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By Richard A. Forth

During the construction of the Island Line (ISL) in Hong Kong between 1982 and 1986 piled foundations of a building were encountered in a tunnel drive. As the tunnel alignment could not be changed work was temporarily suspended whilst grouting took place beneath the pile cap. The tips of the piles were then cut off. The normal precast concrete lining segments were replaced by the "stiffer" spheroidal graphite iron segments and tunnelling resumed. Settlement of the building was found to be under 10 mm due to the tunnel drive and no damage was reported to the building.

Jan 1, 2002

By Steven R. Musselman

The bending strength and flexural stiffness of a micropile at its threaded connection is less than its intact strength and may fail due to thread slippage or by fracture through the pin (reduced cross-sectional area of male threads in the threaded zone of the casing). The mode of failure depends on the reduction in cross-section necessary for machining the threads, and details of the threaded connection such as the length of threaded connection, size and shape of threads, and the thread density (threads per inch). Based on data from bending tests conducted on 9-5/8 inch diameter micropile casing, a method has been developed to predict the ultimate moment capacity and initial bending stiffness of round threaded micropile connections. Two modes of failure were observed from four-point bending tests conducted at the University of Illinois on 9-5/8 inch casing with round threads. Threaded micropile casing connections with an effective thread length of 1.35 inches typically failed by slippage at the threads (jump out), while connections using an effective thread length of 1.89 inches failed by fracture of the pin. These two failure modes were described by W.O. Clinedinst in his report to the American Petroleum Institute on tension tests of threaded pipe casing. Clinedinst developed an empirical formula to determine the tensile strength of threaded connections. A method to predict moment capacity for threaded micropile connections by modeling the micropile cross-section and applying Clinedinst?s equation to determine the max tensile stress along the threaded connection while satisfying force equilibrium is proposed. The predicted moment capacity for threaded connections using this approach is within ten percent of measured for both modes of failure observed from the bending tests.

Jan 1, 2007

By V. M. Troughton

Large diameter bored piles with grouted bases have been adopted for the foundations of the majority of the buildings at Canary Wharf in London's Docklands, including a deep basement car park. The piles are founded in the Thanet Sand which forms part of London's aquifer where water levels are reported to be slowly rising. A special pile test has been carried out to determine the effects of both the basement excavation and a possible long term rise in the groundwater level on the performance of base grouted piles. These effects were simulated by injecting water around the pile toe and thus reducing the vertical effective stress. In this paper the test layout and procedures are described and the results are presented. The test results showed that the reduction in pile base resistance under increased water pressures was less than predicted by conventional design methods based on vertical effective stress. The end bearing resistance was found to be proportional to the mean effective stress.

Jan 1, 1989

By Seung-hoon Lee

The use of piled raft foundations has been considered as an economical alternative to conventional piled foundations because a portion of the applied load is carried by the raft in the design of piled raft foundation. In analyzing the behavior of a piled raft foundation as a settlement reducer, an accurate estimate of settlements of the system should be made on the basis of the understanding of nonlinear behavior of piles in layered soils as well as the interaction between the raft, soils, and piles. Although the 3-dimensional finite element method and simplified analysis methods have been used for the design of piled raft foundations, these methods were found to be inadequate for the practical purpose or could not consider the interactions properly. This study developed an approximate hybrid method of analysis to be used for the practical design of piled raft foundations considering pile-soil, raft-soil, pile-soil-pile and raft-soil-pile interactions. In the presented method of analysis, the settlements of the system are estimated satisfying the compatibility of two separate models which are the flexible raft model consisting of 2-dimensional finite elements supported by springs representing soils and piles, and the group-pile model embedded in layers of soil having different properties. Comparisons with other analytical methods as well as a 3-dimensional FEM program were made to verify the sufficient capabilities of the proposed hybrid model for application to practical design and analysis of piled raft foundations.

Jan 1, 2008

By Luo Yang

It has been known that after initial pile driving, pile capacity gain over time (set-up) could constitute a significant portion of the total pile capacity. In the past, there has been very little guidance for incorporating pile set-up capacity in design. This may be due to large uncertainties involved in predicting the pile set-up. A comprehensive statistical database is developed to describe the increase of pile axial capacity with time, known as set-up, when piles are driven into sand. Based on the collected pile testing data, pile set-up is significant and continues to develop for a long time after pile installation. The statistical database shows that a lognormal distribution can be used to describe the probabilistic characteristics of the predicted set-up capacity using Skov and Denver?s equation. The main objective of this paper is to incorporate the set-up effect into a reliability-based Load and Resistance Factor Design (LRFD) of driven piles in sand. A First Order Reliability Method (FORM) is used to derive separate resistance factors that would account for different degrees of uncertainties associated with the measured short-term capacity and the predicted set-up capacity from the proposed semi-empirical equations. The incorporation of set-up effects in the LRFD helps improve the prediction of the total capacity of driven piles, resulting in more economical design. A practical design procedure within LRFD framework to incorporate the pile set-up effect is outlined at the end of the paper.

Jan 1, 2006

By Dan Brown

A method is outlined for computing the contribution of a micropile group to global stability of a sliding mass. The forces in the micropile are computed in a way which accounts for the effect of soil mass movement on the mobilization of axial and shear forces and which maintains compatibility between shear and axial force as a function of displacement. The method provides a rigorous model to incorporate the pile forces into the stability calculations, including the effect of pile forces on the resultant shear and normal forces at the sliding surface. This paper demonstrates the proposed solution using a simple example slope.

Jan 1, 2007

By Li Tiemin

It is one of important tasks in research of vibratory pile driving to increase speed of pile driving and depth of pile driving -- this means to increase capability of penetrating hard layer. In general, vibratory pile driving hammer make pile be situated in vibratory situation to drive pile by means of weight of hammer and pile, but the depth of pile driving and capability of penetrating layer are limited by dead weight of hammer. This paper introduces a new kind of vibratory pile driving hammer which differs from general ham­mer. A set of pressing system is attached to hammer and pile driving frame. The pull of winch installed on frame passing guide pulleys bring downwards press to pile through absorbing system of hammer. The practice and comparison test have showed that the new hammer is faster in pile driving and bigger in capability of penetrating layer than general one. Now, the vibratory pile driving hammer with pressing device has been applied widely in China. RESUME: The vibratory pile driving hammer based on vibratory principle to design have applied wide­ly in foundation engineering in many countries over the world. In order to suit the needs of deep foundation, at present, how can quicken speed of pile driving and increase depth of pile driving have become even more value to many countries in the world. This paper introduces a kind of rapid vibratory pile driving hammer which can drive pile deeper and more faster comparing with common vibratory pile driving hammer. Therefore, a kind of simple and reliable method has been offered for rapid vibratory pile driving in deep foundation.

Jan 1, 1991

By J. Nakayama

For installation of round steel piles or cast-in-place pile construction through boulder contained ground or rocky formation, usual system does not function properly or impossible to work. This paper introduces an installation system which combines unique mechanism where the drill is installed on the top of a driving round steel pile or a stand pipe which is initially driven into the overburden to the depth of self-standing. When the pile driving or bore hole drilling encounters hard strata or boulder contained ground, hard material shall be crushed by the down-the-hole chiselling operated in adjustable short stroke and high frequency of blows while cuttings are discharged in reverse circulation through central reverse pipe while round steel pile is simultaneously stroked by a hydraulic hammer. The paper shall explain the mechanism of the system and introduces construction examples for bridge foundation and piled jetty.

Jan 1, 1999

By Arturo Ressi di Cervia

Construction of the drilled shafts for the Brightman Street Bridge Replacement Project were not only challenging due to working over the water but were also challenged by changed soil conditions, concurrent work being performed by an adjacent contractor on the same project, environmental restrictions and severe winter conditions. A total of 36 x 8 feet diameter drilled shafts with 7.5 feet rock sockets were installed for the East and West bascule piers. This project also included Osterberg Cell load testing on two production drilled shafts at each the East and West bascule piers. The results from the load test program were used to fine tune the design of the drilled shaft rock sockets. From a constructability standpoint the reverse circulation drilling method with a pile top drill rig proved to be an excellent choice for drilling the overburden and rock sockets of the large diameter deep drilled shafts.

Jan 1, 2003

By Michael J. Brown

Load testing is important for controlling the quality of piled foundations. The Statnamic test is an alternative to existing testing methods with a load duration that lies between that for static and dynamic tests. Current methods of analysis offer excellent correlation between static and Statnamic tests for coarse-grained soils but often over-predict the capacity for fine-grained soils. Thus a calibration chamber is being used to produce instrumented beds of clay with reproducible properties. A model pile placed in the beds can be loaded at varying rates using a computer controlled servo-hydraulic system. Results from the modelling will be used to improve methods of analysis and govern the design of a full-scale study. Initial results suggest the rate effect can be represented by a power law relating pile velocity and resistance. Statnamic loading of the model pile produced large negative pore pressures in the clay bed.

Jan 1, 2002

By Michael P. Balducci

Urban deep foundation projects contain unique risks that must be recognized by the parties involved. Common pitfalls must be recognized and avoided or addressed through contractual relations and corresponding insurance coverage. By understanding these pitfalls, examining the risk-apportioning clauses and corresponding insurance obligations, may the parties? desires and expectations be met.

Jan 1, 2008

By Y. Z. Xu

This paper presents a new dynamic method called Resonant Pile Test (HPT) for evaluating bearing capacity of pile. The basic conception of RPT is given in brief and the measuring system is also introduced. In addition, the influences of the magnitude of exciting force and of the mass of pile cap on test results are discussed. Finally, comparisons between values of bearing capacity given by RPT and by static load tests for a variety of pile types are listed.

Jan 1, 2010

By A. K. Bhattacharya

Cylindrical bridge piers are widely used and equations exist that can predict the maximum depth of local scour around such piers. Scour around piers is an undesirable phenomenon, as it requires the foundation to be placed to a greater depth resulting in increased cost, making it worthwhile to investigate scour-reducing measures. A number of scour-reducing measures have been tried out for cylindrical bridge piers including placing a concrete collar around the pier, having a delta-wing projecting upstream in front of the pier, placing riprap around the pier, using a group of piers instead of a single pier, having a slot in the pier aligned in the longitudinal direction. The objective of this study is to investigate the effect of upstream protective piles on reduction of maximum local scour depth around a cylindrical bridge pier. The upstream piles are placed at different radial distances in front of the pier and the scour depths are observed. The proposed equation of Dey (1997) for determining the maximum depth of scour around a cylindrical bridge pier is used. The reduction of local scour around the pier is compared with local scour around an unprotected pier.

Jan 1, 2009

By Geoffrey Birch

A skilled and efficient workforce is a pre-requisite for the success of modern construction companies. The drive for improved performance, innovation and best value must be matched by the enhanced skills of the construction personnel. Training has been accepted as one of the essential cost effective elements to achieve these goals. The foundation industry demands particular specialist skills and requires focused training for its dedicated operatives. The introduction and development of specific training qualifications for the foundation sector is providing significant benefits.

Jan 1, 2000

By Ali Porbaha

The use of soil nailing technology as a cost effective alternative for excavation support and slope stabilization has substantially increased in the United States during the last decade. For example, in the past thirteen years, more than 185,800 square meters of soil nail walls have been constructed in California alone. The conventional soil nail systems pose difficulties when ground conditions are subject to caving, for instance for silty sand (sugar sand) or cobbles and boulders. The construction industry has developed self drilling hollow bar systems (or pressure injected bored, IBO) that combine both drilling, placing and grouting in a single operation as a solution to speed up construction. While the system is extensively used for temporary applications, nevertheless, some concerns, particularly about corrosion, has limited the use of this technology as a permanent system in North America. This study presents several issues related to self drilling soil nail systems, the results of a field investigation and a summary of the research project.

Jan 1, 2006

By Mark A. Willian

The purpose of this short paper is to present soil profiles and basic soils information for the portion of the I-880 Replacement Project alignment where highway structures are to be built. The information presented here is derived primarily from foundation investigations conducted by the Caltrans Foundation Unit (currently the Structures Foundation Branch, Office of Structural Foundations) and by others under Caltrans direction. The foundation investigation for the I-880 Replacement Project began in May of 1991. The field work was completed in May of 1992 and consisted of 93 rotary sample borings, 11 consolidation sample borings, 6 TEXAM® pressure meter borings, six in-place vane shear borings and 57 electronic cone penetrometer soundings.

Jan 1, 1996

By J. A. Hayes

For over a decade the Osterberg Load Cell has been successfully used to determine the shear capacities of drilled shafts. Since the test method measures side shear directly, analytical complications due to the influence of end bearing resistance are removed. The data suggest that the side shear component of a drilled shaft's capacity is often more significant than end bearing. Given the interest in the use of side shear in drilled shaft design in compressible materials, it is important to examine factors that can influence capacity. We have found that some factors widely believed to influence capacity, such as slurry type, are not as important as commonly thought in most materials. Factors that are not usually considered as important, such as casing use, hoop spacing, concrete slump, concrete additives, spacers and rebar clear cover, seem to be more influential with respect to side shear capacity. For example, substantially lower than predicted shear resistance can occur when the rebar clear cover is small with respect to the cage diameter. We observe this most often in fine-grained cohesive soils. This effect can be exaggerated if the rebar cage has tight hoop spacing, if the concrete has low slump and if the hole is not straight. We have also noted that improper use of temporary casing can have a dramatic effect on side shear resistance. In some cases we have observed tested shear capacities reduced to less than 5% of either predicted or available shear values.

Jan 1, 2003

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.

By M. J. Preim

Two case histories are presented on the evaluation of static bearing capacity of piles driven in soils that exhibit time dependent strength changes. Under consideration are a steel and a concrete pile driven into soils generally consisting of silty and clayey fine sand. Pile dynamic measurements and analyses were performed on both piles during initial installation, and also during restrike one week later. This information was used to predict each pile's long term capacity (defined as 14 days after initial drive), which was then compared to that measured with a static load test. Agreement between predicted and measured capacities were remarkably good, with an average error of only 4.5 percent. Two weeks after driving, total pile capacities were three times those at the end of drive. If only the skin friction was considered, however, it increased by an average factor of 16. The increase in pile capacity was determined to be linear over the time period considered.

Jan 1, 1989

By Aaron S. Bradshaw, Ryan M. Coulson

The offshore wind industry in the United States is slowly emerging with the recent construction of the first offshore wind farm located off the coast of Rhode Island. The turbines at the Block Island wind farm are supported by piled jacket structures, which historically have been used for much heavier oil and gas platforms. Offshore wind turbines have unique design requirements and the axial behavior of the supporting piles under cyclic loading is important to design. Cyclic degradation along the pile shaft can affect the capacity, deformation, and stiffness performance of the foundation and of the structure as a whole. This paper proposes a strain-based approach to estimate the fatigue (or endurance) limit of a cyclically loaded pile that may be applicable to long-term service loading. The method is applied to an existing load test dataset and the analysis results appear consistent with the observed pile response. INTRODUCTION The demand for renewable energy has been increasing in recent decades and wind power has seen a dramatic increase in popularity. In Europe, as of 2017 there were 4,149 grid-connected offshore wind turbines across 11 countries (windeurope.org), many of which are supported on monopile foundations. It wasn’t until recently (2016) that the first offshore wind farm was constructed in the United States off the coast of Block Island, Rhode Island. The project included 5 piled jacket structures founded in terminal moraine deposits. Future offshore wind development along the U.S. eastern seaboard could possibly utilize jacket structures in granular foundation soils. Loads from wave, wind, and turbine rotation induce cyclic loads on the foundation that have on the order of 108 loading cycles over the service life on the structure (Schneider and Senders 2010). Turbines located along the U.S. east coast have the added risk of hurricanes. As shown in Figure 1a, the lateral loads on a jacket structure are transferred primarily as axial compressive and possibly tensile loads on the supporting piles depending on the weight of the structure. The friction along the shaft of the pile can be prone to cyclic degradation, leading to reduced pile capacity and stiffness, and increased deformations. An offshore wind turbine foundation must be designed for a variety of limit states including ultimate, serviceability, and fatigue limit states. For a jacket structure this would include an analysis of the ultimate axial pile capacity, axial stiffness, and axial deformations, all of which can be affected by cyclic loading both under extreme (i.e. storm) conditions as well as long-term service conditions. Axial pile stiffness is needed, for example, to estimate the natural frequencies of the structure as a whole and to assess dynamic and fatigue loads. The structure must be designed such that its natural frequency remains outside the loading frequencies of the waves and turbine blade passing frequencies to avoid resonance. Therefore, prediction of the axial response of the piles is important to the design of these structures.

Jan 1, 2018