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By Patrick J. Hannigan, Frank Rausche, Rozbeh B. Moghaddam

Large diameter open-end pipe piles are increasingly used as deep foundations to support heavy onshore and offshore structures. During the driving process, several factors such as subsurface conditions, hammer type, hammer efficiency, pile type, plug conditions, temporarily increased base resistance, and loss of shaft resistance have direct impact on the driveability of large diameter open-end pipe piles. In a uniform subsurface condition, the unit shaft resistance increases with depth. Consequently, more resistance is accumulated as piles penetrate to greater depths which results in higher driving resistance. However, according to the friction fatigue analysis, the greater the number of shearing cycles occurring on a soil segment along the pile shaft, the greater the reduction of its shear resistance. As a consequence, since upper soil layers are subjected to a greater number of blows than those at greater depths, they have a relatively lower resistance compared to what would be calculated with standard geotechnical analysis methods. As a result of this progressive and nonuniform loss of shaft resistance with driving, blowcounts tend to increase at a lower rate than expected from traditional analyses. This paper discusses one of the approaches to the driveability analysis with the geotechnical friction fatigue consideration. It also shows comparisons between predicted driveability obtained from wave equation analysis and field driving records. All analyses were performed for a 2.134 m (7.0 ft) diameter open-end pipe pile installed at a total depth of 192.90 m (554 ft). Two separate static resistance and wave equation analyses were completed for the case study presented in this paper: 1) Friction Fatigue analysis based on the recommendations of Alm and Hamre (2001), subsequently referred to as the FF model, and 2) Standard Driveability analysis based on soil set- up factors, hereafter referred to as the SD model in this paper. Results from analyses included the shaft resistance distributions compared to the result of the signal matching analyses determined from the pile dynamic measurement. Furthermore, predicted blowcounts were compared to observed blowcounts during the pile driving. The comparison analyses indicated a 54.4 percent resistance loss of the Static Resistance during Driving (SRD) due to the geotechnical friction fatigue corresponding to a 46 percent reduction in total resistance. The analyses also showed that average predicted blowcounts using the friction fatigue were 6.4 percent lower than measured blowcounts, whereas, the standard driveability approach showed 42.1 percent higher blowcounts compared to the blowcounts shown in the driving log values.

Jan 1, 2019

By Sanjay Gupta, Sorabh Gupta, Ravi Sundaram, Abraham Varghese

"Geotechnical investigation for the Kochi Metro revealed a critical section of the Viaduct near Ernakulam Junction Railway Station. Four piers, located over a 220 m stretch, were passing through an area with substantial thickness of soft clay. The scope of the geotechnical investigation included two boreholes and a static cone penetration test at each pier location. In the boreholes, field vane shear test was conducted at different depths in addition to the routine SPT. The design of heavily loaded piles in such strata is a challenge due to the liquefaction of the shallow sands and negative skin friction / down-drag in the soft under-consolidated clay. Bored cast-in-situ piles of 1500 mm diameter extending to 50-60 m depth were used to carry 500-600 tonnes load.INTRODUCTIONThe first phase of the rapid transit system at Kochi, Kerala (See Fig. 1) whose elevated route spans from Aluva to Thripunithura covers a total distance of about 25 kilometers. One of the more critical sections of the viaduct exists near the Ernakulam Junction Railway station where the alignment takes a sharp curve to move towards Vyttila, crossing the railway tracks and running partially over the approach of South over-bridge.In this section, four piers located on either side of the railway tracks near the Route Relay Cabin of Ernakulam Junction Railway Station pass through an area with substantial thickness of soft underconsolidated clay.The alignment is geotechincally challenging due to the presence of loose liquefiable sand and soft underconsolidated and sensitive clay.Initial investigations by the owner based on limited boreholes only yielded conservative and inconclusive pile capacities. For a thorough understanding of the soil behaviour, a detailed geotechnical investigation was carried out to assess the engineering behaviour of the soil strata.The scope of the geotechnical investigation included two boreholes and a static cone penetration test at each pier location. In the boreholes, field vane shear tests were conducted at different depths in addition to the routine SPT."

Jan 1, 2015

By Michael Forrest, John Roadifer, Glen Gorski

"The Calaveras Dam Replacement Project (CDRP) requires large disposal sites to store excess excavated materials that could not be utilized for dam construction. Because of access restrictions during design, the disposal site rockfill toe dike area at the edge of the reservoir could not be explored to evaluate soil conditions. As such, the site had to be explored as part of the construction contract. Exploration revealed very soft clay and loose silty sand up to 40 feet thick that would not be able to support the rockfill dike at the toe of a large disposal site fill. Several alternatives were evaluated to stabilize these soils. Based on constructability, cost and risk considerations, cement deep soil mixing (CDSM) was selected as the preferred method of soil stabilization. The challenge was to design and construct the CDSM stabilization to minimize construction delays. A joint effort by the design engineer, construction manager and contractor achieved CDSM stabilization in about three months, from design through completion of construction. A rigorous quality control program included compression testing of both wet grab and cored soil cement samples to demonstrate that specified strength requirements were being achieved.INTRODUCTIONDisposal Site 3 (Figure 1) is one of the primary CDRP disposal sites having a height of 240 feet and a storage capacity of about 2,500,000 cubic yards. An approximately 40-foot-high rockfill dike at the base of the disposal site provides an erosion resistant toe for the disposal site. The rectangular foundation area shown in red was not able to be investigated during design because of access restrictions."

Jan 1, 2015

By Arash Khosravifar, Nason McCullough, Stephen, Milad Souri, Scott Schlechter, E. Dickenson

The results of five centrifuge models were used to evaluate the response of pile-supported wharves subjected to inertial and liquefaction-induced lateral spreading loads. The centrifuge models contained pile groups that were embedded in rockfill dikes over layers of loose to dense sand and were shaken by a series of ground motions. The p-y curves were back-calculated for both dynamic and static loading from centrifuge data and were compared against commonly used API p-y relationships. It was found that a significant reduction in ultimate soil resistance occurred in dynamic p-y curves in partially/fully liquefied soils as compared to static p-y curves. It was also found that incorporating p-multipliers that are proportional to the pore water pressure ratio in granular materials is adequate for estimating pile demands in pseudo static analysis. 1. INTRODUCTION Liquefaction-induced ground deformations can cause severe damage to pile-supported wharves and other waterfront structures. A common approach in analyzing the lateral behavior of piles against seismic loads is using the beam on nonlinear Winkler foundation (BNWF) or p-y spring analysis. One common p-y relationship for sand is the one proposed by the American Petroleum Institute, also known as the API sand model (API 1993). While the API sand model was originally developed for the static loading conditions, it is common to modify the API sand curves for the effects of cyclic loading. However, there is no consensus on how to modify the static p-y curves for the effects of liquefaction and pore water pressure generation in loose granular soils. In previous studies, p-y springs of piles in liquefying soils were back-calculated from case histories, centrifuge model studies (e.g., Wilson et al. 2000; Brandenberg et al. 2005; Abdoun et al. 2003), full-scale tests (e.g., Rollins et al. 2005; Chang and Hutchinson 2013), and numerical analyses (e.g., McGann et al. 2011). In general, these studies found the softening effects of soil liquefaction on p-y curves, as well as a hardening behavior attributed to the dilative response of the liquefied soil around the pile. However, these studies provide varying recommendations on how to modify the static p-y curves to capture this complex behavior. Some design guidelines propose softening the static p-y curves using p-multipliers (e.g., Caltrans 2012). Other studies propose an upward concave shape for p-y curves in liquefied soils (e.g., Franke and Rollins 2013; Chang and Hutchinson 2013).

Jan 1, 2019

By Swaminathan Srinivasan, Aaron J. Muck

"When an opportunity arises to combine state-of-the-art concepts with advanced modeling tools, engineers need to take what they know and apply forward thinking to geotechnical solutions to promote the state-ofpractice. Such an opportunity was seized during the design and construction of the Great American Tower in Cincinnati, Ohio. The forty-one story Great American Tower at Queen City Square – currently the tallest building in Cincinnati – has not only changed the downtown skyline, it is also contributing to the advancement of the state-of-the-art use of auger cast-in-place (ACIP) piles as settlement reducers. Predicted settlements of a traditional mat foundation were excessive, and the costs and construction time associated with traditional ACIP piles extending to bedrock were not preferred. A mat supported on a limited number of ACIP piles, with the piles primarily acting as settlement reducers, was evaluated as the preferred foundation type.Promoting the unique soil-structure interaction of the foundation system with confidence required the use of sophisticated numerical modeling tools. Traditional standard penetration test boring data (SPT) was initially used to develop a numerical analysis of the soil-structure interaction using FLAC 3D software. The model was further modified with cone penetration (CPT) and pressuremeter testing (PMT), along with actual load test results on several ACIP pile elements of varying lengths, but all tipping above bedrock. Through a combined design team effort, and detailed numerical modeling analysis, ACIP piles were recommended for reducing mat foundation settlement. Instrumentation during and post-construction confirmed design assumptions and predictions. Integrating sound geotechnical concepts, and using advanced geotechnical analysis and design methods, traditional mat and ACIP pile foundations were successfully integrated into a unique foundation support system.INTRODUCTIONThe Great American Tower at Queen City Square in Cincinnati, Ohio is located within a region dissected by historical geologic deviances associated with the meander of the Ohio River and glacial progression/recession. Combining a challenging geology, with the development of a high-rise office building afforded the design team an opportunity to combine state-of-the-art soil-structure interaction concepts and method with traditional geotechnical engineering concepts. Such a combination required a variety of field tests, collaboration with the design team and owner, and geotechnical-structural modeling during the design phase. During construction, in addition to materials testing and observation, a variety of instrumentation systems were employed. Together, the data was used to corroborate the design model and make adjustments during construction and further substantiate design assumptions following construction."

Jan 1, 2015

By Frank Rausche, Scott D. Webster, Rozbeh B. Moghaddam

"Pile foundation driveability is a function of several variables such as subsurface characteristics, hammer type, hammer efficiency, pile type, and plugging conditions. One important phenomenon occurring during pile driving, and yet not well documented and published, is the friction fatigue, where a reduction of shaft resistance is observed as the pile is driven to greater embedment. This paper introduces current soil models developed for the assessment of friction fatigue, and further presents a comparison between predicted driveability obtained from Wave Equation Analysis Program (GRLWEAP) and field driving records. From a literature survey, and review of technical articles, a widely-used soil model known as AH-01 has been selected to analyze the friction fatigue concept. Using a WEAP software, two driveability analysis were completed using the standard approach with setup factors, and adapting the AH-01 model into the WEAP input file. Driveability predictions were compared to the driving records corresponding to a 1676-mm x 44- mm open-ended pipe pile with a total and embedment lengths of 180-m and 119-m, respectively. Results from analyses and the comparison presented in this paper provide further information regarding existing methods for the incorporation of the friction fatigue concept to the driveability analyses, and contributes to a better prediction of driveability of open-ended pipe piles. IntroductionDynamic measurements during pile installation provide more dependable information as compared to results obtained from predictive models used for design. Despite uncertainties associated with a specific project site and foundation type, measured data provides a reliable understanding of the soil resistance and its distribution throughout the length of the pile. Back-calculations or back-analyses based on a series of measured data from a pile driving process could help to obtain reliable models to better predict events related to pile installation process in spite of all variability related to fitted models. One of the widely-used analysis regarding pile driving during the design phase is the “driveability analysis” where capacity, blowcounts, maximum stresses in the pile element, and transferred energy from the hammer to the pile element are predicted using mathematical models along with a software. Such analysis requires relevant information regarding soil, pile, and hammer properties combined with a deep understanding of the level of impact each one of these properties could have on the analysis."

Jan 1, 2017

By Thomas W. Scott, Manh N. Tran

Marine environments present a range of challenges for pile construction. This paper contains a discussion on the design and construction of marine piles for a recent Toll Shipping wharf upgrade in Burnie, Tasmania. The project involved several new structures including mooring, berthing and ramp dolphins supported by driven tubular piles with rock sockets, and an onshore mooring dolphin and ramp abutment supported by bored piles. Through the project, a range of construction challenges were experienced, including availability of tubular piles, the different penetration depths of driven piles into rock, the ability to drill out sockets when the piles were raked, the difficulty in verifying the design intent, latent conditions and ship impacts. The paper will present a summary of the different factors that influenced design concepts for the structures involved in the upgrade, and the challenges involved in the design of the structures. Following this, the paper will describe the methodology used to verify the design (including a pullout test), observations made during pile construction and lessons learned on how to limit risk throughout construction.

Nov 1, 2022

By Stefan Schwank, Alexander Blatt, Franz-Werner Gerressen

Diaphragm wall technique is usually used to install diaphragm walls, which are known as underground structural elements commonly used for retention systems and permanent foundation elements as well as deep groundwater barriers, named Cut-Off-Walls (COW). In this exploration project, the diaphragm wall equipment was used in the 2019 summer season to perform the first part of an exploration and bulk sampling program for a potential mine on the Star Kimberlite. Beside the idea of using the diaphragm wall technique as bulk sampling equipment, the sampling program required the adaption of equipment and tools for a depth capability never reached before by a trench cutter in any commercial application worldwide. The paper will explain the development of the sampling program as well as the challenges occurred with the local geology and the specific demands of the exploration and sampling program. It will also provide an overview of the lessons learned during the 2019 season and will give an outlook to the approaches of optimization for the second phase which will be carried out in 2020.

By Wu Jian-tao, LI Guo-wei

"The Cement Mixing Pile (CMP) quality assurance assessment is an important programme in evaluating the efficiency of foundation improvement. Coring is the current specified method of quality assessment in China which has the shortcomings of long cycle, high cost and low efficiency. The field and laboratory test show that the regular cone penetration test can only detect maximum of 4m of effective detection depth in CMP. In contrast, the method of cone penetration test in the reserved hole can detect the quality continuously along the pile at any depth. The tip resistance of reserved hole penetration in the 7th day has good linear relationship with unconfined compressive strength in the 28th day. The slope of linear relationship decreases with the increasing of clay particles content.INTRODUCTIONThe method of Cement Mixing Pile (CMP) is often used to improve soft soil foundation in highway construction, with the major purpose of reducing settlements under embankments (Bruce et al., 2000),which is a form of what is known as the Deep Mixing Method (Bruce et al., 2013). The CMP technology spread quickly in China in the 1980s. CMP quality assurance assessment is an important programme in evaluating the efficiency of foundation improvement. Coring is the current specified method of quality assessment in China (China Academy Of Building Research, 2002). The method of Coring is perceived in some quarters that samples will provide lower strengths given the distress caused to the core during drilling and extraction (Bruce et al., 2002).The cone penetration test CPT can provide continuous measurements of the penetration resistance, sleeve friction at the tip of the probe, which has advantages of simple operation, low cost and high efficiency compared with coring. However, CPT tests have not been established to assess CMP in Sweden because of difficulties in maintaining verticality (Larsson, 2005). In Finland and Norway, however, CPT tests are commonly used (Halkola, 1999). One of the disadvantages of CPT is the tendency of the cone to steer out of the column (Porbaha et al., 2003). Darya Mokrousova (2010) states this tendency to deviate can be overcome by pre-boring and starting the penetration test from the base of the pre-bored hole. Sheng Haiyang (1999) found that probes may be deflected out, sometimes even at small penetration depths, and may not give a complete inspection of the pile. Liu Songyu et al. (2003) suggested that the Standard Penetration Test (SPT) is an effective way to evaluate the strength and quality of stabilized soil-cement columns. In general, Regular CPT can’t test the full length of CMP, and SPT still needed drilling which causes discontinuous detection. From the existing standard of China, core sampling compressive strength test is the main method, evidently, coring displays a longer test cycle, high cost and low efficiency. Therefore, an improvement of CMP quality assessment, by conjuring a fast and reliable detection and evaluation method, is necessary. The aim of this paper is to research the feasibility of using CPT in assessing the quality of CMP and presents an improved CPT method."

Jan 1, 2015

By Craig H. Olson

"A new ship dock at a Philadelphia area refinery will be capable of docking the largest tanker to travel the Delaware River, the Stena V-MAX, which will induce significant lateral loads. The loads at the dock, a system of mooring dolphins and platforms, will be resisted by over 150 pipe piles, including some 20- and 30-in diameter, reinforced, concrete-filled pipe piles and H-piles. Construction included driving the pipe piles to the required ultimate capacity, flushing the pipe pile casing clean of overburden materials, followed by drilling rock sockets into the underlying Wissahickon Formation. The Wissahickon Formation is a complex subsurface that includes variations in depth to bedrock, rock quality, degree of weathering and the presence of very hard quartzite lenses or inclusions. Because of the problematic subsurface, the designers and client requested extensive pile dynamic analysis (PDA) testing by TRC Engineers (TRC).Before beginning, the contractor requested that TRC perform the WEAP (wave equation analysis program) to evaluate the proposed hammer (APE D30-32 open-end diesel) to drive the piles into the proposed bearing strata while maintaining allowable compression stress levels. The WEAP provided a prediction of blow counts and stresses for various ultimate capacities, and showed that for the HP14x89 piles with a required ultimate capacity of 480 kips, a blow count of at least four blows per in at a stroke of 8.0 ft was necessary.New Approachway RampThe PDA testing began at the new dock approachway ramp, parallel to the existing one. The new structure is a 300-ft-long by 21- ft-wide concrete deck supported on seven bents; each has two 24- ft-diameter steel open-ended pipe piles. Every pipe received an HP 14 x 89 x 80-ft pile that was later driven beyond the pipe pile tip to create a composite pile. The pipe piles were later cleaned of overburden materials and finally filled with concrete and rebar. At each bent, a cap was installed on top of each pair of pipe piles, and then a prefabricated concrete deck was added."

Jan 1, 2008

By Reinaldo J. Villa, Joshua C. Adams

The I-395/SR-836/I-95 reconstruction project is an $818-million design-build construction effort that includes construction of viaduct, segmental and signature bridges in Miami leading into Miami Beach in Florida. Based on the load testing performed during the design phase, the design-build team determined that conventional driven pile and drilled shaft foundations were not feasible for support of segmental and signature bridges. Due to the weak limestone formation and successful use of auger cast-in-place (ACIP) piles in the Downtown Miami area on commercial developments, ACIP piles were selected as a foundation system to support bridges. This is the first time in history where the bridges will be supported by ACIP pile foundations in an interstate highway in the State of Florida. The design build-team worked closely with the Florida Department of Transportation to develop requirements for the load test program. The paper will provide an overview of the geotechnical data collected, results of dynamic/bi-directional load testing performed on test piles, data collected, installation of piles, and lessons learned. The load test program included a total of fifteen test piles with dynamic, bi-directional, and lateral load testing on 30 and 36-inch diameter ACIP piles and instrumented with thermal integrity profiling wires.

Sep 8, 2021

By Leonardo Massone

The p-y method is one of the most popular methods in pile design and has been calibrated for various boundary conditions using numerical and experimental studies during recent years. Most studies on reinforced concrete (RC) piles have included the impact of flexural nonlinearity, (e.g. nonlinear moment?curvature relations) but not considered associated pile shear deformations when deriving p-y curves from field data. Common p-y curves may be better applicable for piles with flexure dominated failures (e.g. piles with free- head boundary conditions). For piles with fixed head boundaries (i.e. rotation restrained piles) shear deformations could be of significant influence. To study this problem, a coupled shear flexure interaction model for axial-bending-shear behavior coded in OpenSees is applied to a 0.61 m flagpole and a 0.61m fixed head pile specimen to investigate the possible influence of shear deformations to the overall pile responses. The surrounding soil is represented by p-y curves derived from prior large scale testing on piles with similar boundary conditions. Analysis results show that for flagpole piles, shear forces and shear deformations were insignificant. Considerable contributions of pile shear displacements and forces were observed for the fixed head pile, with shear displacements contributing up to 40% of the total pile displacement. Results suggest that nonlinear shear deformations for reinforced concrete piles should be considered for fixed-head or similar conditions, and that currently used p-y curves may underestimate the actual lateral pile displacement and possibly lead to unsafe design for the particular boundary condition.

Jan 1, 2011

By M. Hesham El Naggar, Tony Sangiuliano, Alper Turan

"Bridge abutments supported on pile foundations are often constructed over weak and compressible soils. The consolidation settlements induced by the embankment loads are known to result in downdrag and lateral forces on the piles supporting the bridge abutments. The performance of a pile group including inclined piles embedded in consolidating soils was investigated numerically considering surcharge loads from approach embankment construction. A two-dimensional numerical model was constructed using commercial finite element software PLAXIS and calibrated against field measurements of the abutment movements observed on Brookdale Avenue Underpass Structure located on the Macdonald-Cartier Freeway in Ontario between Cornwall and the Quebec border. The soft soil model (SSM) was used to simulate the constitutive behavior of the compressible soil deposit. The SSM model parameters were determined based on the laboratory tests. Subsequently, time dependant development of downdrag effects was comparatively evaluated for vertical and inclined single piles as well as a pile group that included both vertical and inclined piles.Results showed that drag loads increased with the consolidation time. However, majority of accumulation of drag loads took place within first 120 days after installation of piles. The results also indicated that the shear forces and bending moments are controlled by the lateral spreading of foundation soil and their accumulation is proportional to consolidation time. The large axial strains caused by large downdrag forces are considered to have yielded the piles and this is a possible reason for unusual abutment movements. The results presented in this study are considered to be of interest to researchers and practitioners.1. IntroductionDeep foundation units are widely used for supporting bridge piers and abutments, where weaker surficial soils preclude shallow foundations. Particularly in Ontario, semi-integral and integral abutment bridges are typically supported on end-bearing steel driven piles. The construction of approach embankments over weaker, compressible soils results in significant vertical and lateral soil movements, which induce additional loads on piles supporting the abutments. In order to minimize such effects, preloading and surcharging are commonly employed approaches to avoid unanticipated settlements prior to the installation of piles. Other alternatives such as aggregate pier supported approach embankment are also being studied as the schedule restrictions imposed by preloading and surcharging becomes cost prohibitive (Turan et al. 2012)."

Jan 1, 2015

By Craig H. Olson

"Anew ship dock at a Philadelphia area refinery will be capable of docking the largest tanker to travel the Delaware River, the Stena V-MAX, which will induce significant lateral loads. The loads at the dock, a system of mooring dolphins and platforms, will be resisted by over 150 pipe piles, including some 20- and 30-in diameter, reinforced, concrete-filled pipe piles and H-piles. Construction included driving the pipe piles to the required ultimate capacity, flushing the pipe pile casing clean of overburden materials, followed by drilling rock sockets into the underlying Wissahickon Formation. The Wissahickon Formation is a complex subsurface that includes variations in depth to bedrock, rock quality, degree of weathering and the presence of very hard quartzite lenses or inclusions. Because of the problematic subsurface, the designers and client requested extensive pile dynamic analysis (PDA) testing by TRC Engineers (TRC).Before beginning, the contractor requested that TRC perform the WEAP (wave equation analysis program) to evaluate the proposed hammer (APE D30-32 open-end diesel) to drive the piles into the proposed bearing strata while maintaining allowable compression stress levels. The WEAP provided a prediction of blow counts and stresses for various ultimate capacities, and showed that for the HP14x89 piles with a required ultimate capacity of 480 kips, a blow count of at least four blows per in at a stroke of 8.0 ft was necessary. New Approachway RampThe PDA testing began at the new dock approach way ramp, parallel to the existing one. The new structure is a 300-ft-long by 21- ft-wide concrete deck supported on seven bents; each has two 24- ft-diameter steel open-ended pipe piles. Every pipe received an HP 14 x 89 x 80-ft pile that was later driven beyond the pipe pile tip to create a composite pile. The pipe piles were later cleaned of overburden materials and finally filled with concrete and rebar. At each bent, a cap was installed on top of each pair of pipe piles, and then a prefabricated concrete deck was added."

Jan 1, 2008

By Chris Harnan, Christophe Justino

The European Federation of Foundation Contractors (EFFC) and the Deep Foundations Institute (DFI) jointly published Edition 1 of the ‘EFFC/DFI Guide to Support Fluids for Deep Foundations’ in April 2019. This Guide was prepared by a Task Group comprising experts on deep foundations from contractors, materials suppliers, consultants and academics. The Guide builds on work carried out by the Tremie Concrete Guide Task Group and presented in Edition 2 of the Tremie Guide. The Paper discusses and describes the content of the Support Fluids Guide which presents the state of the art on support fluid management, as well as the R&D work currently being carried out and funded by EFFC and DFI sponsors through an ongoing Field Research Study (FRS) as well as a review of academic research linked to the EFFC/DFI joint effort aimed at improving knowledge and guidance on support fluids. The FRS and academic research will help to improve the understanding of relevant support fluid properties including stability of excavations, interface layer formation, effect of filter cake and the development of new sampling and testing methodology. The Paper also presents the initial findings from the FRS program as well as a discussion on the challenging aspects of support fluid management with emphasis on design, performance, testing, and the environment.

May 1, 2022

By Alex Ryberg, Matthew L. Becker

Several integrity testing methods exist which may be used to evaluate drilled shafts. Each test method has advantages and limitations. On occasion, the results from different test methods may lead to conflicting conclusions, making it difficult to conclusively know which results more accurately represent the quality and integrity of a drilled shaft. This case study focuses on the integrity testing evaluation for two drilled shafts which were constructed using permanent casings and installed through flowing river water. Integrity testing was performed using Thermal Integrity Profiling (TIP) and Crosshole Sonic Logging (CSL) on each shaft. During testing, the influence of flowing water and soil layering needed consideration in the collected TIP data. Similarly, concrete curing time influenced the CSL test results and required the CSL tests to be performed multiple times with additional wait times following concrete placement. To aid in the shaft integrity evaluations, Low Strain Integrity testing via the Pulse Echo Method (PEM) was performed on several shafts and concrete coring was also performed to help further assess the acceptance or rejection of the questionable shafts. This paper presents an overview of the testing methods that were applied, their basic methodology, as well as potential limitations that should be considered when evaluating their results.

Sep 8, 2021

By N. Schmitz

This paper explains how new digital solutions improve reverse circulation drilling operations. Upgrading field-proven reverse circulation drilling (RCD) rigs with new digital technologies enables semiautomated drilling, with upgrade options for fully automated & remote drilling. Key elements of the improvements are electrically controlled valve systems, process instrumentations, a state of the art machine controller and drilling operation via a touch control panel. Automation of core processes, such as adding drill pipes, reduces set-up times, increases machine uptime for drilling and as a result efficiency. While drilling, sensors provide continuous feedback, which is used to automatically adjust e.g. the weight on bit to the optimum; resulting in an increased rate of penetration and less wear and tear. While in the past hydraulic power packs (HPU) have typically been operated at a constant high-performance level with related high fuel consumption, a new interface between the machine controller and the power unit regulates the HPU performance exactly according to the actual drilling operation needs. This leads to significant fuel consumption reduction. The safety benefits of the digital improvements are the ability to remotely operate the rig in challenging site conditions via a mobile operator panel.

Sep 8, 2021

By Sara Anderson, Rachel Nicholls, Tim Chapman, Janice Windle

"In city center sites around the world, and in particular in London, foundation reuse is becoming increasingly widespread as the ground is filled with detritus from previous developments. This paper sets out a systematic framework to consider the need for and benefits of foundation reuse and key issues to be resolved for foundation reuse to be successfully adopted on redevelopment projects. Once foundation reuse has been identified as a potential foundation solution there are several key stages in the design and construction process where the decision to reuse foundations needs to be assessed. The paper concludes by emphasising the importance of ensuring that the foundations being installed now can more easily be reused in the future.INTRODUCTIONThe concept of re-using foundations is not new, and has been adopted on an isolated project-byproject basis for many years. However, over the past decade, interest in the potential of reusing existing piles and caissons within Europe has increased significantly, with a growing interest in the United States of America and Japan. The need has been driven by necessity: on many urban sites the space available for new foundations diminishes with each new set of piles, and these problems can only grow in the future.Initiatives such as the European Union's RuFUS (Re-use of Foundations for Urban Sites) research project have resulted in identification of the key issues for technical viability and risk that have previously hampered potential foundation reuse projects.There is a need to define a systematic approach to the reuse of foundations so that the risks associated with reuse can be identified, managed and mitigated. This requires improvements in knowledge to provide confidence in the long term behaviour of the foundation support and address the risks involved in reusing existing foundations to overcome perceived obstacles in making foundation reuse a realistic option for many sites."

Jan 1, 2005

By Bernard H. Hertlein

"When the Deep Foundations Institute (DFI) was founded, quality assurance and quality control (QA/QC) of foundation construction was rudimentary. Nondestructive testing (NDT) was a nascent technology, known to very few people, and very limited in its capabilities and applications. In the four decades since the DFI became a reality, NDT researchers and practitioners have taken advantage of technological advances to improve those existing testing and analysis techniques, and to create new ones that have all contributed to the engineering body of knowledge. This has enabled contractors to improve the quality and reliability of their products, and engineers to design more efficient foundations.Through its regular series of seminars, publications and annual meetings, the DFI has been vitally important in educating the deep foundations industry about the capabilities and benefits of NDT methods. In turn, NDT results have helped the industry identify problems in deep foundation construction, determine the causes of those problems, and improve design constructability and construction practices to increase the quality, reliability and efficiency of all types of deep foundations. This presentation reviews the evolution of several important NDT methods, and the contributions that they have made to foundation quality.THE BEGINNINGSThe Deep Foundations Institute (DFI) was incorporated in 1976 in the State of New Jersey as a 501(c)(6) non-profit association. The DFI is a consensus organization of Contractors, Engineers, Owners and Suppliers involved with the design and construction of all types of deep foundations. The purpose of the DFI was and still is to improve the planning, design and construction of deep foundations by educating all those involved, sharing best practices, and promoting the adoption of new technologies that improve quality, productivity or safety.This is well expressed in the current DFI Mission Statement: To bring together multi-disciplined individuals and organizations to find common ground and create a shared vision and a consensus voice for continual advancement in the deep foundations industry.At the time the DFI was born, nondestructive testing for verifying the quality and integrity of deep foundations was in its infancy, its growth constrained by the technology, or lack thereof. Some visionary engineers of the time understood the physics of the potential methods, and therefore the possible capabilities, but were frustrated by the lack of technology to work with. Electronic equipment was mostly analog, and the few digital data acquisition systems that were available had such slow sampling rates that they were incapable of recording rapid event sequences or short duration events such as those used in modern integrity tests. For example, Jean Paquet, a leading research engineer at the French National Construction Institute, (Centre Experimentale de Recherche et d’Etudes du Batiment et des Travaux Publics, or CEBTP) patented the frequency-based analysis procedure for the Transient Dynamic Response (TDR) method, aka Sonic Mobility or Impulse Response, in 1974, but it was not until 1977 that analog data acquisition systems became fast enough to turn his theory into a reality."

Jan 1, 2017

By Inc. Pile Dynamics, Daniel S. Belardo, Marcus Galvan, George Piscsalko

Soil nails are often utilized as a temporary or permanent earth retention technique for slope stabilization and for excavation retention for existing or new structures. Soils nails are generally advantageous as installation is relatively rapid and they can be installed beneath existing structures and where site access for equipment is limited. Due to the typically small cross-section of these elements, the inability to inspect the holes prior to grouting/concreting, and the various installation techniques utilized, quality control for assessing the integrity along the entire length is limited. Currently, quality assurance is conducted by load testing to verify the pull out capacity after installation. The load testing is typically done on a small percentage of the total number of soil nails. This paper will provide the results of a demonstration where the new Non-Destructive Test (NDT) method Thermal Integrity Profiling (TIP) was used to access the integrity of several soil nails along their entire lengths. This TIP method has been successfully used for several years to assess the integrity in drilled shafts and ACIP piles. The TIP method assesses the integrity across the entire cross-section and can identify regions where bulges, necks, and insufficient grout/concrete are present. TIP testing can also help assure that the contractor's installation methods are adequate and consistent for the intended design. For the project presented, instrumented Thermal Wire were affixed to the centered tension bars prior to placement in the excavated shafts. Temperature measurements were recorded from the hydration energy generated after grout/concrete placement, capturing the entire heating cycle. Manufactured defects were installed on the center bar at multiple locations. The results and conclusion will be discussed as well as recommendations for future use.

Jan 1, 2017