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Jan 1, 2002

By Emöke Imre

A point-symmetrical linear coupled consolidation model with displacement boundary condition is suggested for the description of the consolidation around the pile tip after pile penetration. Analytical solution is given. Main features of the solutions are predicted by the analysis of the system of differential equations and, the boundary conditions.

Jan 1, 2002

By Ramin Motamed, Fahim M. Bhuiyan, Raj V. Siddharthan, Joseph Toth

The difficulty in material characterization and the erratic response of cemented soil layers, such as caliche in the Las Vegas valley, creates challenges for practicing engineers to reliably predict the response of deep foundations. The focus of this paper is the numerical prediction of axial response in drilled shaft foundations, which are commonly used in infrastructure projects (i.e., bridges and tall buildings) in Las Vegas, NV. The prevalence of hard caliche layers with variation in the degree of cementation add to the complication in numerical modeling. In this study, the applicability of two existing t-z models, developed for Florida limestone and soft rock, was evaluated based on numerical simulations of three bi-directional load tests conducted at caliche-dominant sites. The corresponding top-down load tests were also simulated for further assessment. A MATLAB-based finite-difference program, NVShaft, has been used to implement the mentioned t-z models in axial load analysis. Complexity originating from drilled shaft construction and the interaction with caliche during one axial load test resulted in a stiffer predicted response compared to measure data. For the other two load tests, both t-z models produced comparable load-displacement responses. It was observed that the t-z model for Florida limestone predicted relatively stiffer responses and higher drilled shaft capacity.

Sep 8, 2021

By N. Shariatmadari

In recent years, determining bearing capacity of piles from in-situ testing data as a complement of static and dynamic analysis has been used by geotechnical engineers. In this paper, different approaches for estimating base bearing capacity of piles from SPT data has been compared and evaluated. A new method for pile base bearing capacity in sand is proposed using SPT records. Data averaging, failure zone extension, and plunging failure of piles have been addressed in the proposed approach. A data bank comprising 10 full scale static load tests on instrumented piles and 26 dynamic tests, analyzed with signal matching technique by CAPWAP software, was used for validation. The SPT data that was performed close to pile locations is also included in the data base. Comparison of current methods by error investigation with Log-Normal approach demonstrates that the proposed method predicts pile base capacity with more accuracy and less scatter in comparison to other methods.

Jan 1, 2006

By Dean E. Harris

The realignment of U.S. Highway 95 in Sandpoint, Idaho, is being designed on a site underlain by glaciolacustrine soil that includes very thick deposits of soft, sensitive clay to estimated depths of greater than 200 m. The highway realignment will include construction of numerous embankments, mechanically stabilized earth (MSE) retaining walls, and pile-supported bridges. The area of the proposed new highway corridor also includes existing historic and commercial buildings, a railroad, sensitive environmental areas, and economically vital tourism/recreational assets. The evaluation of pile axial capacity included the use of a variety of methods, including total stress, effective stress, and empirical methods using the results of piezocone soundings and conventional borehole and laboratory tests. These methods were used along with the findings from an instrumented static loading test to design the piled foundations for the bridges. A critical factor throughout the design of the pile foundations was controlling settlements to levels that could be tolerated by the bridges. Also, because of the proximity of the pile foundations to the existing structures and the proposed new embankments, the project has required careful consideration of the potential interaction between these elements. The analysis of piles also considered the potential for settlement of embankments, drag loads on the piles, and downdrag.

Jan 1, 2003

By T. Jason Hardell

The Victory Bridge project was contracted by the New Jersey Department of Transportation. The project included the construction of two 4000-ft precast segmental concrete bridges to replace the existing Victory Bridge that was built in the 1920's. The existing bridge was a swing span bridge that was in desperate need of replacement. The project was considered high priority due to the large maintenance costs to keep the swing span operating over the busy navigational channel. In March of 2003 construction began on the first bridge and by April of 2005 all of the segments were set for the second bridge. On September 5 of 2005 the second bridge was open to traffic. The total cost of the project was $110-million. The two new bridges required the construction of 24-eight foot and 32-six foot diameter-drilled shafts with rock sockets. All of the shafts were constructed in the tidal Raritan River working from barges. What will follow is a description of the construction techniques that were used to build these drilled shafts, the anticipated and unanticipated challenges that were encountered during the project, and the lessons learned.

Jan 1, 2005

By Emad Farouz, Ehab S. Shatnawi

"The increasing demand for small deformations and high-capacity drilled shafts without enlarging drilledshaft diameters has motivated the development and increasing use of a base grouting (BG) technique. This technique has been demonstrated to improve drilled-shaft capacity, especially for shafts tipped into loose cohesionless soils. Nevertheless, there remains considerable uncertainty in predicting the performance of base-grouted shafts, particularly for shafts tipped into cohesive soils. To date, there are only two documented design methods for estimating the axial geotechnical resistance of base-grouted shafts: Tip Capacity Multiplier (TCM) and Axial Capacity Multiplier (ACM) methods. A comprehensive test program was carried out during the design phase of the Wisconsin Zoo Interchange project to help optimize the flyover ramp’s foundation design. The test program included installing and testing one base grouted shaft and one ungrouted shaft at two sites with different ground conditions. Based on test results, it was concluded that prediction of the TCM method is well correlated with the measured values for both cohesive and granular soils; however, both methods tend to underestimate the axial resistance. Results also highlighted the importance of the base-grouting criteria in taking full advantage of the base grouting.INTRODUCTIONBase-grouted drilled shafts (BGDS), also known as post-grouted drilled shafts, consist of conventionally installed drilled shafts that contain access grout tubes placed within the shaft during construction. After installing the drilled shaft and achieving the pre-established concrete strength, grout is injected at the shaft tip through the access grout tubes to improve soil behavior around the drilled-shaft base. The tip grout injection improves the overall shaft capacity and reduces settlement through Densifying the in situ soils, compressing any debris left by the drilling process, preloading the soil beneath the tip to mobilize the shaft base resistance within service limits, increasing the tip area, and increasing the side resistance in the lower portion of the shaft."

Jan 1, 2016

By Francis D. Leathers

Four friction pile load test programs, including 23 tension tests and 9 compression tests, have been performed as part of the Central Artery/Tunnel Project in Boston, Massachusetts. The tests, performed on both precast, prestressed concrete (PPC) piles and steel piles, yielded the following adhesion values: [Soil Type Clay Clay Glacial Till Interbedded Sand and Clay Interbedded Sand and Clay Pile Type PPC Steel Steel Steel PPC Adhesion (psf) 610 to 1,200 230 to 900 220 to 550 680 1,280 ] The adhesion appears to be affected by differences in pile material type, with PPC piles having higher adhesion than steel piles. However, part of the apparent difference for the clay may be due to differences in time between driving and testing. The significant range of test data means that the need for site specific testing to determine or verify design values of adhesion should be considered during design. Creep rates at loads near failure ranged from about 0.02 to 0.18 inches per log cycle of time, with most values in the range of about 0.04 to 0.08 inches per log cycle of time.

Jan 1, 1994

By Jason Buenker, Molly Winston

Torque-installed piles are gaining popularity in Southern California as the go-to deep foundation element for small- to medium-capacity loads in urban environments. The torque-installed pile is a displacement- based screwed pipe pile with a closed-end conical tip welded to the bottom of the pipe. Torque-installed piles are most efficient in loose to medium dense soils with high liquefaction potential. Where used properly, torque-installed piles can be installed faster, require less clean-up, and create less onsite vibration/disturbance than other pile alternatives. However, torque-installed piles are not applicable in all soil conditions and care must be used to apply the pile effectively in the correct subsurface environment. This paper will review current Southern California state-of-the-practice for torque-installed pile design and construction, potential roadblocks to successful installation, and available capacities from load tests. INTRODUCTION Torque-installed piles are a type of full-displacement screwed pipe pile originally developed in Southern California circa 2001 by Substructure Support, Inc. The pile is unique for its proprietary closed-end conical tip shown in Fig. 1. The tip has a welded steel-helix plate and cutter teeth that allow the pile to be advanced efficiently under applied torque and down pressure (crowd). Since original development of the pile, several contractors or manufacturers have proposed similar proprietary screw-type piles with comparable conical tips. Pile installation is relatively quiet, vibration-free, does not generate spoils, and faster than comparable pile types. The pile was originally developed as an alternative to driven pile foundations and remains a critical substitute to driven foundations in urban environments. Torque-installed piles are conventionally specified as 12 ¾-inch outside diameter (OD) steel pipes with a ⅜-inch-thick wall, although larger sizes with alternative dimensions have been used outside Southern California. Pile installation lengths generally range from 30 to 50 feet but may reach 80 feet or greater where soil conditions permit. The pile is generally backfilled with concrete following installation to increase lateral pile stiffness and may incorporate rebar cages or other reinforcing steel to facilitate connections to structural elements. The pile is frequently specified using performance-based specifications that encourage contractor innovation and use of proprietary installation means and methods.

Jan 1, 2019

By Richard W. Hanford

The geotechnical construction industry generally considers soil mixing to be defined as an in situ ground improvement or treatment method by which a dry or wet reagent is introduced into the ground and is blended with the soil by mechanical or rotary mixing tools. This results in relatively homogenous mixtures whose engineering properties are improved and are greater than the soil properties before mixing. Reagents usually include cement, but may also include processed clay such as bentonite, when a reduction in hydraulic conductivity is desired, or other proprietary chemicals when chemical stabilization is the objective. Mixing may be either shallow or deep. Shallow Mixing is the term arbitrarily used for treatment of soils within the upper 30 feet; Deep Mixing denotes treatment below 30 feet to the depth limits of the equipment. Mixing equipment may consist of single or multiple-shaft tools having cutting and mixing blades of many different configurations. To avoid using proprietary nomenclature, reference to Shallow Mixing Methods (SMM) and Deep Mixing Methods (DMM) are the preferred terms. Although originally developed and patented in the United States in 1956, in situ construction using various soil mixing methods is more prevalent in Japan and the Scandinavian countries. Reintroduced into the United States from Japan in 1986 for ground improvement and liquefaction mitigation at Jackson Lake Dam, Wyoming, acceptance of soil mixing methods has been gradual but slow. Applications typically include:

Jan 1, 2001

By Clyde N. Baker

The paper describes procedures used to predict the settlement performance of drilled shafts constructed under slurry through water bearing deposits to a dense bearing strata, considering both side resistance and end bearing. A full scale instrumented drilled shaft load test on a Jersey City, New Jersey highrise project is used as a case history to compare with prediction.

Jan 1, 1991

By Per Eriksson

For light buildings on clay, foundations on L/C-columns is in many cases a competitive alternative to piles when the thickness of the clay is moderate (<20 m). The method is applicable for the above mentioned depth when the clay is normally consolidated, and for thicker deposits when the clay is overconsolidated at depth. This case study concerns a shopping mall in Nordby, Sweden, founded on L/C-columns (5-15 m in length) and generally spaced 1.45-2.0 m (spacing 0.7 m was used below pillars). The base slab was built as a raft foundation, using fibre reinforced concrete.

Jan 1, 2000

By Sam Yao, Ali Naeem, Sara Barrett

Brooklyn Basin Project is a multi-billion-dollar development of the former Port of Oakland 9th Avenue Terminal located along the Oakland Estuary of California. A centerpiece of the development is the 10-acre shoreline park which will be built on a 1,200 ft long by 225 ft wide historic wharf. The wharf was built in the 1930’s on concrete and timber piles with a flat concrete slab. Prior to constructing the wharf, a rock dike was placed to protect the shoreline. The presence of the rock dike increased the hazards from lateral spreading of the underlying bay mud and non-ductile shear failure of piles driven through the dike. To open the park to the public, the wharf required a seismic retrofit in compliance with the California Building Code. The paper presents the results and conclusions of the following topics: • Structural condition assessment and repair strategies for the existing wharf deck, piles and jackets • Application of the California Building Code (CBC Ch31F) for the performance-based seismic evaluation of existing piers and wharves • Nonlinear pushover analysis of the wharf including the combination of inertial and kinematic effects • Impact of rock dike on lateral spreading and kinematic effects and the significance of existing piles in stabilizing the lateral spreading of the rock dike • Retrofit strategies for the wharf to meet the required seismic performance requirements per the California Building Code and reduce the demands on existing piles which were driven through the rock dike INTRODUCTION The 65-acre Brooklyn Basin Development project is located in Oakland, California. The project consists of 3,100 housing units, 200,000 sq. ft of retail and commercial space, along with various parks and public access improvements along the Oakland Estuary. A centerpiece of the development is the 10-acre Shoreline Park which will be built on a 1,200 ft long by 225 ft wide historic wharf. The wharf was built in the 1930’s on concrete and timber piles with a flat concrete slab. As shown in Figure 1, the wharf deck and piles support the 9th Avenue Terminal Building.

Jan 1, 2018

By Marco Fellin, Van E. Komurka

Significant cost and construction benefits were obtained from performing a bi-directional static load test prior to construction on the Russell Street Bridge Replacement project in Missoula, Montana. The project utilized 24 drilled shafts to support two three-span bridges across the Clark Fork River. A bi-directional static load test (“BDSLT”) was performed on a large-diameter production shaft to demonstrate construction methods and confirm design assumptions. Subsurface conditions consisted of gravel with sand to a depth of 20 feet (6.1 m), underlain by gravel with sand, silt, cobbles, and occasional boulders. The test shaft had a nominal diameter of 5.9 feet (1.8 m), and an embedded length of 75.5 feet (23.0 m). The geotechnical engineer of record and the BDSLT test engineer collaborated to optimize the BDSLT jack assembly location within the test shaft, determine appropriate instrumentation locations, and plan the test protocol. The maximum applied test load was 10,707 kips (47.6 kN). Significant benefits were obtained from performing the BDSLT test, including 1) reducing each production shaft’s length by using a higher LRFD resistance factor allowed by having performed the testing, 2) using test-determined unit shaft resistances to evaluate and accept two production shafts that may have otherwise required remediation, and 3) providing the Montana Department of Transportation (and other designers) with increased presumptive unit resistance values in the gravel/cobble/boulder deposits. PROJECT DESCRIPTION The project was constructed in Missoula, Montana for the Montana Department of Transportation (“MDT”). The original bridge was approximately 60 years old, and consisted of a two-lane, 420-foot-long (128-m), four-span, riveted steel plate girder design spanning the Clark Fork River. The bridge was due for replacement owing to its deteriorated state, and the need for increased traffic volume capability afforded by a four-lane structure. HDR was the structural engineer. The preferred bridge alternate was a 459-foot- long (140-m), three-span, welded steel plate girder design. The new bridge was designed to meet current standards in accordance with MDT bridge design and AASHTO LRFD criteria. The new bridge was constructed in phases to keep traffic open during construction.

Jan 1, 2019

By Scott A. Walker, Roberto A. Lopez, Lori A. Simpson, David A. Shook

500 Folsom Street is part of the new Transbay neighborhood in San Francisco, which is being redeveloped after the 1989 Loma Prieta Earthquake damaged a freeway viaduct; removal of the viaduct created parcels of land available for development. The development consists of a 42-story residential tower with a six-level basement. The slender, core-only structure was designed using performance-based seismic design. Subsurface conditions include undocumented fill, Dune sand, marsh deposits, sand, and clay, all overlying sloping bedrock of the Franciscan Formation. The building is supported on a 10-foot-thick mat foundation approximately 62 to 72 feet below street grades; clay, sand, and bedrock are all present at mat subgrade. Under a portion of the mat, sand susceptible to liquefaction was present. The variable subgrade conditions and potential for ground failure, along with the depth of mat subgrade below street grade, created a challenge for the design and construction team to solve. The ground below mat subgrade needed to be improved to mitigate the liquefaction potential and provide more uniform support. The areal extent and depth of ground improvement necessary to support the mat with an acceptable amount of deformation was determined. Settlement was analyzed and subgrade moduli were provided for design of the mat, with multiple iterations performed to converge between the geotechnical and structural models. Based on the project schedule and logistics, it was beneficial to work from street grade to improve the ground. In order to target the depths below the mat and minimize wasted effort and materials within the depth of excavation, grids of jet grouting were determined to be the most economical ground improvement method; however, it was challenging to install the columns from 65 feet above the top of the target zone. During installation, QA/QC was performed to check that the jet-grouted columns were installed to the design depth and diameter and developed the design strength.

Jan 1, 2018

By John Lemke

Current practice for monitoring static pile load tests commonly consists of measuring load and displacement at the top of a pile. This is typically accomplished by monitoring dial gauge movements, line pressure of a hydraulic jacking system, and electronic load cells on occasion. While this testing approach provides useful information for one boundary condition (the top of the pile), a system that measures movement and/or strain along the entire length of the pile can provide additional useful data that can be used to refine pile design. Automated data acquisition systems provide the essential ingredient that can integrate these types of sophisticated instrumentation devices into a standard pile load test program in a cost effective way. This paper provides a general overview of pile testing instrumentation and describes a newly developed chain of instrumentation modules that can be embedded in a pile to gather additional testing information. The new system can measure forces and movements within the test pile synchronously with measurements at the pile top, and the direct application of this system to axial and lateral pile testing is illustrated. This is particularly relevant to the design of ACIP and drilled displacement piles since determination of the reinforcement cage length is important from the standpoint of both seismic design and foundation cost.

Jan 1, 2002

By V. M. Troughton

Further pile load testing has been carried out at Canary Wharf to compare the performance of base grouted and ungrouted bored piles founded in the Thanet Sand. The testing regime included three preliminary test piles and two working test piles. The results of these tests are summarised in Table 1 below. Two of the preliminary test piles were located only 14m apart to compare the performance of a base grouted and ungrouted pile in similar ground conditions. The load/settlement behaviour of these two preliminary test piles are compared on Figure 1. All the piles were drilled under bentonite with a drilling bucket. In the base grouted piles four grouting tubes were placed with the reinforcement cage to within 500mm of the pile toe. After the pile had been concreted these grouting tubes were then extended to the pile base by drilling and packers were installed. Grout was then injected into the four tubes simultaneously.

Jan 1, 1991

By Rajesh Minda

160 numbers of double bulb underreamed piles were constructed based on the safe loads specified in IS code at Tripura. The pile load tests yielded a much lower capacity. A detailed investigation work was carried out to find out the reasons for anomaly. The work included soil exploration followed by extraction of two piles bearing numbers 72 and 151. It was seen that the bulbs were not formed as per specification. Some comments on IS Code have been made at the end.

Jan 1, 1996

By Haoran Zhang, Chu Ho

A recent design-build project in New York involved various degrees of additions and improvements to four existing transit stations. Reuse of the existing foundations was considered a more sustainable alternative than constructing new foundations for the project. This approach mitigated the extent of demolition work and limited the amount of downtime for track operations. A key challenge for reusing the existing foundations was the lack of as-built drawings. In order to obtain some measure of confidence for the proposed foundation reuse, non-destructive investigation technology was adopted to evaluate the structural integrity of the piers and foundations. A total of 47 piers for the existing passenger platform were investigated for possible reuse. Several test pits, excavated to verify the foundation type and configuration, indicated the piers were founded on a combination of shallow footings and drilled shafts. Pile integrity tests were performed to verify the length of the drilled shafts. Geotechnical capacity of drilled shafts was evaluated for side friction and end bearing resistance, and confirmed using a proof load test conducted from the existing platform structure. This paper presents the investigation methodology and discusses the approach adopted for geotechnical design of the existing foundations for reuse.

Sep 8, 2021

By Axel J. Pollak

Since the late 1960&apos;s the Interstate Division for Baltimore City (IDBC) has been planning and developing the Interstate Highway System for the city to meet regional planning goals. The principal goals are to provide convenient access to the central business district and the port while diverting through traffic away from these congested areas. Interstate Route 95, an eight-lane highway carrying north-south traffic, has headed the city&apos;s priority list; during the 1970&apos;s its construction proceeded steadily from both east and west towards the harbor. Closing the final 8800-ft (2670-m) gap under the harbor will complete Interstate 95&apos;s construction. This final portion, known as the Ft. McHenry Tunnel project, will be built in nine construction contracts. Construction costs of the complete project are expected to exceed $700 million, making it the costliest single project in the Interstate Highway System. Full funding is being provided initially by the Federal Highway Administration (FHWA), and the Maryland Department of Transportation will re-pay the 10 percent local share from toll receipts within the first three years of operation.

Jan 1, 1989