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By S. Hardy

The paper describes state of the art non-linear analyses of the pile groups that were employed during the raising of the 133m high triumphal arch which forms the centre piece of the new Wembley stadium in North London. The deformation behaviour of these piles groups was critical during the lifting process, due to the slendemess of the arch structure. The issue was made more critical by the high profile nature of the project. The results of Class A (Lambe (1973)) predictions of the pile group movements are compared with observed displacements and rotations which were accurately measured on site. To illustrate the importance of soil non-linearity on pile group behaviour, comparison is also made with pile group analyses which assume a linear soil stiffness.

Jan 1, 2006

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 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 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 Zhitao Ma

The Cast-in-place Concrete thin-wall Pipe pile, referred to as PCC pile, is a new kind of pile for soft ground improvement. In this paper, firstly, the general introductions of the new pile technique, mainly including the technique principle, the structure of pile-driving machine, and the technological process were given, then based on the results of in-situ static lateral loading test, the pile lateral capacity, the relationship of load-deflection of pile at the ground surface, the lateral deflections versus depth and the soil reaction along the pile shaft were analyzed.

Jan 1, 2006

By Reinhard Gnilsen

Soil Nail walls, like any other structure, must meet high standards of design to be acceptable to the public and owners. On the other hand, the concept of soil nailing trails behind other structures in terms of defined design criteria that are commonly acknowledged. This is not to say that soil nail walls need to be less safe or less conservative than alternative more conventional concepts. Instead, the lack of established design criteria and design methodology entails that rules of thumb from past experience, overly simplified calculation assumptions, and the engineers' common sense judgement must substitute for a complex analysis of true stability and wall performance. Those "design approaches" must be conservative to ensure an adequate structure. Also, soil nailing may not be perceived prudent where site conditions are considered beyond past experience. For instance, site conditions may be perceived out-side the scope of soil nailing applicability where walls are very high, soil parameters variable or low, or nearby buildings close to the wall edge. The latter relates in particular to deep

Jan 1, 1988

By F. Castelli

A simplified non-linear method to predict the behaviour of a single pile and/or pile group under horizontal loads is presented in the paper. The evaluation of the non-linear lateral deflection is based on a procedure taking into account the decrease of the model stiffness with the increasing of the applied load. The solution derived firstly for the single pile, was extended to the case of a pile group introducing the p-multiplier (fm) concept proposed by Brown et al. (1988).

Jan 1, 2006

By Daniel J. Rider

In 1980 the Niagara Frontier Transportation Authority contracted for three miles of cut and cover box structure and station construction in Main Street, Buffalo, New York. Project depths ranged from 30 feet to 60 feet below street grade. Soils, Figure No. 1, consisted of loose to very compact sands and gravels. Ground water level was generally 20 feet below grade. Specifications required a soldier pile and timber lagging support system with external dewatering. Soldier piles were to be installed in prebored holes with bentonite slurry and lean concrete backfill. Conventional pile driving was not allowed due to concerns over excessive noise and vibrations and its effect on nearby historic structures and the surrounding population

Jan 1, 1987

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 D. V. Karandikar

Contiguous bored piles have been used in the past for retaining the sides of deep excavation. An innovative version of this method was adopted successfully in two prestigeous projects in Bombay in which in a very constricted and congested locality, adjoining seashore at Walkeshwar, 14 m deep excavations with vertical sides were required. 600 mm dia bored cast-in-situ piles were first installed at 1.2 m c/c and subsequently as the excavation proceeded, they were tied to cast-in-situ RCC waling beams. The shear connectors to the beams were pre-fixed to the pile reinforcing cage at specified depths. The pile / waling beam system was anchored into the ground by installing inclined prestressed cable anchors at the designed depths. The waling beams were also used to support the brickwalls, which formed the required backup wall for fixing the tiled water proofing system. Catch-drains were installed behind the brickwalls for relieving the ground water pressure and thus ensuring a very economic design. The adequacy of the system was proven in that where the system was not installed in time, failure of the sides occurred during monsoon. Whereas in the areas where the above retaining system was installed, there were no problems inspite of heavy monsoon and surcharge of construction materials and equipment. The system became a very effective and economic alternative to an anchored diaphragm wall. The paper presents the case studies of these two projects.

Jan 1, 1996

By Narong Thasnanipan

In Bangkok due to the prevailing condition of subsoil (existence of considerably weak stratum at top part) deep-seated large diameter bored piles of over 50 m depth with 0.8 -1.8m in diameter have been mainly used for heavy structures such as high rise buildings, elevated expressways, flyovers and more recently for underground subway stations of the first Bangkok MRTA system. As a part of pre-planned quality assurance regime and retrospective investigation, integrity of the piles are tested to obtain the information with regard to the potential deficiencies of the constructed piles which may have formed during pile construction process or may have been attributed by other activities after construction of the piles. An overview of three commonly used non-destructive tests such as sonic integrity, sonic logging and high strain dynamic load tests on deep-seated piles in Bangkok subsoil is presented in this paper. Advantages and limitations of each integrity test are discussed.

Jan 1, 2004

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 Koichi Kobayashi

Performance-based approach to design of structures including foundations was adopted after enforcement of the revised Building Standard Law in Japan in 2000. The use of piled-raft foundation is favorable for medium-rise buildings in soft ground because of its good performance. In the design of the piled-raft foundation (Architectural Institute of JAPAN2002), vertical load is usually carried by the raft foundation, while the pile is primarily meant to control settlement of the structure. Shaft friction is expected to be larger in a nodular pile(Karkee, et.al., 1998) since it has larger surface area than a straight pile, and such piles are frequently used in piled-raft foundations. Since few structures with piled-raft foundation exist currently, the settlement characteristics of piled-raft foundation have not been fully clarified. To design piled-raft foundations with better confidence, the mechanism of vertical bearing capacity and the spatial distribution of settlement should be clarified, for which the actual behavior of the building-foundation system needs to be evaluated. This paper presents observations of settlement of a building with a piled-raft foundation at a soft ground site. The building is a steel structure covering an area an 766 m2, and consists of two-storey office block and one-storey warehouse block. The filled ground of about 5-m thickness at the ground surface is underlain by approximately 4-m thick alluvial sand layer below which lies about a 17-m thick alluvial clay layer with SPT N-value less than 2. The piles used in the piled-raft foundation are 12-m long nodular piles with nodal diameter of 500 mm (pile shaft diameter is 400 mm). The bored pre-cast piling method (Karkee, et.al., 1998) was used to install the piles. To evaluate the foundation settlement, the method of analysis of three-dimensional frame system, utilized widely in Japan, was adopted in combination with the foundation system. Basic assumptions were: (i) total ground settlement is evaluated as the sum of immediate settlement and consolidation settlement, (ii) immediate settlement is evaluated from the Mindlin?s solution in which strain dependency of shear modulus of soil is considered, (iii) settlement in clayey layers is evaluated by the one-dimensional consolidation theory, and (iv) shear spring between soil and pile shaft is represented by a hyperbolic function. The applicability of the method of analysis was verified by comparison with results of field monitoring of building settlement.

Jan 1, 2006

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 Vahid Tajdar

The behavior similarity between pile and cone penetration test, has guided the researchers to use the CPT results in prediction of piles bearing capacity. In this article, artificial neural networks have been used to study about relation between cone tip and sleeve friction strength obtained from cone penetration test and ultimate pile bearing capacity, obtained from static pile load test. Artificial neural networks "ANNS" is a form of artificial intelligence. ANN tries to dramatize the human nerves & brain system biology structure in self-structure. In this article, the results of relevant studies about the prediction of ultimate pile bearing capacity in especial area of soils are presented by use of back - propagation neural networks. The results of static pile load test up to failure on 63 piles with closed end and CPT test results in the place of construction these piles use in order to confirm and creation ANN model. Comparing predicted ultimate pile bearing capacity by utilizing ANN with the numbers which are predicted by 5 common traditional methods shows that using of artificial neural networks is a suitable method for predicted ultimate pile bearing capacity in identified area of texture of soil moreover it has a better operation in comparison with common traditional methods.

Jan 1, 2006

By F. H. Chen

the Rocky Mountain Region since 1950, drilled pier foundations have been widely used to combat structural movement problems in expansive soils. It is now an accepted practice for engineers to use drilled pier foundations in expansive soil areas. Piers are generally drilled into bedrock in a zone unaffected by moisture change. With some exceptions, such system has successfully prevented damage incurred in the structures as the result of soil expansion. In the last 15 years, no significant advancement has taken place in the design of the drilled pier system on expansive soils. Numerous failures continued to be reported. Causes for the failures were placed on poor drainage, inadequate void under the grade beams or mushrooms on top of the piers. Engineers realize that these are certainly not the major problems. The basic design criteria should be critically reviewed. It is the purpose of this paper to point out the actual problems confronted by designers, the failure module and remedial measures, The writer does not claim to have the solutions. In fact, it will be a long time before real solutions can be found, yet the writer believes the engineering communities, the construction industry and the general public should be aware of the true picture of the problem.

Jan 1, 2010

By Zhu Tonghao

A method of calculating anti-slide pile, sheet pile, underground diaphragm and structure with anchors etc. is proposeed in the paper. The effect of the various layers of soil, anchors and bracings etc. on laterally loaded structures may be considered in the model. In the analysis the structure is divided into a series of elements. The transfer matrices of both deformation and internal force are established for each element. According to continuous condition neighbouring element should be connected. Thus the deformation and internal force of each element can be found out in conbination with boundary conditions. The method has a wider adaptability and it can be applicable to a great variety of the analysis of interaction between various structure and soil. If parameters in model are selected properly, the computed results would be in good agreement with the measured data.

Jan 1, 1991

By Fredrik Sarvell, Harald. Ihler, Veli-Matti Uotinen, Jukka Rantala

"Many of the valid international building codes state that the lateral support provided by the soil is sufficient to prevent buckling of fully embedded piles. However, the development of small diameter micropiles and especially the use of high strength steel have evolved to applications including high capacity elements. The ultimate structural load bearing capacity of a pile in a cohesive soil is decided by examining which gives the lowest value, the peak buckling load and the resisting moment provided by the surrounding soil medium or the structural capacity of the pile cross section. In both cases, the initial deflection of the pile is a significant factor when the axial load bearing capacity of the pile is determined. Steel micropiles are joined commonly with mechanical splices. A less rigid mechanical splice is often a weaker hinge that allows the pile to bend and deflect more during installation increasing the initial deflection of a pile. In addition the less rigid splice element decreases the bending capacity of a jointed pile section and the ultimate axial load capacity of the entire pile. A series of FE analysis performed for various pile sizes suggest that the steel pipe piles including separate pile sections and mechanical splicing elements should have the combined bending stiffness of EIshaft = 0,75 × EIpile. This requirement yields to the buckling resistance of at least 96 % of the solid reference pile with the sameinitial eccentricity in similar soil conditions.IntroductionMany of the valid international building codes state that the lateral support provided by the soil is sufficient to prevent buckling of fully embedded piles. However, the development of small diameter micropiles and especially the use of high strength steel have evolved to applications including high capacity elements. The potential buckling of these very slender high capacity piles in soft soils may in many cases be the controlling design factor of the pile, especially with end bearing micropiles.A typical sequence of soil strata in Nordic countries, such as Norway, Finland and Sweden, constitutes of friction soil or dry crust clay on top of soft clay followed by till. This soil stratum often rests on solid bedrock of granite or gneiss. Conditions like these are suitable for slender end bearing piles subjected to buckling and especially steel pipe piles where most of the material is located at the edge of the cross section. Other reasons for using slender steel pipe piles are for example fast installation with minimal waste, efficient manufacturing and relatively well established design and execution procedures. Minimum quality criteria’s regarding splices for steel pipe piles are recommended to be set as national provisions to ensure quality and comparable procurements in foundation business."

Jan 1, 2014

By W. D. Guo

With an experimental apparatus developed recently, model tests on piles were conducted in sand subjected to triangular soil movement profiles. Four instrumented piles tests are reported, which show the pile behavior predominantly determined by soil sliding depth. Axial load can create additional bending moment and pile deflection, which also make mode of pile-soil interaction change with sliding depth. Limiting resistance was found 1.5~3 times higher than currently used for laterally loaded piles in sand.

Jan 1, 2006

By Ke Yang

Drilled shafts are widely used as foundation system for sound walls to resist lateral loads. The design method based on the ultimate lateral capacity, such as Broms method, is often used for sound wall foundation design. Allowable Stress Design (ASD) is currently used for deep foundation design. However, by October 2007, all states Department of Transportations are required to use the Load Resistance Factor Design (LRFD) approach for the design of foundation in highway projects. There is a need to develop a calibrated resistance factor in LRFD lateral design of drilled shafts supporting sound barrier walls. This paper provides resistance factors for design of laterally loaded drilled shafts supporting sound walls using Broms method based on the study using reliability based method and fitting to ASD method. Additionally, the resistance factors for static lateral load tests are recommended. Furthermore, a methodology to update the resistance factors using Bayesian approach by incorporating the on-site full-scale lateral load test results is presented. To illustrate the Bayesian update methodology, two lateral load tests in Colorado were employed to develop the updated resistance factors.

Jan 1, 2007