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By Shyam Chengalath, Johan Jeansson, Magnus Hörman

Down-The-Hole (DTH) drilling usually uses compressed air to power the hammer. However, there are now DTH hammers on the market which instead of compressed air use high pressure water to power the hammer. There are several benefits with using water DTH compared to air DTH, which are discussed in more detail in this paper. From a physics point of view many of the benefits arise from the fact that water is an incompressible media and air is not. Energy consumption is roughly a quarter compared to air, resulting in lower carbon emission and a lower energy bill. In the case of water DTH the water leaving the drill bit in the hole is at a low velocity and ambient pressure. However, with air DTH the air leaving the drill bit in the hole is at a high velocity and high pressure. This means that the risk of damaging surrounding structures in sensitive areas such as urban environments and dams, is greatly reduced with water DTH. In this paper two cases where water DTH is used in jet-grouting applications are discussed in detail. As these cases show there is a clear improvement in productivity when using water DTH hammers.

Sep 1, 2022

By Lucian L. Bogdan

"SummaryActive loaded strand anchors are often used for slope stabilization, retaining walls or tiedown anchors. Normally, strands are tensioned against the structure and wedges are locked inside the anchorages at a certain lock-off load. During the life of the structure, anchors can receive additional loading during a surcharge, seismic event or other activity on the structure.In order to have a reliable ground anchor system, the strand must not slip through the anchorage wedges during its service life. Strand slippage has been reported during lock-off, when dirty wedge plates and wedges have been used. Low lock-off loads are believed to contribute to strand slippage too. Since the initial lock-off load for a ground anchor is usually lower than the lock-load for an equivalent capacity tendon in other types of post-tensioning construction, there is a concern that strand slippage may occur if the load on the anchor increases above the initial lock-off load.Corrosion protection grout, placed after the anchor is locked off, fills the pocket and surrounds the strand and wedges. Some anchor installers believe that the grout will prevent the anchorage from developing additional capacity if the load increases above the initial lock-off load.The load-carrying capacity of an anchorage depends on several factors. Most important are: initial applied load, anchorage geometry, friction between wedge-anchorage-strand and condition of the contact surfaces.The ADSC Anchored Earth Retention Committee considers that the industry should know how wedges behave once the permanent strand anchors are stressed and grouted inside the transition pipe, between wedges and inside the grout cap."

Jan 1, 2005

By Liiban A. Affi

The most difficult task of designing multilevel tieback walls for deep excavation support is the determination of lateral stresses. These lateral stresses act not only on the shored height, but also on the embedded portion of the soldier pile, all the way down to the pile tip. Examples of lateral stresses include uniform surcharge load (soil spoils or equipment), strip load surcharge from Cooper E80 (train loads), line load surcharge (exterior footing or retaining walls), and point loads (cell tower). In this paper we will discuss the various surcharges, do step by step example calculations and show how to take the total lateral stress output and present the design pressures for direct use by the substructural designer. Included is a case study from a project Anaheim Hills, California, USA.

Jan 1, 2010

By Jeffrey C. Schuh, Logan Bloemer, Daniel P. Dietzler

Over the past 30 years, the authors have encountered numerous projects where recognizing the geology, soil properties and groundwater conditions, and considering alternative construction techniques have promoted efficient and cost-saving construction. The construction documents for these projects, produced by various engineering firms, provided basic information on geotechnical conditions. The authors became involved in each project either because there was a problem during design or construction or, as a contractor, won the project because they saw a value engineering opportunity to take advantage of the geologic setting of the project to design and build alternatives to what the designer depicted. Understanding the geologic setting is critical before planning and designing begins. Being able to work with the geology and the materials on site is preferred before specifying more costly and complex solutions, which often require the importing of materials and adherence to unnecessary and/or inappropriate specifications. Failing to understand the geology or not knowing all the techniques available for construction can lead designers to develop solutions that could be inappropriate. This paper presents several examples of value engineering and project performance enhancements developed through knowledge of basic soil mechanics and implementing innovative solutions. History and Background Most people attend DFI meetings, present their experiences, listen to others, and read articles and papers with the hope they can learn from others. Geotechnical engineers and contractors often interface with others in the execution of projects who have, at best, a rudimentary knowledge of geology and soil mechanics. Of course, there is a need for architects, bankers, and regulators, etc., but they typically do not have much interest in the nuances of geotechnical engineering, which relies on both art and science. Thus, significant time is spent educating counterparts in the need for comprehensive subsurface investigation programs and the intricacies of construction in the “dirt,” as they typically refer to soil and rock.

Jan 1, 2019

By Martin Mcdermott, Kevin Tehansky, Robert Ross, Jeffrey Goodwin

A foundation value engineering redesign is a collaboration between the project owner, original design team, general contractor, foundation contractor and redesign team. Without the acceptance and collaborative effort of all the stakeholders, the redesign process is doomed to failure. For the addition at the Hackensack (New Jersey) University Medical Center (HUMC) we had just such a collaborative effort for the drilled shaft redesign. For a successful redesign effort, the collaboration between the foundation contractor and their redesign team needs to fully exploit the contractor’s specific equipment and experience and convey how to apply this to the project as a whole to ensure everyone is confident that the project design goals are being met. For the HUMC project, applied load testing of the drilled shafts (bi-directional and lateral) were used to provide ultimate geotechnical design values for the redesign effort. By utilizing the contractor’s preferred equipment and the redesign team’s testing and application expertise, the redesign collaboration was able to enhance a good design and make it into a great project.

By David Guy, John Stanbury, Gilbert Tallard

"In 2009, storm surge from Hurricane Sandy inundated the Bay Park Sewage Treatment Plant located at El. +4 to +12 (+1.2 to +3.6 m) in East Rockaway, Long Island, NY. With all systems down, raw sewage water mixed in the floodwaters. A recurrence of such an event being unacceptable, and in view of rising future sea levels, a flood protection project was developed by Nassau County with funding coming in large part from the federally funded Sandy Rescue Fund. Designed by Arcadis/Hazen & Sawyer Engineers J.V., the protection took the form of a perimeter barrier capable of withstanding future storm surge. Due to limitations imposed by property lines and existing facilities, a levee design with three different types of cross section was developed to adapt to each location, adding construction complexity. The Long Island subsurface is characterized by beach sand extending to great depth. The clay required for the core and levee cover therefore had to be brought in from out of state. A thin silty clay layer at El. -23 to -25 (-7.0 to -7.6 m) served as an aquitard. The under-seepage was reduced by a hanging cut-off wall designed as a vibrated beam thin wall and filled with a salt water resistant, low permeability, self-hardening slurry.INTRODUCTIONOn October 29, 2009, Hurricane Sandy hit New York City, with a devastating effect on the region. The low lying Bay Park Sewage Treatment Plant (STP) (Fig. 1) serving Nassau County on Long Island was submerged (Fig. 2). All basements and underground mechanical facilities were flooded (Fig. 3) and millions gallons of effluent were released into the waters of the nearby Hewlett Bay which connects via other small waterways to the Atlantic Ocean."

Jan 1, 2016

By Joseph T. Coe, Alireza Kordjazi, Michael Afanasiev

Cross-hole sonic logging (CSL) is a common quality assurance measure for the evaluation of the structural integrity of drilled shafts. The results of CSL can be supplemented by a set of tomographic images generated by cross-hole tomography (CT). Although the same access tubes, sources and receivers are used in both methods, CT has the advantage of providing a higher quality image of the possible anomalies in drilled shafts. Nevertheless, it has been reported in literature that the CSL and CT miss anomalies with sizes of smaller than 10 percent of the cross sectional area of the drilled shaft. This implies poor resolution despite the high-frequency of the stress waves utilized in these methods. This issue with resolution can be at least partially attributable to the fact that CT relies entirely on the inversion of the first time of arrival and ignores the information embedded in the rest of the recorded traces. This study examines the application of full waveform inversion (FWI) to generate a higher resolution image of the possible defects in drilled shafts from the same data used for cross-hole tomography. FWI is a wave-field method that aims to directly match the recorded traces with traces obtained from a numerical model of the domain. This has the benefit of avoiding the selection of the first time of arrival, along with increasing the resolution of the final image due to extracting more information out of the traces. Through a series of numerical simulations, synthetic traces were generated from a drilled shaft with defects of known mechanical properties, dimensions, and location. These traces were then inverted to evaluate the performance of FWI for structural integrity testing of the drilled shafts. INTRODUCTION The presence of construction defects can compromise the structural integrity of drilled shafts and negatively affect their performance (O’Neil 1991; Sarhan et al. 2002; O’Neil et al. 2003; Poulos 2005). Several non- destructive testing (NDT) methods exist that are currently used for the evaluation of the structural integrity of drilled shafts. Cross-hole sonic logging (CSL), cross-hole sonic tomography (CT), and thermal integrity profiling (TIP) are well-established and documented in the industry and practical manuals (Brown et al. 2010). NDT methods prevent the need for coring and excavation and are relatively fast and cost effective. Successful implementation of these techniques has also been reported in the literature (Branagan et al. 2000; Iskander et al. 2001; Mullin 2010; Johnson 2016).

Jan 1, 2019

By A. Ortigão, M. Felix, E. Falk, T. Koehler

"Ground improvement techniques such as vibro-replacement or deep soil mixing are fairly young products in the Brazilian geotechnical market. Soft soils in this country are deep, very soft, have low sensitivity and are challenging. In general, ground improvement techniques are increasingly selected as more costefficient and flexible solutions on infrastructure projects compared to the conventionall technologies such as piled embankments, wickdrains with surcharge or jet-grouting. The geotechnical challenge expansion project for the Porto Alegre Airport, South Brazil, involved a taxiway area of five ha of 8 to 10 m of soft clay deposit. The deep soil mixing (DSM) technique was selected as a cost-effective solution to reduce settlements. As part of the design, an extensive soil investigation programme includ ing laboratory and field trials was carried out to define the most economical slurry-recipe, DSM installation patterns and quality control specs. This paper gives details of the field and laboratory trials and present results.INTRODUCTIONThe International Airport of Porto Alegre in the state of Rio Grande do Sul in Brazil is located in an area with extensive sediments near to Guaíba Bay. During the different construction phases of the airport over the last decades, the soft clay deposits have been a challenge for the local geotechnical community as well as for the specialized contractors (Schnaid et al, 2001). As part of the most recent expansion scheme, a cargo-terminal with a five ha airplane tarmac area will be constructed."

Jan 1, 2015

By Tara Schenk-McFarland, Mark Bliss

Echo Dam, located near Coalville, Utah, is a facility that provides storage for irrigation and municipal use. Original construction of the dam was completed in 1931. Because of seismic concerns, the spillway crest structure and upper chute section, founded on old landslide and colluvial material, were recently replaced. Prior to replacement of these structures, jet grouting of a block of the loose and potentially liquefiable soils, directly beneath the spillway crest structure was selected as the preferred alternative to address the potential for settlement and cracking of the spillway crest structure. The replacement or alteration of the in-place soil reduces the likelihood of seismic-induced excess pore pressure development and subsequent settlements. Core drilling and sample recovery of the production jet grouted columns was completed to verify compliance with the specifications. It was recognized that due to the larger rock sizes within the deposits that full homogeneity of the jet grouted zone was unlikely to be achievable. However, the purpose of this jet grouted section was to strengthen enough of the soil so that widespread liquefaction does not occur. During the jet grouting production many instances of ground fracturing occurred. Fracturing was evident based on grout/air bubbles exiting the surface near some of the grout holes during jet grouting, air bubbles appearing in the spoil pits, and lifting of the ground surface in the vicinity of the monitor during the jet grouting process while the system was pressurized. In one instance, a section of the upstream spillway slab, which was left in place, was cracked due to pressurized grout escaping beneath the slab. The overall results of the jet grouting were satisfactory despite difficulties encountered. The cause of the fracturing is hypothesized and a recommendation is included to reduce the likelihood of this occurring on future jobs.

Jan 1, 2017

By Piotr Kozlowski, Stanley L. Worst, Matthew J. Niermann

Circular secant pile shafts were installed along the tunnel alignments for both the Ohio Canal Interceptor Tunnel project in Akron, Ohio and the Ohio River Tunnel project in Louisville, Kentucky. The diameters ranged from 34 to 51 feet and the depths ranged from 49 to 107 feet. Verticality and concrete volumes were measured on all piles to verify compliance with the design, which for some shafts consisted of a finite element model with multiple openings using unreinforced concrete secant piles. All secant piles were drilled into rock to seal off the groundwater. This paper will discuss the design, construction and quality control of the secant piles for these projects. INTRODUCTION Many Midwest and Northeast cities have Combined Sewer Overflow (CSO) systems which discharge pollutants into waterways during wet weather events. One way to remedy this issue is to provide a temporary overflow tunnel. A temporary overflow tunnel connects to the combined sewer system and collects the overflow during wet weather events, storing the wastewater until the event has subsided. After the storm event, the stored wastewater can be pumped to the treatment facilities and processed as normal. Project Background – Akron, OH The Ohio Canal Interceptor Tunnel (OCIT) project was performed as a result of the Environmental Protection Agency’s (EPA) Consent Decree with the City of Akron, Ohio. This Consent Decree required modification of the existing Combined Sewer Overflow system. The resulting project consisted of a 27- foot diameter tunnel with multiple points of entry to capture the sewer overflow and prevent it from entering waterways. The tunnel is over 6,000 feet long and is as deep as 150 feet below the ground surface; see Figure 1 below.

Jan 1, 2019

By Venugopal Bonani, Kumaran M., Thomas John

Liquid storage tanks are usually located in nearshore or coastal regions with soil profiles containing thick layers of compressible soils. These storage tanks are usually of large diameter up to 90m and carry high loads, and the tanks are supported by heavy deep foundations such as piles. These structures are subjected to huge lateral loads due to wind and earthquake, and any damage to storage tanks with highly inflammable liquids leads to disastrous condition. So, it is important that the top layer of soil (up to the fixity depth) should be strong enough to provide the required lateral load capacity to the pile. In a project for constructing LNG terminal in Odisha containing 2nos of 89m diameter LNG storage tanks supported with pile foundation located near to coastal region, for improving the lateral capacity of existing soil, the top 3m was replaced with compacted engineered fill (GSB). The site was a filled-up area with dredged soil from seabed, the top 5m-10m were soft to medium stiff clay with SPT N less than 10. The lateral design load on pile was 534kN under free head condition. Actual lateral capacity for the strata was around 200kN under free head condition which was less than required capacity as per structural requirements. Therefore, for improving the lateral capacity of pile the top 3m soil is replaced with well compacted engineered fill (GSB) in layers of 150mm and the capacity is proved by conducting initial and routine lateral load tests. This paper describes the properties of the engineered fill used and how the lateral load capacity of pile was improved to meet the design requirement.

Sep 1, 2022

By Balasubramani M., Ramana P. V., Bairagi K.

This paper is a case study of an earthen Cofferdam, constructed for a deep excavation at Intake location in river Aaundha, Maharashtra, India. A 12 m (39 ft) deep excavation was made to construct the Intake well. The natural soil profile at this location is clay followed by rock. An earthen Cofferdam of maximum height 7 m (23 ft) was made around the periphery of the excavation. Cofferdam embankment and excavation slopes were analyzed using the finite element software PLAXIS-2D. Clayey sand was proposed as filling material during design, but clayey soil was used for the embankment formation during execution. The embankment was built up to 5m height in July 2017 and completely submerged due to monsoon. In February 2018 embankment height raised to 7m (23 ft) by filling the soil over the existing submerged embankment. After a few days of completion of the Cofferdam construction, the inside slope of the embankment had started sliding due to continuous dewatering. The design and execution of deep excavation with earthen Cofferdam for waterfront structures are challenging. The selection of filling material for embankment formation and dewatering techniques plays a vital role in the safety and stability of the embankments. Although all the safety measures were taken during the design, execution challenges are unpredictable.

Nov 1, 2022

By Thai Nguyen Ph. D

Dynamic Load Test (DLT) on driven piles has been performed routinely all over the world. In several recent projects, even 100% testing has become a norm where every single pile is dynamically load tested. In these cases, most piles are of uniform sections, making the field analysis (CASE method) straight forward. The CASE method, which has been used for the last 50 years, however, is only applicable to uniform piles to monitor pile driving stresses as well as pile capacities. Signal matching analysis can handle different configurations. However, the analysis used to require user inputs (i.e., non-automatic). Manual signal matching analysis, which can solve non-uniform solutions, traditionally takes hour(s) to complete for one blow. As such, the real-time pile driving stresses and resistances had traditionally been relying upon the CASE method, using typical range of CASE damping (JC). Until 2021, due to the lack of a rigorous instant signal matching analysis for non-uniform piles, no tool was available to help engineers evaluate non-uniform piles in real-time. An inexperienced field engineer may overlook this shortcoming when evaluating peak driving stresses. Furthermore, ultimate bearing resistances for non-uniform piles may require further evaluation to account for the non-uniformity of piles if relying on the CASE method. This paper highlights recent advances in instant Signal Matching Analysis on non-uniform piles, allowing field engineers to monitor stresses and resistances of non-uniform piles during driving.

Oct 1, 2022

By Kalyani Devabhaktuni, Mike Minton, Mark T. Howe, Yan Zhang

During the procurement phase of a Design-Build (DB) project, design-build contractors must often commit to a fixed price based on limited or incomplete geotechnical information. This lack of information can result in an inaccurate assessment and allocation of project risk to either the contracting authority or the DB contractor. This paper presents a case study of an elevated water tank supported by mixed ground improvement techniques, including Vibro-Compaction (VC), Aggregate Piers (AP) and Compaction Grouting (CG) in East St. Louis, Illinois. An adaptive design and contracting approach provided the best value solution for a complicated set of geotechnical problems, including static bearing capacity and settlement concerns as well as liquefaction induced settlement. Close cooperation between the owner, the tank contractor, the geotechnical engineer and the ground improvement contractor was essential to produce an effective solution. Ground Improvement techniques resolved the geotechnical challenges at the site through adaptive design methods, utilizing progressive rounds of verification and real time data acquisition to achieve performance objectives. This paper details the evaluation of geotechnical criteria, the selection of ground improvement techniques, the adaptive design and implementation of ground improvements, as well as contracting methodologies used to ensure that the best value was provided. PROJECT INFORMATION In November, 2016, CB&I Storage Tank Solutions (McDermott) submitted a design/build proposal for an elevated water tank for Illinois American Water Company (IAW) in East St. Louis, Illinois. The purpose of this tank was to have backup water capacity for power generation. In the RFP, IAW requested two alternate styles of tank: Option 1, a 1250 Million Gallon (MG) Composite Elevated Tank or Option 2, a 1250 MG Waterspheroid tank. Option 1 consisted of a steel tank supported on a concrete tower. Option 2 consisted of a steel tank supported on a steel shaft. The height (determined by IAW) was 140 feet to the top capacity line measured from top of floor slab.

Jan 1, 2019

By Peter Middendorp, Gerald E. H. Verbeek

"This paper will describe a brief history of the method of characteristics as an accurate solution of the wave equation, and the author's experiences with the method of characteristics over a period of 30 years.As a result of the offshore pile driving activities associated with the development of the North Sea oil fields in the 1970's, two Dutch companies initiated extensive research efforts. Heerema started to research the dynamic behavior of soil during driving and HBG (Hollandsche Seton Groep) extended the method of characteristics with a straightforward theoretical solution for the shaft friction along a pile.The research institute TNO started the development of the wave equation program TNOWAVE in the late 1970's based on HBG's friction model extension for the method of characteristics. Today the program has a worldwide application in the field of pile testing. This paper will describe its development and application over time and its relation to today's applications for driveability studies for impact hammers (PDPWAVE) and vibratory hammers (VDPWAVE), signal matching for Dynamic Load Testing (DL TWAVE), Pile Integrity Testing signal matching (SITWAVE), and Statnamic simulation (STNWAVE).The paper will highlight that these developments have been the result of multi-disciplinary and multi-national efforts and encourage geotechnical engineers to seek further developments of the wave equation program in a similar manner. Finally, the paper will indicate some areas where such further developments are required."

Jan 1, 2005

By Filippo Maria Leoni, Alessandro Bertero, Gianluca Pianezze

"As part of the Southeast Louisiana (SELA) drainage program, designed by the U.S. Army Corps of Engineers (USACE) to reduce flood damages in the City of New Orleans and surrounding parishes through the construction of new pumping stations and better drainage canals, the SELA-22 project entailed the installation of a concrete covered canal along Jefferson Ave. and Prytania Street, in a highly urbanized portion of Uptown New Orleans, LA. The scope of the required soil improvement was to replace the soil between two parallel lines of sheet piles with a soil-cement mass to eliminate underseepage and provide structural support for the concrete culvert. The USACE selected the jet grouting (Jet Grout) technology for the construction of the bottom plug. The bottom plug is between 18 and 21.5 ft thick with a maximum depth of approximately 40 ft, for a total length of approximately one mile. The treated soil comprised soft clays and silts with occasional presence of sands. Project specifications required 100% area coverage, a 28-days unconfined compressive strength of 100 psi and hydraulic conductivity of 1x10-6 cm/s, to be verified by testing specimens from cored samples. The specialty geotechnical contractor proposed to accomplish the task utilizing their proprietary and innovative elliptical bi-fluid Jet Grout technology, and elected to perform a pre-construction bench scale laboratory mixing program to determine the most suitable grout mix features (i.e. binder type and proportions, binder content, etc.) to be applied in the subsequent field test and production stages. This paper will summarize and compare the results obtained from the different pre-construction and construction stages; interpretations of the data will be provided, along with general considerations regarding the effectiveness and significance of bench scale testing for jet grouting applications.INTRODUCTIONIn general, the effectiveness of the construction parameters in any ground improvement work depends largely on the physical and mechanical properties of the soil to be treated. Therefore, well designed laboratory and field test programs, aimed to disclose the interaction between the site-specific soils and the mixing parameters, are essential to achieve the desired end product."

Jan 1, 2016

By Scott A. Walker, Gabriel J. Alcantar, Brian Zuckerman, Ramin Golesorkhi

"The stadium development consists of construction of a 68,500-seat, open-air NFL football stadium for the San Francisco 49ers. The main structure will consist of a 7-story above grade steel structure supported by over 3,000 piles. Berkel and Company Contractors, Inc. (Berkel) was selected as the design-build pile contractor who used their auger pressure grouted displacement (APGD) piles for this project. During an indicator pile installation and pile load test program, fifteen piles were tested to develop installation criteria to support demands of 150kips tension and 180 kips compression. Following the indicator pile program Berkel installed 3088 piles in 30 working days. Throughout pile installation data were collected with an automated data acquisition system (DAS). During pile installation field engineers from Treadwell & Rollo observed the pile installation as well as the real-time data from the DAS. Strategic staging and pre-production planning by Berkel along with consistent collaboration with the design team created an atmosphere for a successful and on schedule project completion.IntroductionThe new San Francisco 49ers Stadium in Santa Clara, California will be a 68,500-seat facility, a rendering of which is shown in Figure 1. The main structure will consist of a 7-story above grade steel structure supported by more than 3,000 piles. The north, east and south portions of the stadium are designed as an open seating bowl, while the western portion includes open seating at the lower levels and seven-story tower which houses over 150 suites.The stadium project includes the stadium structure, as well as elevated open pedestrian walkways, commercial community space, and three new pedestrian bridges spanning a nearby by creek. Sustainable designs and innovations such as a green roof, photovoltaic panels, a ground source geothermal system, stadium-wide Wi-Fi capability, and access to public transit are provided throughout the project. The stadium is designed as an open, light, and airy structure and is surrounded by an existing amusement park, office buildings, the Santa Clara Convention Center, and the training facility of the 49ers."

Jan 1, 2015

By Dan Brown

Deep foundation contracting for transportation projects in the United States has typically followed the design-bid-build model in which contractors bid on a specific work product according to relatively inflexible prescriptive specifications. With continuous flight auger piling and the many types of proprietary drilled displacement auger piling, there appear to be advantages to contracting this work according to a different model. This paper provides a discussion of the use of a performance specification for this work in which the contractor has greater freedom to choose the most appropriate foundation system and also greater responsibility for the performance of the completed foundation. With public agencies subject to open bidding, this type of contractual arrangement presents opportunities to encourage innovation. There are also challenges for implementation in public works projects, notably the selection of qualified contractors and the verification of performance requirements on production foundations.

Jan 1, 2006

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 T. Wulleman, M. Ansriou

Integrity testing is a primary quality control check on a product that is for the most part not accessible to visual examination. Their cost can be expensive when using direct methods of inspection (like coring a pile) or more economical when using indirect methods (e.g. acoustic testing). All indirect methods operate by “inference” which means that they do not directly measure the defect of integrity. Indirect methods measure the variation of physical values (temperature, impedance, speed, ect.) correlated to the integrity of the pile allowing the detection of integrity defects, although these methods do not allow for the characterization of the defect. 1. INTRODUCTION Cast-in-place piles are particularly prone to integrity defects. The reasons for this are multiple, including lack of high quality of contractor workmanship, experience and supervision necessary in construction, variable soil and groundwater conditions on site, etc. Furthermore, visual inspection of the finalized pile is usually impossible. Therefore, special care has to be taken both during the execution process and during the subsequent quality control campaign to detect any defects of executed piles. Today, a lot of methods do exist to assess pile integrity. It is thus essential to understand the mechanism governing those devices to both make an engineering choice of the pile integrity testing method and to interpret correctly the provided results. 2. QUALITY IN PILE FOUNDATIONS 2.1 Pile anomalies A pile having an anomaly is a pile which has a different behavior from what is normally expected. The presence of a pile anomaly does not necessarily imply that a pile cannot be used for its intended purpose (Gordon & Chapman 2004). An anomaly can be considered as a defect, or a “performance” depending on the ability of the pile to fulfil the following three criteria (3C): C1 - Meet the Service Limit State (SLS) requirement and support the proposed working load without settling more than admissible by the superstructure ; C2 - Meet the Ultimate Limit State (ULS) requirement and carry a specified load with an adequate factor of safety against failure ; C3 - Remain durable throughout the design life of the structure such that the pile is not affected by time dependent activities (chemical attack, corrosion of steel reinforcement, ect.), which would jeopardize its ability to maintain its compliance with the first two criteria.

Jan 1, 2019