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By Dennis Nottingham

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

Jan 1, 2004

By Donald Deardorff

Helical piles often rely on the final installation torque for ultimate capacity verification. When helical piles are designed using traditional bearing capacity equations for deep foundations and field monitored for a specified final installation torque, a factor of safety equal to 2 is often allowed for the design. One of the more common methods of determining torque during helical pile installation is by correlating the differential pressure across a hydraulic gear motor to a torque. Most drive head manufacturers provide multipliers to convert differential pressure to torque for different drive head models. These multipliers are based on theoretical torque equations and vary with the planetary gear ratio, hydraulic gear motor displacement and drive head efficiency. Drive head manufacturers show a linear fit between the differential pressure and output torque with no scaling effect. Previous drive head testing performed by the author has confirmed that the drive head differential pressure to torque relationship is generally linear however there is a scaling adjustment needed. This results in a variation of multipliers across the differential pressure range for a given drive head. Eight hydraulic drive heads from three manufacturers were field tested by Foundation Supportworks, Inc. to compare the torque versus differential pressure curves with varying installation equipment, hydraulic line sizes and hydraulic flow rates. Differential pressure was monitored using three methods including pressure gages, PT-Tracker and an Ashcroft AT-100. Flow and temperature was measured using a Webtech system analyzer. Torque was measured using a Pro-Dig in-line torque transducer, a TruTorque indicator and a Chance Mechanical Dial in-line torque indicator. The current testing indicates that a change in installation equipment and/or a change in hydraulic flow rate may affect the torque versus differential pressure curve of a given drive head. The results of this testing also show that some of the methods for determining torque during helical pile installations may be unconservative, thereby resulting in safety factors less than required.

By Donald Deardorff

"Helical piles often rely on the final installation torque for ultimate capacity verification. When helical piles are designed using traditional bearing capacity equations for deep foundations and field monitored for a specified final installation torque, a factor of safety equal to 2 is often allowed for the design. One of the more common methods of determining torque during helical pile installation is by correlating the differential pressure across a hydraulic gear motor to a torque. Most drive head manufacturers provide multipliers to convert differential pressure to torque for different drive head models. These multipliers are based on theoretical torque equations and vary with the planetary gear ratio, hydraulic gear motor displacement and drive head efficiency. Drive head manufacturers show a linear fit between the differential pressure and output torque with no scaling effect. Previous drive head testing performed by the author has confirmed that the drive head differential pressure to torque relationship is generally linear however there is a scaling adjustment needed. This results in a variation of multipliers across the differential pressure range for a given drive head.Eight hydraulic drive heads from three manufacturers were field tested by Foundation Supportworks, Inc. to compare the torque versus differential pressure curves with varying installation equipment, hydraulic line sizes and hydraulic flow rates. Differential pressure was monitored using three methods including pressure gages, PT-Tracker and an Ashcroft AT-100. Flow and temperature was measured using a Webtech system analyzer. Torque was measured using a Pro-Dig in-line torque transducer, a TruTorque indicator and a Chance Mechanical Dial in-line torque indicator. The current testing indicates that a change in installation equipment and/or a change in hydraulic flow rate may affect the torque versus differential pressure curve of a given drive head. The results of this testing also show that some of the methods for determining torque during helical pile installations may be unconservative, thereby resulting in safety factors less than required."

Jan 1, 2017

"1.0 DESCRIPTIONThis work consists of furnishing all necessary labor, equipment, and materials to install prefabricated vertical (wick) drains in the ground in accordance with the Plans and as specified herein.2.0 REFERENCED CODES AND STANDARDSASTM D4716-08 Standard Test Method for Determining the (In-plane) Flow Rate per Unit Width and Hydraulic Transmissivity of a Geosynthetic Using a Constant HeadASTM D4632-08 Standard Test Method for Grab Breaking Load and Elongation of GeotextilesASTM D4533-11 Standard Test Method for Trapezoid Tearing Strength of GeotextilesASTM D4491-99a Standard Test Methods for Water Permeability of Geotextiles by Permittivity (2009)ASTM D4751-04 Standard Test Method for Determining Apparent Opening Size (A.O.S.) of a GeotextileASTM 6918-09 Standard Test Method for Testing Vertical Strip Drains in the Crimped Condition3.0 QUALIFICATIONSThe Contractor shall have successfully completed a minimum of five wick drain installation projects in similar ground conditions, and installed not less than 5,000,000 linear feet (1,525,000 linear m) of wick drain in the past five years. The Contractor shall have a minimum of five continuous years of wick drain installation experience."

Jan 1, 2014

By Dileej M. Dewaikar, Poonam A. Patil

"In this paper, the ultimate lateral resistance of a long, flexible, unrestrained vertical pile in a cohesive soil is computed under static loading condition using py curves. A simple and improved method for the construction of hyperbolic p-y curves for a cohesive soil is proposed for static loading conditions. An iterative analysis is employed with secant modulus approach, using a matrix method known as moment area method developed by Sawant and Dewaikar. The loadground line displacement relationship is obtained for different load eccentricities using p-y curves developed by Matlock, Georgiadis et al. and the proposed hyperbolic p-y curves for different eccentricity ratios. These values are compared with the values computed from model test performed by Rao et al. and with the limit equilibrium solution given by Broms. The comparison shows that, the results obtained using hyperbolic p-y curves shows a better agreement with the model test data with the maximum difference within 15% using other methods; whereas Broms' limit equilibrium solution shows some agreement with the results based on Matlock's p-y curves.INTRODUCTIONPile foundations are used for jacket type offshore structures, which are subjected to large magnitudes of lateral loads due to lake or ocean waves, winds and ice forces. The failure of a pile-soil system is catastrophic and excessive deflection of the pile creates operational difficulties. In the view of this, bending moment in the pile is required to be predicted in a rationar manner. The p-y concept developed by Reese and Matlock (1956) is popularly being used to estimate the pile top deflection and bending moments.The ultimate lateral load which causes collapse of a pile-soil system is generally estimated using Broms' (1964) method, which is based on limit equilibrium considerations. The p-y curves are basically nonlinear in nature and include ultimate pressure at the depth where they are generated. Therefore, if the lateral deflection of pile top against different magnitudes of lateral load is obtained, it should be possible to obtain the ultimate lateral load from this load-deflection relationship."

Jan 1, 2005

By W. Morgan NeSmith

Drilled displacement (DD) piles often develop significantly larger unit shaft resistance values than other drilled or augered pile systems in coarse grained materials. Minimal vibration and limited spoil development are also associated with DD pile installation and these factors are frequently additional financial and/or environmental benefits of the system. The application of DD piles in North America dates to the mid-1990s and their use in the Midwestern United States has been significant, particularly in the past 10 years. The authors have collected an extensive database of DD pile performance in the United States. The alluvial and glacial deposits of the Midwestern U.S. provide conditions where drilled displacement piles perform very efficiently when compared to coastal and residual geologies. This paper presents a summary of the authors? experience regarding installation and performance of DD piles in the Midwestern U.S. Information presented includes summary presentations of DD performance across a range of site conditions as well as a discussion of the relationship of DD performance and installation effort in the Midwest as compared to other geologic settings in the U.S.

Jan 1, 2009

By David White

When finished (projected completion in 2016) the Hong Kong-Zhuhai-Macau Bridge Project will comprise three cable-stayed span bridges and a 4.15 mile immersed tube tunnel - linking Hong Kong to Macau and the mainland Chinese city of Zhuhai. The design included two artificial Islands to serve as the transition structures for the tunnel to bridges, entailing a massive seaborne land reclamation project, and the use of thousands of sheet piles, and man-hours. The challenges of driving individual steel sheet in 100? of water are well known, let alone in the open waters of the South China Sea. In 2010 a joint effort between American Piledriving Equipment (APE) and Allnamics Pile Testing Experts convinced the Chinese contractor First Harbor Marine Group China that a massive multi-vibro hammer can be used to drive 130? long, 72? diameter steel pipe piles weighing 662 US tons each into the sea bed of the South China Sea for the Hong Kong - Zhuhai - Macau bridge artificial islands. Combining APE?s hammer design, production and operation know-how with the pile driving simulation and installation know-how of Allnamics made it possible to show the feasibility of driving these gigantic piles into bottom of the sea to the required depth.

By David White

"When finished (projected completion in 2016) the Hong Kong-Zhuhai-Macau Bridge Project will comprise three cable-stayed span bridges and a 4.15 mile immersed tube tunnel - linking Hong Kong to Macau and the mainland Chinese city of Zhuhai. The design included two artificial Islands to serve as the transition structures for the tunnel to bridges, entailing a massive seaborne land reclamation project, and the use of thousands of sheet piles, and man-hours. The challenges of driving individual steel sheet in 100’ of water are well known, let alone in the open waters of the South China Sea.In 2010 a joint effort between American Piledriving Equipment (APE) and Allnamics Pile Testing Experts convinced the Chinese contractor First Harbor Marine Group China that a massive multi-vibro hammer can be used to drive 130’ long, 72’ diameter steel pipe piles weighing 662 US tons each into the sea bed of the South China Sea for the Hong Kong - Zhuhai - Macau bridge artificial islands. Combining APE’s hammer design, production and operation know-how with the pile driving simulation and installation know-how of Allnamics made it possible to show the feasibility of driving these gigantic piles into bottom of the sea to the required depth.INTRODUCTIONThe challenges of driving individual steel sheets in deep water are well known, let alone in the open waters of the South China Sea. Often the challenges of construction are overcome with engineering or equipment. The challenges of China’s Hong Kong-Zhuhai-Macau Bridge, on the drawing board since 1983, were to overcome both. The challenges of overcoming the skepticism of the Chinese Engineering community would be another story.The finished project will comprise three cablestayed span bridges and a 4.15 mile immersed tube tunnel linking Hong Kong on an eastern span to the China mainland cities of Zhuhai and Macau via two western spans."

Jan 1, 2017

By George Burnhart

"Sonic drilling is a relatively new technology even though it has been in development since the late 1940s. It was initially funded by the U.S. petroleum industry and then, in the late 40s, Russian scientists worked on developing sonic drilling, their interest based on drilling rates 3 to 20 times that of conventional methods. In the early 1960s, the Shell Oil Company backed research that resulted in a down-hole device with a series of eccentric weights driven by drilling fluid to generate vibration. Hawker Sidley, in the early 1980s, developed the first modern prototype sonic drills in Vancouver B.C. and the North Star Drilling Company in Minnesota became the first contractor in the U.S. to operate sonic equipment in 1985. In 1994, North Star became a division of Boart Longyear, headquartered in Salt Lake City, Utah.What’s Unique about a Sonic DrillA sonic drill rig appears and operates very much like any conventional top-drive rotary rig. The key difference is that a sonic drill has a specially designed hydraulically powered drill head, containing oscillators, that generates adjustable high-frequency vibratory forces. The sonic head is attached directly to the drill pipe or outer casing, sending the high frequency vibrations down through the drill steel to the face of the drill bit. This creates displacement, fracturing or shearing action depending on the material being drilled. The oscillator uses two eccentric, counter-rotating balance weights or rollers that are timed to direct 100% of the vibration at 0 degrees and 180 degrees. An air spring houses the oscillators and separates the vibration from the drill rig itself. The vibratory frequency is controlled to suit operating conditions and to achieve optimum drilling rates.When the vibrations coincide with the natural resonant frequency of the steel drill rod or casing, a natural phenomenon called “resonance” occurs. It allows the rig to transfer timed vibratory energy into the top of the drill string, utilizing the natural stored energy of the steel. This causes the drill string to use inertia and act like a flywheel delivering tremendous amounts of energy directly to the bit face. In friendly overburden formations, a sonic drill rig can achieve penetration rates of one ft per second."

Jan 1, 2008

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

By Jørn Thomsen, Christoffer Brodbaek

"As governments increasingly accord high priority to sustainable energy, policymakers are finding that wind energy has a long track record as a proven alternative to conventional energy supply.Over the past two decades, wind turbine projects have been constructed offshore because of more stable offshore wind conditions and because there is more available space for large wind farms out in the open sea. Vindeby Wind Farm in southern Denmark was constructed in 1991. As the world’s first offshore wind farm, it provided valuable information and experience for researchers and designers that have led to new technologies and design improvements, a trend that will continue as more offshore wind farms are constructed. Today, the world’s capacity of the installed offshore wind turbines exceeds 1,000 MW. Most of these are installed in Northern Europe where there was early political support and favorable conditions, such as strong winds and relatively shallow waters. Offshore wind projects are now under development around the globe, including continental Europe, the U.K. and North America. ‘The largest offshore wind farm today is Denmark’s Nysted Offshore Wind Farm, which has a total capacity of approximately 480,000 MWh, equivalent to the yearly consumption of 120,000 households. It is five to six miles offshore in the Baltic Sea in the southern part of Denmark.The owner is a joint venture between DONG Energy of Denmark and E.ON Sweden. Bonus Energy (now Siemens) supplied the wind turbines, and P. Aarsleff A/S and subcontractors supplied the foundations. The contractor’s consultant, COWI A/S of Denmark, developed and designed the turbine foundations. With a total capacity of 165.6 MW, the project consists of 72 Bonus 2.3 MW turbines in water depths up to 33 ft. The turbines have a hub height of 226 ft, and the turbine blade diameter is 270 ft. The rotor and nacelle (the structure that houses the generator, gearbox and other equipment) weigh approximately 150 tons, and the weight of the steel tower is approximately 130 tons. The wind farm site is located in a relatively protected area of the Baltic Sea, but during the winter months, the water often freezes and the foundations needed to be constructed to resist ice forces. The founding soils at the site are overconsolidated clay tills with boulders and with a thin layer of softer surface sediments. Pockets of up to 30 ft of soft sediments were encountered, which required special foundation preparations."

Jan 1, 2009

By Pratter P., Boley C.

Polymers are well established in geotechnical applications, for example in ground improvement, where the polymers act as a binder that, when cured, holds the grains together by adhesive and cohesive forces. The subject of this research work is an innovative composite of polymers and gravel, which differs from conventional grouting materials due to its adjustable material properties. With these specific properties, the semi-rigid material can be optimally adapted to the local ground conditions and the individual framework conditions of a construction project. For the characterization of the composite material, stateof- the-art methods, such as image processing by segmentation, are presented. Segmentation is suitable for quality assurance and monitoring of laboratory samples and soil samples directly from ground improvement on the construction site. The load-bearing capacity of the innovative material can even be increased to the order of magnitude of concrete. For this reason, the soil mechanical laboratory tests in this research had to be modified and even expanded by rock mechanical laboratory tests. Based on the experimental investigations, the importance of this innovative material for practical application is demonstrated by a calculation example from construction practice, which shows that even difficult ground conditions can be handled with it.

May 1, 2022

By Tae Hwan Lee, Jun-Shin Lee, Daejin Kwag, Sangchul Bang, Gerard T. Houlahan, Moo Sung Ryu

"Geotechnical engineers have been installing innovative, permanent underwater foundation systems utilizing suction buckets for the offshore industry since the early 1980s (Senpere and Auvergne, 1982). This foundation system has been successfully used on numerous and various types of offshore structures in a wide range of environments. Suction buckets have numerous advantages compared to conventional underwater foundation systems. The more notable advantages include easy installation, large loading capacity, low noise and retrievability. The application of reduced water pressure inside the bucket facilitates the installation of the suction buckets, where a suction pump attached at the top of the bucket can accomplish the entire driving operation. Because of this efficient operation, very large suction buckets can be driven into the seafloor, which eliminates the use of a large number of small piles.In Korea, one of the most economical and reliable renewable energy sources is wind power; however, onshore wind power generation has encountered many problems, such as the lack of favorable sites and public concerns about noise and environmental damage. Consequently, offshore wind power generation has attracted increasing attention due to its abundant potential, high efficiency of grid connection, and availability of easy expansion.In November 2011, the government of Korea announced a national offshore wind power development roadmap, which targeted its offshore wind power generation with the goal of becoming one of the top three nations in the world for offshore wind power generation. Korea Electric Power Corporation Research Institute (KEPRI) is the main research arm of the Korea Electric Power Corporation (KEPCO) and conducts research and development on electricity, power generation, renewable energy and other energy-related matters. KEPRI ultimately provides forefront knowledge and leadership to KEPCO with respect to energy and related areas for its near- and long-term needs. Financial support for the overall project, of which the suction bucket foundation system installed for the pilot phase wind turbine is described below, was provided from the New and Renewable Energy Program of the Korea Institute of Energy Technology Evaluation and Planning funded by the Korean Government Ministry of Trade, Industry and Energy."

Jan 1, 2017

By Charles M. Wilk

"Mass stabilization involves mixing binding agents into marginal or contaminated soil to improve the subject material’s physical and/or chemical properties. This paper concentrates on the principles of soil mixing and benefits and application to new and existing rail right-of-way. Successfully applied in Scandinavia and other European countries, the soil mixing is now being applied in right of way in the northern latitudes of the U.S. and Canada. These regions have significant areas of “peaty” soils that can complicate construction and maintenance of rail and structure foundations. Mass stabilization can be used to improve the bearing strength of these soft soils for subsequent construction of railroads, pipelines, roads, and buildings. In civil engineering, the technology is often used to improve the construction properties such as bearing strength, of a marginal soil. In environmental engineering, stabilization is remediation treatment technology that protects human health and the environment by immobilizing hazardous constituents within the treated material. . The treatment is conducted while the subject material remains in-place (insitu). Mass Stabilization is often used to accomplish both civil and environmental purposes on the same project effectively addressing marginal soil while eliminating the expense of soil removal and replacement. This paper presents the principles of mass stabilization technology, implementation in the field and recent completed railway projects. The example rail projects will present the various benefits that soil mixing provides to railway construction and maintenance. Bench-scale studies and full scale implementation as well as soil construction properties before and after mass stabilization will be discussed. The paper and presentation will include information on the advantages of mixing methods and binding agent delivery systems.INTRODUCTIONNew or existing railroad right-of-ways may cross ground with low bearing capacity. Right of way subgrade undergo deflection (strain) as loads (stress) are applied. The amount of strain or deflection of the subgrade caused by loading of a train is proportional to the stiffness of the subgrade materials. Some soils, such as tamped ballast, are very stiff and resist loads well. Other soils such as soft clay, peat, or loose sand have low stiffness and undergo substantial movement under loads. It is very desirable to have the stiffest possible material in a track subgrade. Stiff subgrade material limits deflection under load, reducing track roughness and occurrence of track defects. Mass stabilization is a geotechnical method that can be used to improve the bearing capacity or stiffness of soil in these right-of-way. Mass stabilization involves mixing binding agents into soil subject to treatment while the soil remains in-place or insitu. Variations in the design or areas subject to treatment can be used to address transmission of vibration to adjacent structures."

Jan 1, 2015

By Tae Hwan Lee, Jun-Shin Lee, Daejin Kwag, Sangchul Bang, Gerard T. Houlahan, Moo Sung Ryu

"Geotechnical engineers have been installing innovative, permanent underwater foundation systems utilizing suction buckets for the offshore industry since the early 1980s (Senpere and Auvergne, 1982). This foundation system has been successfully used on numerous and various types of offshore structures in a wide range of environments. Suction buckets have numerous advantages compared to conventional underwater foundation systems. The more notable advantages include easy installation, large loading capacity, low noise and retrievability. The application of reduced water pressure inside the bucket facilitates the installation of the suction buckets, where a suction pump attached at the top of the bucket can accomplish the entire driving operation. Because of this efficient operation, very large suction buckets can be driven into the seafloor, which eliminates the use of a large number of small piles.In Korea, one of the most economical and reliable renewable energy sources is wind power; however, onshore wind power generation has encountered many problems, such as the lack of favorable sites and public concerns about noise and environmental damage. Consequently, offshore wind power generation has attracted increasing attention due to its abundant potential, high efficiency of grid connection, and availability of easy expansion.In November 2011, the government of Korea announced a national offshore wind power development roadmap, which targeted its offshore wind power generation with the goal of becoming one of the top three nations in the world for offshore wind power generation. Korea Electric Power Corporation Research Institute (KEPRI) is the main research arm of the Korea Electric Power Corporation (KEPCO) and conducts research and development on electricity, power generation, renewable energy and other energy-related matters. KEPRI ultimately provides forefront knowledge and leadership to KEPCO with respect to energy and related areas for its near- and long-term needs. Financial support for the overall project, of which the suction bucket foundation system installed for the pilot phase wind turbine is described below, was provided from the New and Renewable Energy Program of the Korea Institute of Energy Technology Evaluation and Planning funded by the Korean Government Ministry of Trade, Industry and Energy"

Jan 1, 2017

By Maurizio Siepi, Paul van Horn, John Coupland, Julian Crawley

"TTMJ is the acronym for the Slurry (Diaphragm) Wall Tension Track Milled Joint currently in development as part of the European Union's innovative and far-reaching Horizon 2020 initiative (FTI Pilot-2015-1 720579). The TTMJ Project has been specifically set up to deliver this versatile new step-forward in Slurry Wall technology. The TTMJ System is protected by patent in Europe and the USA, and is currently under development by a consortium comprising Trevi SpA (Italy), Arup (Netherlands) and CCMJ Systems (UK). The principles of the TTMJ System together with the installation process are herein described in general terms. The system is still under development with field trials scheduled for early 2018, so some of the detail will not be disclosed at this stage. It is the intention of the Authors that the results of these field trials and a more complete description of the System will be presented in a paper we intend to submit for the DFI/EFFC International Conference on Deep Foundations and Ground Improvement to be held in Rome, Italy in June 2018. The final section of this paper explains how the TTMJ system can be applied to a common application of slurry wall construction; deep circular or multi-cell shafts. The system can be used to construct shafts more easily and at less cost than current methods. It also allows shafts with smaller internal dimensions to be constructed than is currently practical.INTRODUCTIONCCMJ Systems (UK) realised that an innovative new approach to forming joints in both Slurry (Diaphragm) Walls and Secant Pile Walls would provide greatly improved joint integrity to greater depths, to the overallbenefit of retaining wall quality, across the world-wide foundations industry.In particular this new system is designed to:??Increase the effective depth range of Slurry Walls (especially walls excavated by grab) and Secant Walls??Remove the requirement for Stop-ends or Joint Formers??Allow for a Shear Key at the joint??Allow for a Water Stop to be installed at the joint??Permit Continuous Reinforcement across the joint??Optimise Reinforcement Density and hence Concrete Flow??Facilitate joints in corner panels eliminating the need for “L” shaped cages and reducing largesingle-pour concrete volumes and slurry storage capacity requirements.??Enable the construction of smaller-dimensioned square and circular deep shafts (especially useful for city-centre sites) than is possible with current methods.CCMJ Systems approached other industry specialists with a view to forming a development team to explore the possibilities for this new technique."

Jan 1, 2017

By Miguel E. Ruiz, America L. Fernandez, Miguel A. Pandon

"Post-grouted drilled shafts (PGS) are a deep foundation system in which grout is injected at high pressure throughout the tip after the drilled shaft has been installed. Pressure grouting of drilled shaft tips can significantly increase the ultimate capacity and stiffness of drilled shafts. Conventionally constructed drilled shafts usually require higher axial deformation to develop the available side friction and the tip resistance simultaneously. They also tend to have higher tip compressibility and reduced end bearing capacity due to disturbance at the bottom of excavation during drilled shaft construction. PGS foundations have been found to be a cost-effective solution to compensate for this capacity reduction and/or compressibility increase. PGS construction procedure counterbalances tip compressibility and end-bearing capacity reduction. The tip grouting also has a pre-stressing effect over the shaft side friction since the drilled shaft tends to move upwards during the pressure grouting of the tip. After grouting, a bulb tends to form at the pile tip pre-compressing any disturbed material and, in certain cases, increasing the tip area, thus increasing shaft tip capacity.PGS load-settlement predictions using a load transfer approach are presented in this paper and compared with corresponding load test data. The paper also presents the main findings of load transfer analyses that were carried out to investigate the potential different factors that may be contributing to the observed improved performance of PGS over conventional drilled shafts. Results show that the two main factors, that may have a significant contribution on the overall performance of the foundation by increasing its ultimate capacity at any given level of settlement, are the stress-reversal of the skin friction and the formation of a grout bulb at the tip. The grout bulb tip contributes primarily through the increased tip area and to a lesser extent through increased stiffness and strength of the soil in the vicinity of the pile tip."

Jan 1, 2005

By Melissa S. Beauregard, Randall A. Pietersen

This study focuses on quantifying the effects of water infiltration on a full-scale energy pile system’s ability to meet the thermal demand of an HVAC system. Theoretically, an energy pile system should increase its thermal capacity after a rain event due to increased moisture content creating an increase in thermal conductivity of the surrounding soil matrix. The United States Air Force Academy has an energy pile research site consisting of 8 full-scale energy piles located below a shower facility. The local colluvium surrounding the piles allows for relatively high water infiltration during rain events. This study uses an 11kW Precision Geothermal Geocube to apply a thermal load on two single-loop piles. A weather station located south of the structure records atmospheric conditions. Results indicate that moderate rain events can caused up to a 23% increase in the system’s thermal exchange capacity. This change is due to the increase in moisture content near the surface, which penetrates to deeper soil layers with time. The time required for moisture to penetrate to greater depths and then dissipate in the soil matrix, explains why increased system performance is seen for over a week following the passing of a singular rain event. 1 INTRODUCTION With a “future-forward” focus, there is an ever-pressing economic and environmental need to use sustainable sources to meet growing energy needs. HVAC is typically responsible for 34% of the overall energy required by commercial buildings and 48% of the energy required by residential buildings (USEIA, 2009; USEIA, 2012). Energy piles are a low cost, sustainable technology that have been used to offset this energy demand incurred by a building’s space heating and air conditioning requirements. An energy pile consists of heat exchanging elements in a closed loop system integrated into a building foundation and connected to a ground source heat pump (GSHP). It is most common for these heat- exchanging elements to be constructed within a drilled shaft foundation due to both construction practices and geometric considerations. This system operates based on the principle that at a certain depth below ground (typically 4 meters) subterranean temperature remains constant at a value equal to the mean annual air temperature at a given location (Kavanaugh et al., 1997). This allows the soil to function as a heat sink for cooling operations and a heat source for heating operations when exchanged within this zone of relatively constant temperature. For the past 25 years, the implementation of energy pile technology in public, residential, and even large-scale architectural complexes has slowly expanded which has created an increase in research into the topic as a result (Brandl, 2006; Hamada, 2007; Sekine et al., 2007; Gao, 2008; Bourne-Webb, 2009; Stewart and McCartney, 2013; Murphy et al., 2014). When pile construction takes place beneath the groundwater table, soil is under fully saturated conditions, maximizing thermal exchange for a GSHP system. Under unsaturated conditions, however, changing moisture contents change thermal conductivity values in a soil, which affect a GSHP system’s ability to meet a thermal demand. The observational data presented in this paper apply to GSHP systems in unsaturated soil conditions.

Jan 1, 2019

By W. L. Chong

For a project located in Docklands Victoria, a high-rise development was proposed where the geology comprised soils of various compositions and consistencies to approximately 50m deep before being underlain by a siltstone bedrock. Due to the structural loads and spatial constraints, the majority of the foundation piles were designed to be socketed into the siltstone. Key factors in selecting the Continuous Flight Auger (CFA) technique as an effective piling solution are explained. These factors included structural and geological considerations, piling rig capabilities, pile testing regime to verify load performance and integrity, the extensive suite of construction quality controls and instrumentation records required while also achieving an appropriate piling budget and program. This paper also described how these factors underpinned the design approach of the final piling scheme. Critical aspects considered during construction and post-construction quality and pile testing records required to meet and satisfy the strict project piling specifications are also presented. The project adopted what may be considered the “best practice” in deep CFA piling. To the author’s knowledge, this project achieved the record for the deepest CFA piles in Australia where multiple piles to 53.8m deep were constructed.

Nov 1, 2022

By Brian W. Wilson

A case study is presented that describes the design and implementation of a combined blast densification and deep dynamic compaction program which was undertaken to improve the foundation soils for a proposed tailings dam raise in Ontario, Canada. Based on the results of the geotechnical investigation it was determined that the foundation of the dam would be situated on tailings of both variable thickness and density, much of which would be susceptible to liquefaction under the design earthquake for the region and type of facility. Blast densification trials were completed by the owner and the results of these made available to prospective tenderers in response to a call for a fixed price contract for the design and implementation of a densification program for approximately 800,000 m3 of foundation tailings. The variation in tailings gradation and the impacts of such on the ground improvement program are discussed, as are details of both the additional blast densification field trials completed by the contractor, and the selected blast pattern and explosive charging used for production blasting. The applicability of the various ground improvement techniques to the actual conditions encountered, and the results obtained are also discussed.

Jan 1, 2010