations Alongside Existing 12 FEMA 547 6 .Alexander Newman. P.E. Adding Supports  Adding Supports in Lieu of Foundation Strengthening  Often.
E. III. Shoring and Replacement  Using Needle Beams for Temporary Shoring  For replacement or underpinning 13 FHWA-RD-75-130. April 1976 Shoring and Replacement  Inclined Temporary Shoring 14 FHWA-RD-75-130. P. V. 1976 7 .Alexander Newman. V. Lateral Support Systems and Underpinning. Lateral Support Systems and Underpinning. III.
E.Alexander Newman. P. Shoring and Replacement  Foundation Placed in Wrong Location 15 Shoring and Replacement  Another Foundation Placed in Wrong Location 16 8 .
Underpinning  Underpinning  A process that transfers load to a greater depth than original  Used to lower or to enlarge footing  Temporary support is expensive and may not be needed if soil is good and foundation strong  Pit Underpinning vs.c. Using Micropiles.E. Peraza. 17 Underpinning  Pit Underpinning of Walls  Some say: Under favorable conditions. P.Alexander Newman. Etc. 18 Photo: David B.E. can place pits 16’ o. P. 9 .
same depth  Continue excavation  Place concrete… 19 FHWA-RD-75-130. III. its size  Pack soil behind sheeting  1st excavation pit. V. III. P. Lateral Support Systems and Underpinning. V.E. Underpinning  Pit Underpinning Existing Wall Foundations  If OK w/o temporary support  Approach pit. April 1976 20 10 . 48 hrs for regular  Can settle < ½” from: Concrete shrinkage Soil deformation Loss of ground Deflection of existing structure FHWA-RD-75-130.Alexander Newman. Lateral Support Systems and Underpinning. April 1976 Underpinning  Pit Underpinning. Cont’d  Transfer load using drypack or shims after > 24 hr for high-early cement.
E.2. P. P.E. Underpinning  Underpinning Column Footings in Quadrants  Excavate and brace soil around footing  Drive rebars through soil.4 22 11 . place concrete  Wait a few days. Underpinning  Example of Pit Underpinning of Wall 21 Photos: David B. do other quadrants Sequence: 1.3. Peraza.Alexander Newman.
Alexander Newman.E. Underpinning  Underpinning Column Footings in Quadrants. Cont’d 23 Underpinning  Pit Underpinning: Potential Problems  Rubble foundations: May not be feasible to underpin  Perhaps place a retaining wall alongside for excavation support  Use other methods (below) 24 12 . P.
Underpinning  Pit Underpinning: Potential Problems. December 2006 13 .E. Structure. P. bldg. Peraza. Structure. soldier piles and lagging) Can collapse into pit excavation. 26 Source: David B. church vacated  Sandy soils May settle if vibrated. Getting to the Bottom of Underpinning.Alexander Newman. both at perimeter and interior (from piles in adj. settlement . do a preconstruction survey  Establish benchmarks on adjacent buildings…  …Place vibration sensors there to monitor peak particle velocity generated by construction  Place crack monitors over existing cracks  Keep excavating contractor from excavating too much and too fast ahead of underpinning work! Need close coordination (by GC?). building loses support 25 Source: David B. Getting to the Bottom of Underpinning. Cont’d  High water table with silts and clays Example: Hi-rise building next to church… Underpinned perimeter. but interior foundations settled w/dewatering => cracks. December 2006 Underpinning  Pit Underpinning: Reducing Problems  Engage a monitoring firm (by owner). Peraza.
 Underpinning by Drilled Underpinning Piers. Piles and Minipiles  When soil cannot support pits or bearing strata is too deep  Needle Beams and Drilled Piers  C-I-P piers in uncased holes or piles for gravity load & uplift  Requires interior access by equipment FEMA 172 27 Underpinning  28 Underpinning by Drilled Piers FEMA 547 14 .Alexander Newman.E. P.
III.E. P. Underpinning  Wall or Column Footing Underpinned by Piles Placed Alongside FHWA-RD-75-130.Alexander Newman. V. Lateral Support Systems and Underpinning. April 1976 29 Underpinning  30 Adding Piles/Piers to Existing Wall Footing FEMA 547 15 .
E.Alexander Newman. Underpinning  Underpinning Column Footings by Drilled Piers or Piles Through Footing  If footing is large enough 31 US Army TI 809-05 Underpinning  Two Piles/Cantilever Beam 32 16 . P.
Lateral Support Systems and Underpinning. V. V.Alexander Newman. April 1976 17 . Lateral Support Systems and Underpinning. III.E. April 1976 33 Underpinning  Underpinning by Augered Pile Installed in Slot  Specialized equipment needed to cut the slot 34 FHWA-RD-75-130. Underpinning  Underpinning by Jacked Piles  When DL is large  Use open-ended pipe or H section  Place in pits made as in pit underpinning  Fasten a steel plate at bottom of footing and to top of pile. III. P. place jack in between and blocking  Splice pipe and continue FHWA-RD-75-130.
Lateral Support Systems and Underpinning.E. V.Alexander Newman. Underpinning  Underpinning by Augered Concrete Caisson With Bracket  Pit needed for bracket  For smaller loads: C-I-P piers (say. April 1976 18 . Lateral Support Systems and Underpinning. P. III. V. III. April 1976 35 Underpinning  Underpinning by Steel Pile with Bracket  Pile can be augered or driven 36 FHWA-RD-75-130. 12” dia) w/ column-type rebars & haunch FHWA-RD-75-130.
III. Lateral Support Systems and Underpinning. 1976 19 . 38 FHWA-RD-75-130. 37 Underpinning  Micropiles: Typical Uses Can be spaced closer. may have to stabilize existing masonry if piles are driven thru it. P. Needle. Underpinning  Using Micropiles (Minipiles. so existing structure span is less. V. Root Piles) ― Small diameter ― Design loads from 3 to 500+ tons ― Can be readily designed for tension/uplift loads ― Appropriate for a wide range of ground conditions ― Suitable for low headroom and restricted access ― Low noise and vibration ― Can penetrate obstacles Source: Hayward Baker. Inc.Alexander Newman..E. Pin. Still.
Inc.E. most soils where direct pressure grouting is not possible 40 Hayward Baker. Inc. 39 Underpinning  Types of Micropiles  Driven: Light loads thru soft soil  Compaction grout: Shallow depth. loose. P. 20 . sandy soils (by blast of compressed air)  Jet grout: High capacity. Design pile-to-structure connection 4. Geotechnical study 2. Design pile-to-soil or rock load transfer 5. to 2x static load) Source: Hayward Baker. Determine load to be supported 3. Underpinning  Typical Micropile Design Steps 1.Alexander Newman. Develop a pile testing program (typ.
P. wide range of soils. Underpinning  Types of Micropiles.Alexander Newman. Inc. end bearing: Small diameter. Post-grouting enhances friction capacity of pile  Pressure grouted: High capacity.E. enhanced friction capacity by densification & grout permeation of soil  Drilled. Cont’d  Post grouted: All soils. Underpinning  Typical Grouted Micropile Construction  Detail next 42 FEMA 547 21 . can transfer high loads to till or rock 41 Hayward Baker.
E.Alexander Newman. but there was a theater was built around two of them… Access could only be through a pair of 6 foot high doors  Solution: Minipile installation w/low overhead drill rig 44 Hayward Baker. Mo. 22 .   Problem: Seismic upgrade of I-70/64 bridge column foundations was needed. Inc. bottom for compression 43 FEMA 547 Underpinning Example: Using Minipiles for Seismic Retrofit of Union Station Theater. St. P. Underpinning  Grouted Micropile Connection Details  Top plate for tension (placed deep enough into footing). Louis.
Underpinning  Minipiles for Seismic Retrofit. Underpinning  Minipiles for Seismic Retrofit. place high-strength (150-ksi) bar & grout  Bearing plate on top of bar + shear studs 45 Hayward Baker. P.Alexander Newman. Cont’d  Bar placed in black corrugated plastic & space within grouted Existing column and excavated foundation Completed minipile with cap and rock anchor 46 Hayward Baker. Inc.E. Cont’d  Minipile: pipe to rock. then drill into rock 18’  Flush rock hole. High capacity rock anchors with corrosion protection 23 . Inc.
doweled into existing column 47 Hayward Baker.Alexander Newman.E. Inc. Cont’d  48 Hayward Baker. Underpinning Example: Underpinning with Minipiles to Repair Settlement in a SE Florida Parking Garage. Inc. Underpinning Example: Minipiles for Repair of Settlement.25’ firm sand / dense sand & limestone  But: One interior isolated column began settling  SPT at that location found isolated pocket of 0 – 13’ sand fill / 7’ organics / dense sand & limestone  Solution: Minipiles installed w/low overhead drill rig. shallow foundations with 4 ksf  Assumed soil: 0 . 24 . P.   Problem:  Three story precast parking garage.
Solid Earth Technologies. Cont’d  Hayward Baker. Inc. 49 Underpinning  Using Proprietary Steel Anchors  Helical PulldownTM Anchors (AB CHANCE® Anchors)  Good sources of info: .solidearthtech. http://www. Inc. P.Alexander Newman.AB Chance Co.com 50 Solid Earth Technologies.com . www. Inc. Underpinning Example: Minipiles for Repair of Settlement.abchance.E. 25 .
MO 64056 Telephone: (816) 796-6800.E. Inc. Inc.Alexander Newman. Enlarging Footings  Enlarging Existing Footings 52 FEMA 547 26 . INC. and Atlas Systems. P.com 51 Hayward Baker. Underpinning  Jacked Steel (Atlas) Piers  End-bearing piers hydraulically pushed to load bearing strata  ATLAS SYSTEMS. web http://www. Independence. 1026-B South Powell Road.atlassys.
Alexander Newman. London. London. McGraw-Hill Int’l. Structural Aspects of Building Conservation. 1995 27 . Structural Aspects of Building Conservation. McGraw-Hill Int’l. 1995 Enlarging Footings  Assumptions in Widening Foundations.E. Cont’d  Drilled-in SS threaded rods or hooked bars  Threaded SS PT bars in pressure-grouted holes 54 After Poul Beckmann. P. Enlarging Footings  Some Assumptions in Widening Footings  Idealized model with uniform pressure 53 After Poul Beckmann.
Enlarging Footings  Widening Concrete Foundations. Cont’d  Real life: Unequal pressure => more settlement when loaded  Using flatjacks over the pressure slab to preload soil  Preload gradually in clay (weeks) 55 After Poul Beckmann. London. McGraw-Hill Int’l.E. vertical spacing of ~ 2 ft?  Remove finishes to expose joints 56 28 . P. 1995 Enlarging Footings  Widening Rubble Foundations  Pressure grout before underpinning  Grout travels easier horizontally.Alexander Newman. Structural Aspects of Building Conservation.
P.E. Cont’d…  Drill and PT after 28 days  Use to widen the footing or make a beam to span between new deep foundations 58 29 . Cont’d   Cut into existing foundation  Alternate the hooks  Corrosion-resistant coating? 57 Enlarging Footings  Widening Rubble Foundations.Alexander Newman. Enlarging Footings Widening Rubble Foundations.
pump grout as bit is withdrawn). Cont’d  Connect to adjacent footings with deep tie beams  May need a concrete overlay on top of footing  Will concrete overlay on top of footing help? 60 30 . insert deformed rod..Alexander Newman. Other Strengthening Issues  Increasing Uplift Capacity of Column Footings  Increase size by underpinning as above  Add drilled piers or soil anchors (use drill bits from 4” to 6” dia.E. Can PT rods if anchored into grouted soil below casing. 59 Contractors for FEMA use a power drill to place 4ft long steel anchors into sand to tie down FEMA travel trailers in Pensacola. June 2005 (FEMA) Other Strengthening Issues  Increasing Uplift Capacity of Footings. P.
Alexander Newman. cement grouting to bind particles  For fine sands and coarse silts. Other Strengthening Issues  Increasing Lateral Resistance of Column Footings  Increase footing size to increase passive pressure  Connect to adjacent footings with deep tie beams for same  Improve soil behind the footing to increase passive pressure 61 Soil Improvement  Soil Improvement  Methods depend on type of soil – get expert advice  For coarse sand and gravel.E. compaction grouting  Excellent source of info: www.com 62 FEMA 547 31 . chemical grout injection (better penetration than cement but more $)  For other soils. P.haywardbaker.
Alexander Newman. P. no heave 63 Hayward Baker. 32 . Soil Improvement  Chemical Grout Injection  Permeation of sands with fluid grouts to produce sandstone-like masses to carry loads. Cont’d  Grout injected in clean sand at regular patterns below footing  May require holes through floor slab (disruption) 64 Hayward Baker. Inc. Polyurethanes …  Gel sets in 1-3 hrs  Usually. Acrylamides. forms composite material with higher soil strength (200-300 psi possible)  Grouts: Sodium silicates. Inc. Grout mixes with sand. Acrylates.E. Soil Improvement  Chemical Grouting.
La Crosse. DL may be OK). Cont’d  Proper confinement stress req’d to prevent heave (soil + found. Inc. duct banks… 65 Hayward Baker.E. Inc.Alexander Newman. 33 . P. Soil Improvement  Example: Chemical Grouting at Trane Company Manufacturing Facility.  Cannot be done near the surface – may blow off the soil  Take precautions not to fill adjacent cracked sewers. WI  Problem: Addition to an existing manufacturing facility building would significantly increase foundation bearing pressure  Solution: Chemical grouting (sodium silicate) to consolidate clean sandy soils beneath the footings to increase allowable bearing capacity and distribute new foundation loading 66 Hayward Baker. Soil Improvement  Chemical Grouting.
Section Showing Zone Of Stabilized Soil Beneath Footing Soil Improvement  Example: Chemical Grouting. Inc. 34 . Cont’d 68 Grouting Operations Underway Showing Grout Pipe Locations and Chemical Grout Storage Tanker Hayward Baker. Soil Improvement  Example: Chemical Grouting. Cont’d Installation of sleeve port (Tam) grout pipes (with holes in sides) using portable drilling equipment (Another method of grouting: Pump and withdraw) 67 Hayward Baker. P. Inc.Alexander Newman.E.
E. but grout displaces soil rather than mixes with it.  Some overburden stress req’d  Can act as both a column and a soilimprovement system. which displace & densify the soil under. A very viscous and stiff (0-3” slump) sitemixed grout is pumped in stages. P.  Widely used to underpin historic structures. 69 Soil Improvement  Jet Grouting  High-velocity injection of fluids erodes soil. replaces it with interconnected soilcrete columns 3-4’ dia. clays more difficult 70 Hayward Baker. 35 .  Gravels and sands easiest to erode. (strength > 1000 psi). to chemical. Inc.Alexander Newman. Hayward Baker. forming grout bulbs. Inc. Soil Improvement  Compaction Grouting  Sim.
72 Hayward Baker. Soil Improvement  Jet Grouting Systems  Single Fluid Jet Grouting (Soilcrete S) – best for cohesionless soils  Double Fluid Jet Grouting (Soilcrete D): Grout jet shrouded with air for more efficient erosion in cohesive soils. generally a design compressive strength or shear strength and/or permeability.E. P. Soil Improvement  Soil Mixing (“Deep Mixing Method”)  Mechanical blending of the in situ soil with cementitious materials (reagent binder) using a hollow stem auger and paddle arrangement to achieve improved character. 71 Hayward Baker.Alexander Newman. Inc.  Triple Fluid Jet Grouting (Soilcrete T): Grout. Most effective system for cohesive soils. air and water are pumped through different lines. yielding higher quality soilcrete. 36 . Inc.
rotation of retaining walls on 3 sides…~$300K of studies and repairs  Replaced with PT framing on caissons bypassing the fill 73 Source: ENR. Natick.Alexander Newman.  400 x 120 ft 2-deck precast structure was built into the side of a hill on uncompacted fill  A decade of problems: Subsidence.E. 1997. Building Replacement is Best  A case of Westin La Paloma parking garage in Phoenix. P. MA (508) 652-8500 anewman@exponent. Q&A Alexander Newman. PE Exponent Failure Analysis Associates.  In Some Cases. August 4. 17. p.com 74 37 . cracking.
Sept. Structural I Exam P.Alexander Newman.E.org/ASCEWebSite/WEBINAR/ListWebinarDetail.. Three review courses are offered : P. P. Fall 2010 ASCE's live P.E.. Sept.. Oct. For more information and registration visit http://www.asce.E. 23 Mon.E. 13 Mon. Sept. Environmental Exam Review Course Dates Course Topics Mon. In addition.E. Aug. Live P.E. Aug.aspx?id=89 75 P. Exam Review Courses on the web will assist ASCE members and other civil engineers in preparing for the P. 20 Mon. Pay a single site registration fee and an unlimited number of people in your organization can attend at that site. 4 Air Quality Waste Water Treatment Hazardous Waste Storm Water Environment Assessment Water Resources For more information and registration visit https://secure.org/Content.E. Civil Exam Environmental Exam P. 30 Mon. Exam Review Courses. 27 Mon..asce. a special Seismic Review webinar is available. Exams..aspx?ProdId=16629 76 38 ..E.
Sept. Sept. Sept. 7 Thursday.aspx?ProdId=16627 78 39 .aspx?ProdId=16626 77 P. Aug. Civil Exam Review. Aug. Sept. Aug.asce.. Sept. 1 Wed. Sept. P. 12-Part Series Course Dates Course Topics Tuesday. Sept. Sept.asce. 8 Wed. 28 Thursday. 9 Tuesday. Sept. 14 Thursday. P. Sept. 15 Wed. Sept.E. 26 Tuesday. E. we will present a Seismic Review course on August 18.org/ASCEWebSite/WEBINAR/ListWebinarDetail. 24 Thursday. Aug. Structural I Exam Course Dates Wed. 22 Wed.. 29 Course Topics Structural Analysis Masonry Design Concrete Design Steel Design Timber Design Bridge Design In addition. 21 Thursday. 30 Structural Analysis Strength of Materials Geometric Design Concrete Design Soil Mechanics Foundation Engineering Hydraulics Hydrology Steel Design Waste & Water Treatment Construction Materials Construction Management For more information and registration visit https://secure..Alexander Newman.. Sept.E. 25 Wed. 23 Tuesday.. 16 Tuesday. 2 Tuesday.org/ASCEWebSite/WEBINAR/ListWebinarDetail. For more information and registration visit https://secure.. Sept. Sept. 31 Thursday.
.org/ASCEWebSite/WEBINAR/ListWebinarDetail. Three Depth Sessions Course Dates Course Topics Tue.Alexander Newman. 5 Wed. Oct.E. E. Civil Exam Review. P. 7 Water Resources For more information and registration visit https://secure. Oct. P.aspx?ProdId=16632 79 40 ..asce. Oct.. 6 Traffic Engineering Geotechnical Thru.

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