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By Florian König

It is well known that the bearing capacity and stiffness of displacement piles may increase significantly with time, a phenomenon usually referred to as set-up. In cohesive soils the set-up is commonly explained by consolidation processes in which the dissipation of the excess pore pressures around the pile leads to an increase in effective radial stresses. Recent case histories show that set-up may also occur in sand over a period which exceeds by far the consolidation process. Therefore, other effects apart from the dissipation of excess pore pressures must contribute to this long-term set-up effect. This paper presents the results of a series of multiple pile load tests on prefabricated concrete piles which capture the effect of pile set-up empirically. The main characteristics of the set-up trend are shown with respect to soil type, pile dimensions and distribution over the pile length. Possible reasons for pile set-up like consolidation and stress relaxation after the end of driving are examined using a finite element model which simulates the pile installation process.

Jan 1, 2006

By Michael D. Justason

"In January 2009, long-time competitors, Anchor Shoring & Caissons Ltd. of Toronto and Bermingham Foundation Solutions of Hamilton, joined forces to tackle one of the Greater Toronto area’s largest deep foundation projects: the West Toronto Diamond Rail Grade Separation. The two companies formed the “West Diamond JV” and succeeded in winning the contract from the Canadian National Railways. This deep foundations work was the first and most significant part of the $300-million-plus rail grade separation project. A big part of the job turned out to be dealing with local government regulations and citizens’ concerns with noise and vibration.The project is approximately 10 km (6 mi) northwest of downtown Toronto in an area of mixed-zoning including light industrial, commercial and residential buildings. The area is commonly called the “The Junction,” because of the heavy rail- traffic. The “West Toronto Diamond” refers more specifically to the railway junction where the North-South tracks of Canadian National (CN) Railway meet at a level crossing with the East-West tracks of the Canadian Pacific (CP) Railway. The goal for this part of the project was to convert the West Toronto Diamond into a grade-separated junction by depressing the CN lines under the CP lines, thus allowing commuter rail carrier, called GO Transit, intercity carrier VIA Rail, and CN freight trains to pass through the new underpass.Dawn Tattle, president of Anchor Shoring & Caissons says, “not only is the site in a densely populated area adjacent to homes and businesses, the crews worked adjacent to active rail lines with numerous trains passing daily. During the 7-hour working day, approximately 60 trains passed through the site in very close proximity to working crews.” Safety was paramount. While trains were passing through the site, it was a railroad requirement that all equipment and men stop working. In addition, at those times, all personnel were required to stay 6 m (20 ft) from the tracks and were required to face the tracks. For the faster commuter trains, this work interruption could last as little as 2-3 minutes, while interruptions caused by the slower freight trains could last as long as 25 minutes. The most disruption to the site occurred during the morning commute between 7 to 9 a.m., so work did not really get underway until after that time. Once work finally commenced the race was on to finish as much as possible before the afternoon commute – hence the shortened work day. The amount of disruption caused by the trains was a big unknown faced by the JV going into the project, but crews adapted quickly to the very unusual work environment"

Jan 1, 2012

By Dennis Nottingham

Increased interest in seismic soil liquefaction and preventative soil stabilization sets the stage for improved deep compaction methods using pile driving techniques. In 1971 L.B. Foster Company personnel patented a method of deep compaction using a vibratory pile hammer and pile probe. The technique had some success, but did not produce consistent results and thus found its way to obscurity. Other patents attempted to modify the technique by various probe modifications, but again without measurable improvement from a practical point of view. Solutions to economical deep compaction up to 100-foot depths particularly in saturated granular soils would have a great impact on the construction industry and new bulkhead structures being developed, thus PND was prompted into related research and development. The advent of higher horsepower vibratory hammers, coupled with PND engineers' experiments, observations and measurements, led to an "H" pile probe design which has produced measured soil density improvements up to 250% using SPT "N60" values as a measure. Case histories of two projects involving extensive SPT soil sampling comparative measurements will be discussed along with findings that led to the compaction success. Applications to numerous modern "Open Cell" bulkhead projects will be presented and discussed.

Jan 1, 2004

By Dr. Anup Kumar Mandal, Partha Roy, Shuvranshu Kumar Rout, Dipak Mandal, Biswajit Das

Installation of a new scalping station with bunker, apron feeder, scalping screen, ramp -retaining wall and approach bridge was planned in an existing integrated complex of phosphate fertilizer at a remote place in West Africa. Rock phosphate ROM, transported from mines by a combination of 100 Ton and 150 Ton dumper, would be fed to a steel bunker having capacity of 180 m3. Different options were studied for retaining wall at the junction of ramp and approach bridge. Initially options with conventional RCC Retaining Wall, Gravity Retaining Wall with Precast Concrete Blocks and Reinforced Earth walls were studied. Option with Reinforced Earth was selected as this option was much more cost effective compared to other options. But real engineering challenges cropped up when competent execution contractors were not available nearby the site. To minimize the cost, an innovative option with Stepped Retaining wall was then studied. Geotechnical parameters of native soils, selected for the construction of the approach ramp were determined and it was found that with available poor geotechnical parameters of the native soils, design of stepped retaining wall would not be feasible with respect to available bearing capacity, subjected dead load, live load, operational load and earth pressure. A conscious effort was then made to make the design feasible by improving the geotechnical parameters of the retained earth of ramp near the retaining wall. In view of that, mix design with locally available materials like Silexite, Sand, Laterite, Gravel and Silt at different proportions was made and samples were tested in the laboratory to determine relevant geotechnical parameters. Based on the test results, a suitable mix was selected that had high shear strength, enhanced bearing capacity and improved coefficient of earth pressures. Design of stepped retaining wall was then made with the selected construction materials and construction completed. The plant was successfully commissioned in December. 2021.

Sep 1, 2022

By K. Viking

It's well known that conventional impact hammers, usually are the method to use in order to drive precast prestressed concrete piles. However sometimes the vibratory technique might be considered as a suitable alternative due to favourable soil conditions. It is also well known that piles driven into granular soils can be installed more efficiently by the use of a vibratory driver compared with impact hammers. However, the use of the vibratory technique is seldom regarded as the first choice, since the technique is constrained by several uncertainties related to the pile capacity, and concrete piles to cope with tensile stresses. With the opportunities of having suitable subsurface conditions and a fair amount of piles to be installed, it was anticipated that the use of the vibratory method could result in a significant reduction of the installation costs. Part of the uncertainties of using a vibrator was intended to be eliminated by restriking the vibratory driven pile with an impact hammer and use a Pile Driving Analyzer? (PDA) to correlate recordings of soil resistance to driving with measured rate of penetration, and to evaluate the static capacity and load/settlement characteristics of the vibratory driven pile by conducting static load test. The conducted test study of using a vibrator to drive the precast prestressed test pile (14-in. square by 30-ft-long) did not turn out to the author's complete satisfaction. The present paper focuses mainly on a numerous practical engineering issues in relation to the use of the vibro-technique to drive precast prestressed concrete piles in granular soils. The obtained experiences of using a PDA to monitor vibro-driven piles, with its potential and limitations, is presented and discussed. Furthermore, a simple method of how to subjectively pre-estimate the soil resistance due to vibratory driving is presented and discussed. The reasons for the partly unsuccessful test study are discussed in great detail based on the obtained experiences. Suggestions of how to better approach a similar situation in the future are also provided in great detail

Jan 1, 2004

By Mohab Sabry, Emre Biringen

"Over the past decades, there has been an increasing recognition of the strategic use of pile-supported rafts in design of heavily-loaded structures to reduce total and differential settlements. However, such a hybrid foundation construction method has not been widely utilized in many countries, including the U.S., due to code limitations. In current practice, the foundation design is based on either (i) the bearing capacity of the raft supported by the subgrade soils, or (ii) solely the pile capacity. This paper addresses the potential use of such hybrid piled-raft systems, where the structural load is shared by both by the piles and the subgrade soils directly beneath the raft, in foundation design of power plant structures. The study assessed some of the characteristics of piled-raft behavior by undertaking three-dimensional finite element analyses of two raft sizes, and various pile layout patterns, including the rafts with piles distributed evenly and only in the central area of the raft. The computer software PLAXIS 3D with the Mohr-Coulomb constitutive soil model was used to facilitate the modeling of such cases. The results presented in this paper indicate how strategically locating the piles could reduce the differential and total settlements.INTRODUCTIONUnder the high applied loads coming from the superstructure, the addition of piles is primarily required to improve the factor of safety against failure when a raft does not provide adequate bearing capacity. If the bearing capacity of the raft is sufficient to carry the total load with a reasonable safety margin, then the addition of piles is usually intended to reduce the settlements to an acceptable amount. In current practice, the design process for pile-supported raft foundations conservatively concentrates on providing solely the pile capacity to carry the total structural load without taking the contribution of the raft into account. This paper addresses the potential use of hybrid piled-rafts in controlling foundation settlement of power plant structures by considering the support of both the piles and the subgrade soils beneath the raft to carry the load."

Jan 1, 2017

By Brad W. Taylor

"During the past several months, I have introduced to civil and structural engineers an innovative solution for the integrity testing of concrete using the Thermal Integrity Profiler (TIP) Wire Cable System by Pile Dynamics. While in the process of “educating” highly-trained professionals about a technological breakthrough, I ended up being educated myself about their needs for quality control/quality assurance (QA/QC). With that in mind, I would like to focus on their two key areas of concern:• How complex is the TIP installation process?• How does the QA/QC engineereffectively analyze and report TIP test results?A few months ago, during a discussion with a senior QA engineer, he asked a question that stopped me in my tracks: “Why should we do foundation testing at all?” Turning it around, I asked, “Why wouldn’t QA/QC personnel want to know everything they could about their critical infrastructure foundation?” Honestly, I didn’t answer his question nor did I fully comprehend what he was trying to say. With his experience, the engineer understood that there has not been an integrity test or a combination of integrity tests that could deliver an inside the cage and outside the cage (cover) complete data set that would provide a definitive profile of the entire shaft. Crosshole sonic logging (CSL) becomes more effective the larger the diameter of the shaft becomes, with a maximum effectiveness between 70% and 80%, but does not provide any data of the integrity of the shaft beyond a straight line between CSL tubes. Gamma-gamma logging (GGL) provides qualitative information about the concrete surrounding the GGL tube and device, and it provides information about a small percentage of the drilled shaft concrete near its outside edge."

Jan 1, 2017

By Hajialilue Bonab M.

The soil-pile interaction under lateral impact loads is not yet completely well known. Many tests on single piles under static lateral loads in centrifuge have been performed and P-y curves have been determined at different levels of the pile in soil. Following these static tests on piles, a large program is undertaken with the same piles submitted to impact loads. The pile equipped with various pile caps has been impacted under variable amplitudes of shock. The behavior of the pile under different impacts was studied and dynamic parameters of the soil-pile system have been determined. Many cases of loading constituting various load histories have been analyzed. They are resulting from parametric centrifuge tests run out, on the one hand with constant and cumulative impacts and on the other hand, variable and cumulative ones. The Influence of each type of loading was studied. Using a finite element method, a non-linear pile-soil system was conceived and a transient dynamic analysis have been performed. The results of the non-linear analysis and experimental data were compared giving a good agreement.

Jan 1, 2002

By Djk Arentsen

A new technique to drive tubular piles by impact hammer inside the pile has confirmed a dramatic reduction of noise and the opportunity to save steel. Also a reduction in driving time and a higher bearing capacity has been observed during a test program of this technique. As part of the so-called "Down-the-hole" driving technique, a wave equation analysis has been developed to calculate driveability and pile stress. The main feature of the new "Down-the-hole" technique is the development of a patented device allowing uncoupled penetration of pile tip and pile shaft, which makes it possible to drive both closed or open end piles and reduce the stress level induced in the pile wall. During a test program, a number of instrumented piles were driven and compared with traditional driving of the same pile with the same hammer on top (also instrumented). Also the stresses and performances were compared with precalculations. This paper, explains the technique and presents the test and noise results, in comparison with traditional top-pile-driving. The "Down-the-hole" driving technique is an interesting alternative for special applications where traditional pile driving requires a large wall thickness or in areas where noise is a hot item.

Jan 1, 1996

By Mario Carnevale, Myles Danforth, Michael Oakland

The cost and overall effectiveness of foundation design depends on a robust characterization of the subsurface geologic setting. It is common practice to formulate deep foundation design from subsurface geologic characterization based on boring programs. The confidence level of geologic characterization is directly related to that of geologic interpretations, which are based on the spatial sampling pattern of boreholes relative to the complexity of the geologic setting. This paper presents a case history illustrating issues that arise during pile construction from over-simplified geologic characterization, the challenging steps taken to improve the subsurface geologic model, and the effect of additional characterization efforts on the pile foundation program. The seismic characterization methods used include multi-channel analysis of surface waves (MASW) and seismic refraction.

By David T. Farber

"Stabilization of an existing cellular tower foundation system without dismantling the tower or compromising the existing foundation system was accomplished by installation of a jet grouted pile system. The tower was originally designed to be placed on a steep hillside and to be supported by a mat foundation founded on existing bedrock. The as-built conditions of the tower foundation system showed it to be constructed on a combination of loose fill of varying thickness and native stiff silts and gravel material. To avoid the potential of differential settlement, a jet grouted pile foundation system was installed to the top of bedrock. The jet grouted pile system was rapidly installed over a two-day period so as to not delay operational permitting of the tower.INTRODUCTIONA tri-legged lattice cellular communication tower was constructed on the side of a steep hill located in a mature hard wood forest. Access to the site as well as available work area was limited to small track type drill rigs and equipment. The original tower design required the tower to be supported by a mat foundation bearing directly on bedrock. Based on a review of the foundation construction and results of a subsurface investigation, it was discovered that the foundation was built directly over a loose fill material that varied in thickness from 0 to 4.27 meters (0 to 14-ft). Because of the uncompacted nature and varying thickness of the loose fill materials, the tower would be susceptible to differential settlement which, could lead to tower instability.The objectives of this project included the following:• stabilize the mat foundation against differential settlement without removing the existing tower structure or foundation system• rapidly complete stabilization activities to allow operational permitting of the towerSOIL CONDITIONSThe subsurface soil conditions that the tower mat foundation rested on were evaluated by installing three borings in a row from the inward slope portion of the mat foundation (B-1) to the outward slope portion of the mat foundation (B-3). Figure 1 illustrates the subsurface soil stratigraphy. The three borings encountered the following subsurface conditions:"

Jan 1, 2005

By Joseph T. Coe, Siavash Mahvelati, Philip Asabere

Characterization of existing foundations remains an important issue as foundation reuse and rehabilitation continue to garner increased attention. In the case of unknown foundations, geophysical and nondestructive testing (NDT) methods have been utilized in the past to evaluate foundation geometry and could serve as useful tools in the case of foundation reuse. A comprehensive study was initiated in the late 1990’s and early 2000’s that evaluated the effectiveness of the available geophysical and NDT technologies to characterize unknown foundations for scour evaluation purposes. At the time of that study, the Multichannel Analysis of Surface Waves (MASW) geophysical method was in its infancy and not widely used. Since then, MASW has become increasingly prevalent in geotechnical applications as the method presents a number of potential advantages when characterizing the subsurface, including rapid testing, increased signal to noise ratio, and ability to resolve velocity inversions. This paper presents a case study that explores the abilities of MASW as an unknown foundation characterization tool. MASW was applied to determine subsurface stiffness at a bridge foundation site in the Philadelphia metropolitan area. One MASW survey line was performed immediately over the foundation of interest and another was performed over a control zone adjacent to the foundation to establish a baseline site profile. The purpose of this testing was to examine whether MASW could establish the geometry of the foundation at this site. This paper presents the site conditions and MASW testing procedures, followed by a discussion of data analysis and interpretation.

Jan 1, 2016

By Issa S. Oweis

Two Towers are currently under construction in Central Moscow in the Russian Federation. Building A is a 96 story tower and Building B is a 65 story tower. The columns in both structures bear on a thick concrete mat that is supported on drilled shafts, 1.5 m in diameter. The shafts derive their capacity from weak limestone with layers of marl. Assigned allowable shaft loads were initially based on rock strengths that were later verified by load tests using the Osterberg Cell. One of the load tests was carried to near failure which allowed refining socket friction values that were later used in the design of Building A. All shafts were advanced using an auger and concrete placed in the dry. Grout tubes were placed with the reinforcing cage which allowed grouting of the limestone in contact with the shaft. Load sharing between the shafts and the mat was approximated using published methods as well as site specific finite element analysis. This paper covers the methodology of design, analysis of the Osterberg results to derive non-linear stiffness of the rock and differences between finite element analyses and results by approximate methods.

Jan 1, 2007

By Jiun-Yih Chen

Pile load tests are regularly used to verify pile capacities. Sometimes, they are used to optimize pile designs. This paper presents a case study based on a real project, in which the information obtained from load tests during construction was used to shorten the design pile lengths without a formal decision analysis. In this study, a simple probabilistic model was used to assess the probabilities of failure based on design information. The Bayesian approach was used to update the probabilities given the additional information from load tests. These probabilities were then used in a formal decision analysis to determine the optimal pile lengths based on design information and based on the additional information from load tests. The optimal pile lengths are different from those implemented in the project without a formal decision analysis. The value of the formal decision analysis is illustrated by its ability to optimize the pile length in a transparent and defendable way.

Jan 1, 2009

By A. Partos

It was decided to build a fourteen-storied office building over a six-storied garage and a four-storied office building. The high vertical and horizontal loads required foundations on rock approximately 18m below street level. Drilled piers (caissons) were selected. Eight caissons (1.98m diameter) were installed through the six-storied garage and four caissons from a temporary deck at the location of a former two-storied building. Excavations were done by the slurry method. Proof testing of rock was done before construction by test borings and during construction with a core barrel of small diameter. Quality control measures included telecommunications between ground crews and the equipment operator on the garage roof; records of field observations and testing of bentonite slurry and rock; and a continuous evaluation of all information. Instruments were installed in one caisson to monitor load distributions and curing of concrete.

Jan 1, 2010

By David K. Crapps

The drilled shaft load tests at Port Orange were part of a demonstration project sponsored by the Federal Highway Administration (FHWA) and the Florida Department of Transportation (FDOT). Three load tests were conducted. Test 1 was a conventional test with the test shaft loaded from the top. Test 2 included an Osterberg load cell at the tip and a conventional load test from the top. Test 3 used an Osterberg load cell at the tip of a production drilled shaft. All three test shafts were socketed into limerock and were carried to failure. This paper describes the test program and presents a summary of the test results. Figure 1 presents some photographs of the load test setups and Figure 2 shows the location of the drilled shaft load tests. SITE CONDITIONS The Port Orange Bridge is located on US A1A over the Intercoastal Waterway in Port Orange, Florida (south of Daytona Beach). The new bridge will provide four lanes of traffic with a 65 foot vertical clearance for Intercoastal Waterway traffic. The channel and flanking piers will be supported by 54" drilled shafts socketed into the rock. The bridge is being constructed in two phases. The southern half will be completed first, the old bridge removed and then the northern half will be constructed. The first phase is scheduled to be opened to traffic in October 1989. Each of the four piers near the channel will be supported by 12 drilled shafts with 6 shafts per pier being constructed in each phase.

Jan 1, 1989

By Kyle M. Rollins

To improve our understanding of lateral resistance of pile groups, a series of lateral load tests were performed on a full-scale pile group using both static and dynamic loads. The pile group consisted of nine 0.6 m-diameter steel pipe piles driven into clay. During the static tests, the load was cycled fifteen times to evaluate the drop in lateral resistance that would occur due to repeated loading and the formation of a gap. The peak load typically decreased by about 15% from the initial cycle to the last cycle. The load carried by each pile was also measured and there was a significant drop in resistance for the piles in the trailing row relative to the leading row. The dynamic force was applied using the Statnamic loading system which produced a lateral force of 3500 kN (787 kips) in about 0.1 seconds. In two cases, dynamic loads were applied following application of 15 static load cycles. In these cases, the dynamic lateral resistance was about the same as the static resistance, likely due to gaps around the pile. In three other cases, the dynamic force was applied prior to the cyclic loading. In these cases, the dynamic resistance was 30 to 60% higher than the static resistance. Simplified analyses suggest that the difference in resistance could be attributed to damping produced by the soil surrounding the piles during the virgin loading.

Jan 1, 2002

By M. Soranzo

This paper presents a restoration operation of the load-bearing capacities of a deep foundation which did not satisfy the original design conditions. The operation was preceded by a series of tests carried out after construction of the pile foundation. In order to verify the efficacy of the method, both load tests on piles before and after intervention and tests on the material used in underpinning the piles were carried out.

Jan 1, 2010

By Roderic A. Ellman

The new Woodrow Wilson Bridge (WWB) will replace the existing bridge over the Potomac River to connect Alexandria, Virginia to Prince Georges County, Maryland. The new WWB will extend approximately 1.1 miles across the river, with a 367-ft long bascule span in the main river channel where the water depth is about 36 ft. The bridge is primarily comprised of fixed spans in relatively shallow water and a bascule span over the navigation channel. The subsurface soil profile was quite variable along the bridge alignment. In Virginia, there was fill over soft Alluvial deposits underlain by dense Terrace deposits, as well as remnant foundations from a former ship yard. At the bascule span, there was up to 50 ft of a soft organic silty clay layer underlain by a deep deposit of stiff Cretaceous clay. Along the Maryland approach, there were Alluvial deposits over dense Terrace deposits over stiff Cretaceous clays and dense Cretaceous sands. The variation in subsurface conditions led to the selection of alternative deep foundations that suited the specific conditions and were based on the design phase testing program, from which ultimate design capacities were determined. During construction, there were instances of unexpected pile performance, notably different than that experienced during the design phase testing, requiring changes to the contract installation criteria and re-design. This paper will present the types of deep foundations used for the project, the performance criteria assumed during the design, the measured performance and difficulties encountered during construction, and the resulting remedial actions, i.e., changes to contract installation criteria and/or re-design due to the unanticipated field conditions.

Jan 1, 2009

By David S. Graham, Paul J. Axtell

Crosshole Sonic Logging (CSL) non-destructive integrity testing identified anomalous readings near the base of a 6.5-foot diameter drilled shaft rock socket. The anomaly was confirmed to be a defect by subsequent coring and core hole camera inspection. A large void and exposed rebar were visually observed in one of the core hole camera inspections. The center of the shaft was then excavated initially with 3-foot diameter tooling and subsequently with 4-foot diameter tooling as part of the remedial actions to address the defect. While excavating with 3-foot diameter tooling, the shaft defect was not encountered. Excavation with 4-foot diameter tooling revealed the defect, a significant void around the majority of the shaft circumference. The void extended radially from the circumference of the 4-foot diameter excavation to beyond the reinforcement cage to the exposed wall of the rock socket around approximately 80 percent of the shaft circumference. CSL results and observations made during remedial shaft investigation and excavation are in good agreement. The shaft defect, located primarily outside of the reinforcement cage, was effectively identified by CSL testing. Although the defect was confirmed by investigative coring, the remedial excavation demonstrates how the investigative coring could have easily missed the defect. This paper shows how CSL results compare to physical observations made during a rare opportunity to characterize the full extent and nature of a drilled shaft defect originally identified as an anomaly by CSL testing. INTRODUCTION The case history presented here pertains to a drilled shaft for a multi-shaft bridge pier in the Midwestern United States. However, the observations presented in this paper are not a result of unique site conditions or the particulars of the project. The lessons learned from this case history are applicable to almost any drilled shaft constructed in the wet. The overall length of the subject shaft is 22 feet including approximately 12 feet of permanently cased, 7-foot diameter shaft extending to bedrock and approximately 10 feet of uncased, 6.5-foot diameter rock socket. The shaft is designed to resist axial and lateral loads and considers the contributions of side and base resistance in the axial design. Six, 2-inch diameter steel Crosshole Sonic Logging (CSL) tubes are include in the shaft. The bedrock at the shaft location includes beds of sandstone, shale, and limestone. The shaft was drilled using conventional drilling equipment and tooling, and water was used as the drilling fluid. Conventional drilled shaft concrete appropriate for underwater tremie-placement was placed via a 10-inch diameter open hopper tremie.

Jan 1, 2019