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By Shahid Islam, Lucian Bogdan

"The maintenance of infrastructures has been of particular concern to the engineering community. As the world’s infrastructure expands and existing infrastructure ages, monitoring and evaluation of the structures have become more critical than ever. A large number of retaining walls, tie backs, slope stabilizations and piles are designed using pre-stressing steel. Many piles and drilled shafts are designed using reinforcing steel. There are few testing methods available to assess these tension and compressive forces. High cost, complicated equipment and limitation of space often prevent these methods from being implemented. DYWIDAG-Systems International (DSI) has been involved in the development, testing and utilization of DYNA Force® sensors to measure the force in the anchors during construction and at any time during the lifetime of the structure. They can be used for bare, epoxy-coated, galvanized and greased-sheathed steel in the bonded, un-bonded, grouted or un-grouted length of the anchor. The sensor is robust and requires no maintenance. Sensors have received attention in terms of accuracy, performance, ease in installation, durability, and cost effectiveness. This paper describes its application in tie-back and anchor force monitoring of retaining walls and bridge abutment and compression forces in drilled shaft reinforcing steel where the data were collected manually, automated and remotely.INTRODUCTIONOur infrastructure is expanding and the existing infrastructure is aging. Some structures are expensive to maintain and some occasionally fail. There is a large demand for implementing health monitoring of structures. Many tie-backs, retaining walls, dams and other geotechnical structures are post-tensioned and many of them need repair using a post-tensioned system. On many occasions during construction and service life of the structure, it is useful to know the force in the post-tensioning and anchor system. Many piles and drilled shafts are designed using reinforcing steel and the compressive forces in reinforcement are unknown. Although there are many methods to measure the tendon force, most of them are cumbersome, expensive, and the accuracy varies depending on the method used.The elasto-magnetic (EM) technology is a novel approach to monitor forces in steel elements. The DYNA Force sensor is built based on EM technology (See Fig. 1). It is composed of a primary coil and a secondary coil (sensing coil). By passing current through the primary coil, ferromagnetic material is magnetized. The sensing coil picks up induced electromotive force that is proportional to change rate of applied magnetic flux (Faraday's law) and relative permeability. As permeability of core changes, output voltage changes. The output voltage is calibrated to measure the force. A readout unit is designed to magnetically energize the steel through the sensor and measure the response of the steel to the process. The readout unit then converts the response into a direct force reading. The sensor has an embedded thermistor which allows for temperature compensation. Due to the diversity of the magnetic property of steel, calibration is done for each type of steel allowing the sensors to perform at their highest accuracy."

Jan 1, 2017

By Sandeep Pattnaik

Spring stiffness of soil and rock at different depth is often required for a pile structural model. If the pile is rested in multiple layers of soil, then it is rather more complex to simulate the soil in a structural model. The spring stiffness will vary based on density of soil strata over the depth. When a pile is socketed in weathered rock followed by a soil layer, a sudden change in subgrade modulus can influence the pile deflection drastically. Determination of soil spring and simulation of the pile in this condition required correct interpretation of subgrade modulus. The conventional approach of pile spring calculation underestimates the spring stiffness by ignoring underlaying stiffer layers. A finite difference method (FDM) of analysis can reasonably estimate the p-y of soil / rock based on subgrade modulus of each layer. However, the transition between the layers can be better simulated as per the deflection pattern of the pile. The lateral deflection of the pile is mainly dependent on the stiffness of soil layer surrounded by the pile. Generally, the lateral influence of a pile varies from 4D to 6D depending on the soil type. Therefore, soil spring stiffness around the pile would require special attention of a Geotechnical engineer to avoid uncertainty in the prediction of pile behaviour. In this paper, emphasis has been given to develop an approach for pile spring stiffness design. A standard software program LPile has been used to develop p-y curves of soil and rock layers at different depths and then converted to soil/ rock springs over the depth. Modulus of Subgrade Reaction as given in IS 2911 (Part2) was also used to correlate the spring value for different type of soil. Obtained analytical results were compared with full scale field trial for lateral deflection of pile. A good agreement between these two approaches has been established. The effect of soil structure interaction in the structural model shall be simulated by assigning an equivalent vertical and horizontal soil spring, which is developed by Winkler’s soil spring approach. A simplified design principle for calculating the pile spring is discussed in this paper. This approach has been extensively used in Mumbai metro elevated line pile design.

Nov 1, 2022

By Achyut Kumar Allady, Praveen Arumughan

NCHRP Synthesis 418 (2011) entitled, “Developing Production Pile Driving Criteria from Test Pile Data” details the occurrence of dichotomy between pile Skin resistance and pile Tip resistance mobilizations at different times for different hammer blows during pile driving operations. With increasing usage of High Strain Dynamic Testing (HSDT) the engineering community started paying more attention to this occurrence of dichotomy resulting in overdriving, pile damage, increased claims, and loss of time. To overcome the dichotomy limitations of HSDT, NCHRP recommends, “the use of superposition to combine the back-calculated tip resistance from a blow on initial drive or from redrive with the back-calculated skin resistance from the early blows at the beginning of restrike”. However, the current practice of external mounted gauges and signal matching for a single blow are unable to evaluate independently the Skin resistance and Tip resistance to achieve the goal of determining the optimum Total Pile Capacity using the superposition. This paper discusses advancements of science and technology with sensors embedded at the pile top and pile tip, the data collected is analyzed by the state-of-the-art FDOT Method to determine Skin and Tip resistances independently for every blow. Independent Tip and Skin resistances each with a Resistance Factor can be summed up to obtain optimum Total Pile Capacity. Additional benefits of determining independent Skin and Tip resistances include obtaining lost skin capacity due to scour, due to pre-drilling/preforming and uplift tension capacity. Furthermore, the benefits of embedded sensors include increased quality control/quality assurance through 100% testing, accelerated construction, life cycle monitoring and asset management.

May 1, 2022

By Thomas J. Kennedy, Michael D. Bennett

The study of geotechnical history is well-established. Most geotechnical practitioners, teachers, and graduate students have some grasp of the origins of the field. However, this understanding often consists of a jumble of names and anecdotes. This paper discusses how a deeper comprehension of geotechnical history can benefit academia and practice alike and describes how the authors have begun a wide-ranging study of the subject. The paper reviews the dual-track methodology the authors have generated for the study, which consists of written articles about different works in geotechnical history and a database tracking how often pieces have been cited in geotechnical literature. The first technique has shed light on aspects of geotechnical history such as the connection of the Darwin family to the origins of geotechnical engineering, the St. Francis Dam failure of 1928, and the rivalry between theoreticians and practitioners in the early days of the field. The second has helped quantify subjects such as the outstanding contributions of Karl Terzaghi, the disagreements between Terzaghi and Donald Taylor, and the specialization of the field over time. The paper concludes by discussing the authors’ planned future work on geotechnical history.

Oct 1, 2022

By Gustav Jahner, Michael Baltrusch, Norbert Hoffmann

Near the port city of Whitby in the north-east of England, Anglo American (AA) is setting up the deepest mine in the UK, which will have a depth of 1,500m. The purpose of the project is to extract and transport polyhalite, both underground, and to market it globally. As part of the construction works, BAUER Technologies Ltd, the UK subsidiary of BAUER Spezialtiefbau GmbH, constructed three different shafts using the diaphragm wall technique, with depths of up to 120m. In order to ensure the specified vertical tolerance of maximum 200mm, several measurement methods were applied, and the results were documented in a 3D model. Complex de-sanding plant technology and specially developed polymer products were adopted to regenerate the trench supporting bentonite-slurry.

Sep 1, 2022

By Robert C. Simpson, Ghada S. Ellithy

"There are several methods for estimating the axial capacity of drilled shafts installed in coarse-grained soils. Most methods estimate the ultimate capacity for side friction and tip resistance. Design capacity is then calculated by applying a resistance factor to the ultimate capacity. In reality, however, ultimate resistance may not be mobilized except after a significant displacement that is not structurally tolerated in either compression or tension modes.A full- scale load test is the best way to obtain the load settlement curve for a drilled shaft, especially in soil formations where accurate estimation of soil frictional properties from a field investigation may be difficult. This paper presents the results of a static, axial, compressive bi-directional load test, using the Osterberg method (O-cell test). The test was designed so that the shaft above the O-cell would move up and the shaft below it would move down when loaded. At the start of the test the concrete around the O-cell is fractured generally on a plane near the bottom of the cell.The test was designed to validate the design capacity of drilled shafts embedded into the Vashon recessional outwash (Qvro), which is a glacially derived sediment consisting of thick deposits of cobbly sand and gravel relatively free of silt and clay found in the Seattle, WA area. The test shaft consisted of a 2.5- feet (0.75 m) diameter drilled shaft. The test shaft was installed to a depth of about 47 feet (14.3 m) into this formation. A maximum load of 437 kips (1.95 MN) was applied during the test, in each direction. The maximum load was attained at upward and downward displacements of less than 0.1 inch (2.5 mm), respectively.Although the load test did not yield ultimate values, the results are compared to the design assumptions using methods adopted in the FHWA and AASHTO guidelines, which verified the adequacy of the design assumptions. We conclude that more emphasis is needed in the prediction of the service loads and corresponding mobilized displacement that may lead to a more cost effective design. It is also clear that more testing to higher loads could lead to more efficient designs on specific projects and generally as data is added to the local knowledge base."

Jan 1, 2015

By Jeremiah M. Jezerski, Russell H. Lutch

The Mount Olivet Road Drop Shaft (MOR-DS) support of excavation (SOE) is a circular unreinforced concrete shaft with an inside diameter of a 30.5 ft (9.3 m) and depth of 120.5 ft (36.7 m), constructed using slurry wall methods. The SOE for the adjacent Mount Olivet Road Approach Channel (MOR-AC) and Mount Olivet Road Ventilation Vault (MOR-VV) near surface structures (NSS) consists of lean mix concrete walls and cement-bentonite walls, respectively, both constructed using slurry wall techniques and reinforced with embedded soldier piles. NSS SOE required multiple levels of preloaded internal bracing, with excavation depths of up to 75 ft (22.9 m). The original design construction sequence for the shaft and NSS SOE required that the MOR-DS be constructed in its entirety and backfilled to ground surface prior to excavation of the adjacent NSS SOE. After installation of the drop shaft and NSS SOE an accelerated construction sequence was implemented requiring the analysis of the excavation support systems to determine if the excavations could be open concurrently without adversely impacting the partially constructed permanent MOR-DS structure. The MOR-DS was analyzed using the finite element analysis (FEA) software, MIDAS GTS, to demonstrate that the unbalanced loads applied to the MOR-DS composite structure due to the revised sequence would not exceed the strength and serviceability requirements per ACI-350 or superseded by the more stringent project requirements. The results of the FEA were used to set limits for geotechnical instrumentation consisting of strain gauges located on the brace levels of the NSS SOE. A comparison of the SOE design hand calculations, FEA model results and instrumentation data is presented.

Oct 1, 2022

By Jamey Rosen, Georgette Hlepas

Verticality data collected from panel and pile elements of seepage barrier walls describe the shape and position of those elements in three dimensions. These data are used to determine if a barrier wall is constructed as designed and if it meets the owner specifications with respect to tolerance (i.e., if each element is sufficiently close to vertical) and overlap (i.e., do adjacent elements overlap sufficiently to prevent leakage). Contractors use verticality data to confirm that their work matches the design, and owners use verticality data to verify the contractor’s work and confirm that specified criteria were met. Project Information Management Systems (PIMS) technology has been applied to the management, visualization, and analysis of verticality data. This paper will provide examples of how contractors and owners have used a PIMS to compile and synthesize data collected during excavations (e.g., from Cutter Soil Mixer and Hydromill drill rig telemetry), and from measurements of completed excavations (e.g., using the Koden ultrasonic tool), and used those data to model excavation geometry. We will present case studies of using these models to estimate backfill placement volumes, and to evaluate the verticality tolerance and overlap between elements.

Sep 8, 2021

This Section describes four alternative methods for load testing of drilled shafts: high strain dynamic test (HSDT), rapid load test, static load test, and bottom load test. Until recently, static load tests were the only method available for verifying the capacity of a drilled shaft. However, because many drilled shafts carry very high design loads, the static load test was prohibitively expensive. The alternative methods, HSDT, rapid load testing, and bottom load testing are gaining acceptance because of their lower cost and faster implementation. However, these different methods do not necessarily yield the same results. This section describes the load testing methods and the differences that may occur when interpreting the test results.

Jan 1, 2004

By Venkatesh S. V J, Shubha M, Srilakshmi G

Choosing for the best option of pile foundations to overcome large lateral and uplift loads for the foundations in transmission line towers/offshore environment is still being a concern to achieve the required capacities but also by considering the suitability aspect in the environment. The objective of this paper is to review the methods that have been done for knowing the uplift resistance and lateral resistance of pedestal piles. Investigations by different methods such as experimental studies, numerical and analytical studies have been done by various researchers in order to evaluate the response of a belled pile. These methods are discussed in this paper and the comparison with straight shaft pile based upon the test and analysis. The results indicated that the uplift resistance and lateral resistance were significantly increased with the adoption of belled piles than straight shaft piles.

Sep 1, 2022

By Konstantin G. Ashkinadze

The paper considers performance of piles supporting transient pipe anchors in heavy industrial pipelines. Events such as pump trips or opening and closing of large valves produce short-term dynamic pulses in the pipeline with variable spectral characteristics. Their magnitude is large enough to cause major damage to the pipeline and its anchors, which face horizontal impact loads amounting to hundreds of kN. Design of pile foundations supporting these anchors is often governed by limitation of deflection of the support to prevent overstressing pipeline connections and equipment nozzles. The maximum deflection does not always correspond to the largest load because the stiffness of the soil surrounding the piles heavily depends on the rate of loading. Faster actions encounter stiffer soil response while loads of smaller magnitude applied slowly may be more critical for the deflection time history of the anchor. A typical transient action has both high- and low-frequency harmonics, which makes the response complex. Using load rate-dependent p-y curves published in literature, the paper develops methods of analysis of pile foundations for transient anchors. Pile displacement amplitude – input frequency – natural frequency correlations and time histories of pile response are constructed for typical profiles of transient actions, considering nonlinear soil response to large horizontal loads.

Jan 1, 2016

By Gerald Verbeek, Erick Baziw

"Downhole Seismic Testing (DST) is an important geotechnical testing technique for site characterization as it provides low strain (<10-5) in-situ interval compression (Vp) and shear (Vs) wave velocity estimates. These velocities are determined by obtaining relative arrival times of source waves as they travel through the stratigraphy and are recorded by one or more vertically offset seismic sensors. A challenging aspect of this process is to characterize the seismic data sets to determine the analysis method that will result in the most accurate interval velocity values. This paper introduces an assessment technique which utilizes linearity estimates (i.e., hodograms fitting straight lines) from the polarization analysis in conjunction with crosscorrelation coefficient calculations of the full waveforms as well as the deviation of the source wave frequency spectrum from a desirable bell-shaped curve. The paper will provide an overview of the technique and include some examples of actual data sets where the technique was applied to analyze those data sets.1. INTRODUCTIONIn general terms, Downhole Seismic Testing (DST) such as Seismic Cone Penetration Testing (SCPT) is a geotechnical technique for measuring in-situ shear and compression wave velocities (VS and VP respectively). The main goal in DST is to obtain arrival times as the source wave travels through the soil profile of interest, and from these arrival times the velocities are then calculated. Figure 1 shows a schematic of the typical DST configuration: a seismic source is used to generate a seismic wave train at the ground surface. One or more downhole seismic receivers are used to record the seismic wave train at predefined depth increments. The downhole receiver(s) may be positioned at selected test depths in a borehole or advanced as part of an instrumentation package as in the case of SCPT. When triggered by the seismic source a data recording system records the response of the downhole receiver(s)."

Jan 1, 2017

By Takeshi Maki, Kh. Adeel Tariq

"The lateral resistance of the structure plays an important role during seismic event and it can be increased by using ground improvement. In this study an attempt has been made to investigate the effect of cement-treated sand on the lateral capacity of the pile. The behavior of piles surrounded by sand only and cement-treated sand confined in a steel box (30 x 30 x 50 cm) which is subjected to lateral cyclic load has been investigated. Piles having a diameter of 2.5 cm and embedded to a depth of 45 cm were used. Steel and aluminum piles were used to investigate the effect of flexural stiffness on the lateral capacity of the pile. Bottom supports of piles were also changed from pinned to fix. Well graded sand compacted to 70% of relative density (RD) was used. Cement-treated sand having a compressive strength of 3.7 MPa was used. Displacement controled lateral load tests were performed and cyclic loads were applied until pile displacement was 4%, 10%, 20%, 35%, 50%, 75% and 100% of pile diameter. Results evaluated are compared with common method of analysis like Brinch hansen (1961), Brom (1964), Poluos (1980) etc. Results have indicated that the stiffness of a pile affects its lateral capacity. The introduction of central cement-treated sand part increased 5 times the lateral capacity of piles as compared with a sand only condition.IntroductionPiles are used extensively around the world to support loads of structures. Piles are commonly used to carry axial load, but in some structures, the lateral capacity of the pile is more important than the axial capacity: for example piles supporting earth retaining structures, electric tower foundation, etc. Structures can be subjected to both axial and lateral forces, like structures constructed at harbor that are subjected to lateral force due to waves action; and structures built in earthquake prone areas like Japan."

Jan 1, 2017

By Shawna Munn, Nadir Ansari, Allison Bennett

"This paper outlines how specification driven design has made Toronto Area transit infrastructure projects more expensive than similar private projects, and provides a case study of the results of an excavation at Launch Shaft 1 (LS1) for the Eglinton Crosstown Light Rail Transit project in Toronto, Ontario. The paper will describe the impact specification driven design parameters can have on design economy, constructability, and schedule and will suggest an alternative approach utilizing the Observational Method. As a result of the initial specification based design, Isherwood was retained by both the General Contractor and the Specialty Excavation Shoring Contractor to provide value engineering leveraging the Observational Method to improve constructability and construction schedule. By using well known, accepted design methods coupled with local experience in lieu of the specified design pressures and parameters, the redesigned bracing scheme reduced construction cost and schedule. This excavation case history can be a lesson learned for future transit projects.The City of Toronto has been developing its transportation network since the mid 1800’s. “Canada’s First Subway” along Yonge Street opened in March 1954 (TTC 1954), with a few additions to the subway network through to the 1980’s. The following two decades marked a long period of slow development due to recessions, budget cuts, and politics along with several cancelled projects. To fill the gap left by years of underfunding, several new transit projects are now under construction in the city as a part of Metrolinx’s $50B, 25 year, “The Big Move” initiative (Metrolinx 2013). The work on these types of infrastructure projects is highlighting a different and developing challenge within the tendering and design specification structure we will call Prescriptive Specification Design (PSD).PSD is a method used within contract specifications to control design risk on a project by applying conservative design methods, factors of safety, or other parameters to make a “fool proof” design. It is akin to requesting a colouring by numbers approach from a painter. There are inherent risks of using this method of tendering a project including increased project costs, longer construction schedules, and decrease of overall project economy. In PSD, the Owner “owns” all of the design risk on a project, including any additional costs due to changed site conditions. However, the Contractor commonly “owns” the risk of any deviations from the design specification they pursue, therefore making any improvements to the design, cost, or schedule less desirable from the Contractor’s point of view. The impact of this type of strict specified approach to design has been seen in transit infrastructure projects in the Toronto area. Figure 1 outlines the range of specified AEPD design pressures as a function of excavation height (H) specified for use in Toronto underground transit projects since the 1970’s to present day. A clear trend can be seen with respect to increased design pressures specified. The ranges shown for each project are intended to account for the potential differences in soil conditions for the highly overconsolidated glaciated soils in the Toronto area. The graph also highlights the typical range, in blue, for the industry practice in Toronto for comparison."

Jan 1, 2017

By Remco Offenberg, Marcel Bielefeld, Martijn van Delft

The question of the continued suitability of existing foundations arises when the function of the superstructure changes. This can occur when the superstructure is replaced or when the existing structure is expanded, leading to higher loads on the existing foundation. Quite often it is a challenge to define the suitability (with respect to integrity, bearing capacity or both). The lack of information on the existing foundation (such as pile dimensions, installation records, original soil investigation, design calculations, etc.) makes it frequently seemingly impossible to assess whether the foundation or foundation elements can be re-used. The paper outlines the tools available to an engineer to evaluate existing foundation piles for potential re-use. The paper illustrates the application of these tools through a few case studies from The Netherlands, including the evaluation of a 400 years old bridge foundation to address increasing traffic loads.

May 1, 2022

By Zaw Zaw Aye, Sereyroath Chea, Nutthapon Thasnanipan, Thayanan Boonyarak

"As there are only limited numbers of bored pile constructed in sandstone and siltstone in Thailand, load transfer and settlement behavior of a pile in these rocks are still not fully understood. Major factors which influence the performance of the pile in the sedimentary rock should be systematically investigated. The objective of this paper is to analyze load distribution and load-settlement behavior of bored pile in sedimentary rock. Interpreted data was obtained from instrumented load testing results of large-diameter bored piles. These piles were drilled in aeolian soil and socketed in sandstone or siltstone, having socketed length varying from 1 to 3 times the pile diameter. Factors that influenced pile settlement behavior, consisting of rock type at the pile base, socket length, at-rest earth pressure and rock conditions, were analyzed. For interpretation of results, analytical solutions were used to estimate load bearing capacity and calculate settlement of each pile. According to test results of mobilized unit skin friction in siltstone, relationship of 0.1 – 0.3 square root of the unconfined compressive strength of rock appears to reasonably capture the measured shaft friction. Note that shaft movement in siltstone layer was not fully mobilized as maximum pile head settlement was still less that 1% of the pile diameter.INTRODUCTIONExtensive research of bored pile construction in soft soil in Thailand and Myanmar (Boonyarak et al., 2016; Aye et al., 2015) has been carried out. However, behavior of bored pile in weak rocks such as sandstone and siltstone is still not fully understood. Unit skin friction and unit end bearing of piles in these weak rock were reported by Horvath et al. (1983) and Pells and Turner (1980), respectively. Further research is still required to minimize variation in data presented in their study.This paper presents interpretation of load testing results of instrumented piles. These piles were excavated in aeolian deposit in the Northeast Thailand. Some piles were socketed in sandstone or siltstone. Analysis results of load-settlement, shaft shortening, pile settlement estimation, factor for calculating shaft friction and end bearing are reported. Discussion and explanation of pile behavior in sandstone and siltstone is provided.BRIEF INFORMATION OF THE PROJECTProject locationsThe construction sites are located in Khon Kaen and Nakhorn Ratchasima Provinces in the Northeast Thailand. Bored piles in this project were designed for supporting elevated structures for railways, overpasses and U-turn bridges for vehicles. These overpasses and U-turn bridges are distributed along the existing railways with the distance of about 180 km."

Jan 1, 1900

By Silas C. Nichols, Jennifer E. Nicks

"Limit states design (LSD), or load and resistance factor design (LRFD), is a method to account for the uncertainty in loads and resistance through a reliability calibration that requires all applicable limit states (strength, service and extreme) to be checked during foundation design. LRFD has been in use internationally for several decades; however it wasn’t until recently that engineers working on highway projects were required to use the method for the design of highway bridges and other appurtenances. Although the bridge community has been using a form of limit states design for structural components since the early 1970s, the design of foundations for bridges, walls and other geotechnical features had long been performed using allowable stress design (ASD), whereby all uncertainty in loads and material resistance is combined in a single factor of safety. While the move to LRFD was viewed as a more rational approach for the design of bridges and structures, the transition to its use for geotechnical engineering has been met by many with confusion and difficulties in application. This article will revisit the history of transition from ASD to LRFD for geotechnical engineering, summarize the status of the transition and issues with its use, and briefly discuss some emerging research opportunities for improving and advancing the design platform.Background and HistoryUntil about a decade ago, foundations and substructures for bridges were traditionally designed using ASD, while the superstructure was designed using load factor design (LFD), a precursor to LRFD that incorporated factored design loads but no risk assessment. This combination led to uncertain and incompatible safety margins in design for the various bridge components. In 1986, the American Association of State Highway Transportation Officials (AASHTO) Subcommittee on Bridges and Structures (SCOBS) concluded that the standard bridge specifications in use at the time for U.S. transportation projects had significant inconsistencies and gaps, wasn’t up to date with emerging technology and that the development of new specifications was warranted. The proposed solution by the subcommittee was to transition to a more coherent method of design where applicable failure and serviceability conditions could be evaluated considering the uncertainties associated with loads and resistance."

Jan 1, 2015

By Michael G. Batten, Brian D. Keaney

]The Virginia Department of Transportation (VDOT) and the harbors on the James River routinely use precast concrete piles founded in the Yorktown formation to support bridges and other coastal structures. However, axial pile resistances for large diameter piles in this area have been historically overestimated on past projects. This may be due to a common assumption that very large unit end bearing resistance will be developed for a large diameter displacement pile that is driven a significant depth. This assumption is integrated in the Nordlund (1963; 1979) method which is commonly used to estimate axial pile resistance for bridge foundations. A static and dynamic pile load testing program was implemented as part of the Hampton Roads Bridge and Tunnel Expansion project in Norfolk, VA in the James River. A primary objective of this program was to calibrate an axial resistance calculation method against the measured load test results. A method developed by Eslami and Fellenius (1997) that uses CPTu data directly was effective at calibrating to the measured load test results, and allowed for clearer interpretation of the unit resistance values than indirect, semi-empirical methods that require interpretation of soil friction angle and undrained shear strength.

Sep 8, 2021

By Zhang Wengang, L. John Endicott

The properties of many geological materials are variable. This is especially true for variations in elevation of the top of rock profile, strength of weathered rock, and conductivity of rock masses. Often the site investigation stage is completed by site specific ground investigation utilizing boring, sampling, and testing. Statistically this is a sampling procedure, but the borings are often widely spaced, and ground conditions between borings are deduced by interpolation. Often budgets are a limiting restraint and the information that is obtained may be less than desired. Sampling and testing is often biased. If claims for unforeseen ground conditions are to be avoided, the properties of the ground should be adequately identified. This paper describes how data can be used to evaluate the subsurface top of rock profiles, and can give insight into representative, maximum, and minimum strengths, and variation in conductivity relating to inflow of water into excavations, that can assist in planning the works and also in resolution, or avoidance, of disputes about unforeseen ground conditions. INTRODUCTION The mechanical properties of the ground are naturally variable. The work of Geologists, Engineering Geologists and Geotechnical Engineers is fundamentally investigative. Frequently, budgets for ground investigation are squeezed, resulting in widely spaced boreholes, with conditions between them determined by interpolation. Profiling can be adopted but the measurement, such as seismic velocity, is used as an indirect means of computing in-situ profiles and mass properties. Often a lot of test data are generated on large projects or by many projects in the same vicinity. Published data enlarge the database for a given project, and databases can be interrogated to gain insight into different categories of ground. Integration with geological studies can then lead to more reliable characterization of the ground in terms of identifying the materials present, their extent and their range of properties. This paper focuses on properties of rocks that are generally required for ground engineering, namely the top of rock profile, the unconfined strength of rock materials, and the mass conductivity. Data are obtained from Granodiorite and Granite in Hong Kong, and from Granite and the Jurong Series of weakly metamorphosed sedimentary rocks in Singapore. All four rock types have been tropically weathered, resulting in widely varying top of rock profiles, material strengths and mass conductivity. With a wide range in values for these parameters, project specific ground investigation conducted within a limited budget may run the risk of falling short of obtaining sufficiently reliable data sets, resulting in risk that unforeseen ground conditions may be encountered.

Jan 1, 2019

By Fabio Santillan, Lyndon Bedford

"This paper presents the main features of the Wolf Creek Dam Foundation Remediation Project, highlighting the innovative construction approach and stressing on how the collaboration between the contractor and the owner became a key element for the success of this project.The main rehabilitation contract, $341 M, was awarded in 2008 for the construction of a 980,000 sqft concrete barrier. Most of this 2ft-wide concrete barrier wall is being built to depths reaching 277 ft using innovative construction techniques proposed by the contractor and under quality control measures that exceed by far the industry standards.The construction of the barrier wall entails the use of nine different foundation techniques which run concurrently following very stringent requirements in terms of verticality, distance between open elements, strength, permeability and dimensions that control the installation sequence of each barrier wall element.The innovative construction approach by the contractor and the collaborative efforts by the contractor and the USACE (“US Army Corps of Engineers”) have brought this unique and very difficult project to a successful completion, setting new standards in the dam foundation industry and nine months ahead of scheduleINTRODUCTIONWolf Creek Dam is on the Cumberland River in south central Kentucky. It provides hydropower, flood control, water supply, and water quality benefits for the Cumberland River system and surrounding region. The lake is a source of recreation that has attracted more visitors (4.89 million) than Yellowstone National Park (2.87 million).The dam and its adjacent reservoir reside upon a heavily Karst bedrock foundation. In late January 2007, the USACE placed the dam under a 'high risk' for failure designation. As a temporary measure, the pool elevation was lowered to 680 ft Above Main Sea Level (“AMSL”), 80 ft below its maximum capacity, with huge impacts to the local economy while the major, and ambitious, $ 594 million remediation program to bring the dam back to its full operating condition was carried out.The main rehabilitation contract of $341 million was awarded in 2008 for the construction of a 980,000 sqft concrete cut-off barrier. Most of this 2ft-wide concrete barrier wall has been built to depths reaching 277 ft using innovative construction techniques under quality control measures that far exceed the industry standards."

Jan 1, 2015