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By Fawad S. Niazi

Analysis of deep foundations in terms of axial capacity has been a topic of great interest in the soil-structure interaction problems. Soil behavior is governed by a series of complex stress-strain changes that occur during pile installation and subsequent loading. Owing to the difficulties and uncertainties on the basis of the soil strength-deformation characteristics, one of the most frequently followed design practice is to refer to the formulae correlating directly the pile axial capacity components of unit base resistance (qb) and unit shaft resistance (fp) to the data collected from cone penetration test (CPT), i.e. to the tip stress (qc or more proper qt), sleeve friction (fs), and shoulder pore water pressure (u2). The elementary basis for such formulations has been the idea of considering cone penetrometer as a mini-pile foundation. This has resulted in plethora of correlative relationships in the past over 60 years. Such correlations, although empirical, have been worked out on the basis of load test results from both instrumented and un-instrumented full scale piles and are able to accommodate many important variables. A quick review of the evolution process and development of such design formulations is presented with a view to propose recommendations for future research directions, where the latest version of CPT i.e. seismic piezocone test (SCPTu) can be used to advance from capacitysingularity to the complete axial pile load–displacement (Q–w) response.

Jan 1, 2013

By Stephen Darmawan, Mahdi M. Disfani, Arul Arulrajah, Alireza Mohammadinia

Deep mixing using cementitious compounds is an in-situ method of ground improvement for improving the strength, compressibility of loose sand. Artificial light cementation can increase the stiffness of loose sands significantly and reduce the settlement of loose deposits. The increase in contact area between the particles with a thin layer of cementitious agent depends on the confinement and void ratio of the soil mass. Hence, the stiffening effect of cementation not only depends on the type and amount of cementing agent and inter-particular force chain of loose deposit but also depends on the stress level at the time of cementation. In addition, the cementation effect in loose deposits can be deteriorated at relatively low strain levels. Decementation softening can cause detrimental and irreversible impacts on the soil deposit. This study investigates the effect of initial confinement and subsequently the initial void ratio at the time of cementation on small strain behaviour and decementation softening of cemented loose sand under ko loading. The effect of inter-particular contact of sand particles based on the specific surface area and also soil density was also investigated by means of shear wave propagation. This study present insightful information on effect of primary consolidation stress levels, density of soil and cementation level on softening and collapse of loose deposits improved using deep soil mixing technique. Better understanding of soil-cement interaction by optimization of binder content for deep mixing activation can lead to increasing the level of confidence in using this technique in ground improvement applications.

Jan 1, 1900

By Norm Kirk, Robert Bittner

"The addition of a new powerhouse at the existing Tulloch Hydroelectric site on the Stanislaus River in the western foothills of the Sierras Nevada Mountains of central California required a deep excavation in rock on the downstream face of the dam. A cofferdam (water exclusion device) was necessary to isolate the powerhouse construction site excavation from the existing Goodwin Reservoir and the turbulent discharge from the existing powerhouse. The cofferdam was positioned on a steeply sloping fractured rock surface exceeding 50 degrees.This paper describes the challenges encountered during design and construction of the cofferdam and describes the unique design features used to address these challenges including:•,The use of flat-sheet-piles to form cellular walls on the steeply sloping rock surface.•,The use of 5-ft deep tremie concrete plugs in the bottom of the sheet pocket cells to create the bottom seal of the cellular cofferdam walls against the sloping rock surface.•,The use of vertical post-tensioned rock anchors to provide shear resistance at the contact point between the base of the cellular-wall and the sloping rocksurface.INTRODUCTIONModification or expansion of existing hydroelectric power plants often require downstream cofferdams or water exclusion devices to temporarily separate new construction from turbulent downstream discharge of the existing dam. Most dams are positioned on solid rock in the narrowest and therefore the steepest section of the river. This combination of steeply slopingrock and the need for an exclusion barrier creates a challenge for the design engineer trying to maintain a safe dewatered construction site. Typical cofferdam solutions for hydroelectric dams usually use large granular filled circular sheet pile cells that perform as gravity structures. However, this type of structures is not well suited to steeply-sloping highly irregular rock surfaces in a confined area."

Jan 1, 2017

By Abid O. Adekunte

The design, construction and monitoring of the deep excavation support for the basement of a large-scale commercial development in Cavan, Ireland is presented. Excavation area was adjacent to existing structures and retained height H varied between 4.0m ? 11.0m. In areas where excavation depth H < 5.0m, wall was designed as cantilevered section. However in sections where 5.0m = H = 11m, additional wall supports were required for serviceability reasons. Traditionally, designers often provide additional wall support through the use of tie-back ground anchors, raking props and braces. On the current project, the main contractor was not in support of the use of temporary props so as to maximise working space, while owners of adjacent properties disapproved the use of tie-backs. The limited set-back between the wall line and site boundary also contributed to the complexity of the project. A rare alternative solution has been adopted. This novel approach involved buttressing the wall with steeply raking bored tension piles at regular intervals along the wall. Comparison of the monitored deflections in the cantilevered sections with those recorded at sections where tension piles were used shows the novel solution to be safe and quite effective. This approach is also considered to be more economical when compared with ground anchorage and propping.

Jan 1, 2008

By Uwe Hess

For the Danish landworks for the coming fixed link between Denmark and Sweden across the Øresund the focus has been on the environmental aspects of the construction and operation of the facilities. This paper describes how the environmental objectives pertaining to the project have influenced the design and construction of one of the major elements of the Danish landworks, i.e. the tunnel in Sydhavnsgade and under Sydhavn Station. The chosen construction methods for the construction pit bracing and the groundwater lowering will be described along with the observed effects on the environment as shown by simulated or measured values for noise impact, settlements, pumped groundwater and extension of the drawdown cone.

Jan 1, 1996

By Osamu Taki

The innovative Soil-Cement Mixed Wall Technique emerged in Japan and obtained recognition in the engineering and construction communities in the 1980&apos;s. This technique was introduced to the United States in 1986. It was accepted as the most credible construction technique by the U.S. Bureau of Reclamation for ground stabilization and cutoff wall work in the Jackson Lake Dam Project, Wyoming in 1987 and 1988. It was also accepted as a remediation technique by U.S. EPA for a Superfund Innovative Technology Evaluation (SITE) demonstration on in-situ solidification/ stabilization. The Soil-Cement Mixed Wall Technique consists of mixing in-place soils with cement grout or other reagent slurries using multiple axis augers and mixing paddles to construct overlapped soil-cement columns. The overlapped column panel is then extended to form an underground continuous soil-cement wall for use as a cutoff wall or a structural diaphragm wall for groundwater control and excavation support. By arranging the column panels in various configurations, the technique becomes a versatile tool for stabilization of soft or liquefiable soils.

Jan 1, 1990

By Rob Jameson

Micropiles are ideally suited to seismic retrofit applications. Their high tensile and compressive capacity can sustain the large concentrated loads induced during seismic events. Micropiles can be drilled through and grouted into the wide variety of soil and rock materials encountered in seismically active zones, using equipment that operates effectively within existing structures. Micropiles have seen increased acceptance and are now widely specified for retrofit work in the San Francisco Bay Area. While installation equipment and the structural configuration of micropiles have been largely unchanged since the early 1990?s, market forces have pressured both engineers and contractors to continually optimize the cost and performance of seismic upgrades. Instead of the contractor simply developing stronger, stiffer and cheaper micropiles as isolated structural elements in response to a specification, focus has shifted to maximizing the efficiency of micropiles within the overall foundation system. The case history of seismic retrofit project in Berkeley, CA is presented to illustrate the collaboration between designers and drilling specialist which resulted in a structurally efficient and cost effective design. The seismic retrofit program for this 6-story concrete building was developed through careful consideration of the geotechnical and structural mechanisms of resistance, in combination with the deformation response of high capacity micropiles (2670 kN) under ultimate loading conditions. This case history describes the interactive project development emphasizing performance-based design and field testing to optimize the micropile foundations and the overall structural system.

Jan 1, 2008

By Annika Gram, Teddy Johansson, Lutfi Ay

Micropiles transfer tension or compression forces as well as cyclic loads into the ground via skin friction. The Self Drilling Micropiles (SDM) can be utilized for permanent applications. The hollow bar simultaneously acts, as drilling rod, injection tube and reinforcement for the micropile. The SDM system can be used in any type of soil, including unstable soils, without the need for temporary casing. Injecting a cement grout through the hollow steel tendon ensures that the borehole is filled from the bottom to the top. The system is fast, simple, and flexible. The installation minimises noise, vibration, and spoil. There are many potential applications, including foundations, underpinning, resisting uplift, dynamic/cyclic load applications and geothermal installations. The SDM technology were introduced to India first time in the Indian history and utilised in the 4G and 5G network projects. The SDM challenge the traditional cast-in-situ piles in the 4G project and raft foundations in the 5G project. Utilisations of the tensile and the compressive strength capacity of SDM with smart solutions results in noticeably big costs, 17-38 % depending on the soil conditions and time savings. The cost of the SDM solutions was about 40% less than the cast-in-situ piles and raft foundations in an ongoing 5G project. The SDM were used successfully in the liquefiable soil types as well.

Nov 1, 2022

Pier, well cap and steining junction is a complicated 3-d re-ion. The prevalent design procedure for the pier, well cap and steining in isolated manner is not rational. In absence of an integrated approach for design of the junction structure, the well cap is designed uneconomical and at the same time pier and steining are left relatively unsafe. Strut-and-Tie Model based design is a simple solution to this problem. An example illustrating design of the junction structure using STM is presented. On comparison of the outcomes of the STM based design with the prevalent design, the following anomalies are found: i) For smooth flow of forces, length of pier at its base should preferably be made equal to the outer well diameter, ii) STM based design for the pier is more rational, economical and safe. iii) Due to presence of hoop stress, as indicated by the STM, the steining concrete in a depth of p times outer diameter of the well from the well cap level should be limited to M15 grade, iv) STM based design for the steining is more rational, economical and safe.

Jan 1, 1996

By Cassandra A. Wetzel

"Rock socketed mini-piles are a desirable foundation alternative when design capacity is more than 40 tons and there is limited access. In this case history mini-piles were designed to support between 75 and 200 kips at 12 locations adjacent to a perimeter wall, a party wall and at cast iron column piers. Limited geotechnical information, low overhead clearance, and active building population tested the creativity of the team to get the piles installed. The key geotechnical concern during installation of the mini-piles was the presence of a glacial till layer above the bedrock surface that restricted the seating of the casing into bedrock with a track mounted drill rig. Soil loss during the advancement of the rock socket using an air hammer was excessive and increased the risk of subsidence. Over a three week period the engineer worked with the contractor to modify the design, means, methods, and materials to install piles with adequate load capacity. This paper will present the changes in design and construction methods that were required.INTRODUCTIONRock-socketed mini-piles are a common and desirable deep foundation alternative to support loads more than 40 tons in New York City. Limited vertical clearance, accessibility, vibration control, and load capacity make this pile type attractive; it also does not require a static axial load test when socketed into rock. This added benefit makes this alternative all the more feasible.The installation of a drilled pipe extending to bedrock through a glacial till deposit presented challenges to the contractor and engineers to confirm the casing is seated sufficiently into the rock prior to drilling the rock socket. The loss of soil between the steel pipe and the till/bedrock interface can compromise the performance of the pile and soil loss can result in settlement of the ground surface.This paper presents the design and construction method changes made on one project during the installation of ten limited access rock socketed mini-piles."

Jan 1, 2017

By Venugopal B, M Kumaran, Thomas John, Vetriselvan A

The initial pile load tests are conducted to ensure the geotechnical capacity of the pile in a particular site condition. Normally kentledge method is adopted for the compression pile load tests. In this method the entire kentledge load is loaded above secondary beams which are supported by concrete blocks above the Natural Ground Level. So, it is important to ensure the SBC (for shear and settlement) of the natural ground. In one of our projects initially it was decided to go with kentledge system for initial compression load test on 56m long 1200mm diameter BCIS pile. The test load and total kentledge load were 2160t and 2700t, respectively. The soil strata mainly consisted of clay with low SPT N value and water table almost at ground level. It was suggested to replace top soil using Granular Sub-base (GSB) with good compaction in order to avoid excessive settlement of concrete blocks placed to support the kentledge weight. When the kentledge loading started, even before reaching 10% of total kentledge load, excessive settlement on the GSB layer was observed. This paper describes the problems faced during normal kentledge method and how it was overcome using the liner pile system for initial compression load tests in this particular site condition for higher test load.

Nov 1, 2022

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 Chul Soo Park, Juhyung Lee, Duhyun Baek

"In this study the preliminary design of suction pile as the supporting system of the concrete floating structures was performed at the offshore pilot project area in Korea. The suction pile of the floating structures has to satisfy the lateral resistance against external force evaluated from the marine and structure conditions, as well as the penetration ability according to the soil and seepage conditions. In the design, the required penetration depths for lateral resistance were evaluated with different diameters of cylindrical steel suction pile, and the design suction pressures at each penetrating depths were assessed through the comparison of penetration forces and penetration-resistances. Finally, the optimal dimension of suction pile for the pilot project area was proposed.IntroductionInterests in sea spaces have rapidly increased around the world due to limitations in use of lands. Such increase has resulted in construction of numerous marine structures aimed at expanding the use of sea spaces and developing marine resources. South Korea also needs to secure construction technologies for floating infrastructures on its relatively deep seas. Foundations for floating structures consist of anchors and mooring systems rather than driven piles or cast-in-place piles, due to limitations in equipment operation or economic feasibility. Anchors and foundations used on the sea include drag anchors and suction piles, but the suction piles are more widely used for reasons regarding uncertainties of calculation of bearing capacity and construction. Large-diameter suction piles are generally used to utilize fully their penetration ability, which is proportionate to the square of the foundation diameter, and the length-diameter ratio (L/D) does not exceed 6 (Randolph et al., 2005; Andersen et al., 2005). Recently, a design and construction technology using group suction piles consisting of medium-diameter suction piles and concrete pile caps is being developed as an alternative to the conventional large-diameter mono suction piles. In addition, pilot projects involving the group suction piles of mediumdiameter are currently being reviewed for the southwest coast area in Korea. In this study, therefore, preliminary design for installation of medium-diameter mono suction piles as the supporting system of the concrete floating structures was performed, and suction pressures, penetration forces and resistances, and lateral loading capacity with diameters were reviewed."

Jan 1, 2017

By Pancho J. Garza, Keith H. Dahlen, Chris A. Labye

"Design for reconstruction of the East Flagstaff traffic interchange project located in Flagstaff, Arizona posed particular challenges. The proposed design included construction of a nearly 50-foot tall mechanically stabilized earth (MSE) wall given rightof- way constraints and soft subgrade soils. The tight right-of-way, approximately 15 feet in certain locations, adjacent to existing structures limited the number of viable remedial alternatives to provide grade separation at the proposed bridge abutment without significant settlement. Preliminary analyses indicated the existing subgrade soils - consisting primarily of relatively soft silts and clays with decomposed pumice - would settle approximately 12 to 14 inches resulting in unacceptable wall deformation. Stone columns placed via vibratory methods (vibro-replacement) consisting of circular excavations which penetrate to firm bearing soils and which are filled with crushed stone were selected to densify the existing subgrade soils. The implemented mitigation measures helped limit settlement to less than one inch and allow for successful construction of the project. The project history - including site constraints, subsurface conditions, evaluation of remedial alternatives, stone columns methodology, and effectiveness of ground improvements - will be discussed.IntroductionThis paper describes the subsurface investigation performed for the reconstruction of the Business Route 40 (B-40) (Country Club Drive) and United States (US) 89 Traffic Interchange (TI) located within the city limits of Flagstaff, Arizona. This project is currently referred to as the East Flagstaff TI. The Project Site Vicinity Map is shown below.The former B-40/US 89 TI was considered ineffective in handling the current and projected volumes of traffic which transition from northbound (NB) B-40 to US 89 (both directions), as well as from southbound (SB) US 89 to SB B-40. The intent of the project was to reconstruct the TI to better accommodate projected traffic volumes. The project eliminated the existing ramps from both NB B-40 to SB and NB US 89. The new interchange includes a Tee intersection from B-40 to US 89. In order to accommodate this alignment, the profile of US 89 was raised several feet (on nearly the same as existing horizontal alignment) to match the elevated profile of B-40. B-40 was shifted just west of its current alignment to accommodate construction of a new, wider bridge structure which spans over Industrial Drive, the Burlington Northern Santa Fe (BNSF) railway, and old Route 66. South of the new bridge, B-40 transitioned back to the existing alignment just north of the I-40/B-40 TI. Within the project limits, both US 89 and B-40 were widened to three travel lanes in each direction."

Jan 1, 2015

By Ting Chinsu

Diaphragm wall with tie-back cable is widely used for deep excavation, especially in the area with high density of buildings. This paper presents the measured earth pressure distribution on diaphragm wall during excavation. The earth pressure cells used in field were successfully installed in deep slurry trench by a new type of simplified manipulator. The sizes of the deep excavation are 26m X 36m on plane and 9m in depth. The construction site is located between two multistorey buildings at the main business section of Beijing city. In this paper the field measurements of earth pressure distribution and the analyses based on the comparison between calculation and measurement are very valuable to improve the current calculation method for diaphragm wall design.

Jan 1, 1991

By Amr M. Sallam

A case history of utilizing a mat foundation enhanced with ?settlement-control? piles to support a high-rise building in Downtown Orlando is presented. Original geotechnical engineering studies, performed by others, recommended pile foundations due to difficult soil conditions and highly variable loads. The value engineering study performed by the authors provided alternative foundation system of the mat foundation enhanced by ?settlement-control? piles. The alternative foundation system required few iterations of structural and geotechnical analysis. A target stiffness for the settlement-control piles was selected by the structural engineer. Pile load tests were performed to verify the recommended pile geometry. A total of 81 auger-cast-in-place settlement-control piles 45-foot long 16-inch diameter were installed. A total of 24 columns were monitored for settlement, which showed substantially less settlement than predicted. It is the authors? opinion that the ?settlement-control? piles increased the mat stiffness, relieved the concentration of contact pressures around heavily loaded columns, and reduced potential differential settlement. Mat foundation with settlement-control piles provided border-line foundation solution between shallow and deep foundations and has the potential to be widely used in Central Florida for similar subsoil and loading conditions; however a thorough analysis using three dimensional Finite Element Modeling may be needed to refine the geotechnical evaluations.

Jan 1, 2009

By Shyam Chengalath, Johan Jeansson, Magnus Hörman

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

Sep 1, 2022

By Tony Suckling

The commercially available finite element program Plaxis has a key benefit over other finite element analysis programs in that it has a relatively simple user interface to input and output data. This benefit though may also be it?s weakness in that anyone, regardless of their grounding in geotechnical engineering, may use the program and produce results for design. It is essential, as for all engineering design, that the models are checked by competent engineers. This paper describes the key recurring problems found by the authors when checking Plaxis models, such as the generation of the initial in-situ ground stresses and the modelling of groundwater. Interestingly, the authors have not encountered similar problems when checking finite element models produced using other programs and conclude that this may be due to the higher calibre of modeller needed to use these other programs. The geotechnical industry is in a situation at the moment where senior managers who may not have been trained in finite element modelling are relying on less experienced staff who have had some training in modelling, either at university or post graduation. The quality of this training is variable and all organisations running easy to use programs need to be aware of the potential risks and dangers. Management procedures and engineering checks that are essential to validate the results of these models are described, assuming that those in charge are not experienced modellers themselves. The model checking process by competent persons is absolutely essential and it is hoped that this paper will help those organisations that do not have such procedures as part of their own internal Quality Assurance or design validation system. The procedures described are valid for all finite element programs.

Jan 1, 2010

By Alexander Blatt, Franz-Werner Gerressen

Power Point Presetation at DFI 2022

Sep 1, 2022

By Rudolph P. Frizzi

Structures supported on ACIP and DD piles perform successfully when quality control is maintained from the initial site subsurface investigation through pile design, bidding, and construction. The four stages of ACIP / DD pile construction are: preparation, augering the pile, grout / concrete placement, and reinforcement installation. During all four stages, careful observations and communication between the contractor and the owner&apos;s engineering inspection personnel are vital to successful pile completion. Automated monitoring equipment (AME) exists to supplement, but not replace, the field personnel&apos;s observations during the pile augering and grouting operations. Full-scale field load testing is done to verify the pile&apos;s geotechnical and structural design, and the contractor&apos;s pile installation means and methods, using several procedures including: conventional top loading, high-strain dynamic, rapid axial compression (i.e. Fundex PLT and Statnamic), and Osterberg Cell. Non-destructive sonic testing is performed to investigate the below-grade sectional properties of the completed pile; such methods include: low-strain impulse testing, and single-hole and cross-hole sonic logging. Post-construction observations are necessary to verify pile location and top properties prior to overlying cap construction.

Jan 1, 2005