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By Bernard H. Hertlein

The introduction of LRFD methods for structural design has been a gradual process by AASHTO, ACI, AISC, ASCE, and the FHWA, which has largely been ignored by the deep foundations industry. In 2007, however, the industry has been obliged to embrace LRFD for any deep foundations on projects involving federal funds. The authors are concerned that the risks caused by the need for, and the difficulty of providing, reliable quality assurance, will result in unnecessarily high safety factors that will defeat part of the purpose of LRFD. A primary attraction of LRFD for owners and engineers alike is that it promises more efficient design, and therefore cost reductions. Unfortunately, a key element of LRFD philosophy is often overlooked - that the applied safety factors can be rationally reduced, often allowing less material to be used, thus saving costs, but only if all the risk factors involved are identified and closely controlled. This means that both the quality of the materials and the quality of the construction work must be adequately monitored, and held to an acceptable standard. In the case of deep foundations, the soil in which the foundation is constructed is also a critical component that must be taken into account in the assessment of risk factors.

Jan 1, 2007

By Helen Ahnberg

The scope of the present paper is limited to report the experimental evidence and not for describing the analytical assumptions. However, the idea behind the experimental program is that the deterioration may be caused by the leaching of Ca from the treated soil to surrounding soil or water driven by the difference in the Ca ion concentration. As a consequence of Ca leaching, it may be natural to expect the expansion of micro void space within the treated soil. In a saturated condition, the water inflow into the treated soil may accompany the leaching phenomenon. We measured the water content within the treated soil. But there is not much difference in water content within the soil.

Feb 10, 2003

By V. T. Ganpule

The effect of Sulphate and Chloride is well understood by the engineers. Most of the codes stipulate permissible limits for sulphate and chloride content in groundwater. Relatively few reference are available about the effect of organic acids on pile concrete. While executing a pile foundation work around Bombay, the authors came across the peculiar phenomenon. The routine testing of water has indicated that water is non-aggressive; however, on exposing the piles, the piles were found to be highly detonated. The testing of water on the guidelines followed by engineers associated with flow through pipes revealed that water is corrosive as per the Ryznar index concept. The present papers discussess the significance of Ryznar index in under water concreting.

Jan 1, 1996

By Wang Huichang

A tentative mathod for predicting load-settlement relationship and bearing capacity of single piles based directly on the results measured by cone penetrometer with local friction sleeve is presented. It is possible that the load-settlement curves can be constructed by means of CPT and the problem of both the bearing capacity and the settlement behaviour of single piles can be considered jointly. The proposed load-transfer functions are continuous, positive monotonic and nonlinear. a concept of weight mean point resistance 2D above and 4D underneath the pile base to determine the unit ultimate base resistance of piles is presented. The predicted results of seven jacked piles in loess are in good agreement with the load test data.

Jan 1, 1991

By Shamsher Prakash

Estimation of vertical load carrying capacity of a single vertical pile under earthquake loading is an important task of a design engineer. Lateral vibration of vertical pile is highly influenced by the magnitude of vertical load. Several load reversal, during earthquake loading introduce gap between pile soil interface which reduces its load carrying capacity and increases lateral motion. This paper presents a simple time domain numerical scheme to estimate the lateral pile response, considering the loss of contact of pile at pile soil interface, during impact and earthquake loading. The motion of the pile is limited in the vertical plane. Time domain has been discretised into small intervals. The non linearity of soil properties has been taken into account by discretised Winklers model with Wolfes frequency independent mass spring dash pot coefficient for geometric damping. Suitable software has been developed which keeps track of the load reversal point of each elements.

Jan 1, 1996

By Kenneth M. Berrry

A unique situation has developed at an abandoned coal mine in St. Clair County, Illinois. Subsidence features have been observed at the ground surface over the mine including settlement of a pair of bridges for Illinois Route 158. The Illinois Department of Transportation (IDOT) is currently replacing the two bridges. Foundation treatment for the two new bridges included backfilling the mine void. The light rail system for St Louis (MetroLink) is also constructing a bridge over the same abandoned coal mine less than 1000 ft from the Route 158 bridges. The new MetroLink bridge is being constructed using piles which extend through the coal mine and overlying bedrock in order to transfer the loads to below the mine floor. The differing foundation types for the IDOT and MetroLink bridges were due to geometry and economic factors involved with the individual structures.

Jan 1, 2001

By Madhira R. Madhav

In an alluvial deposit consisting of layers of sandy silt with clay and kankar nodules, driven cast in situ piles are provided. The piles end on a stiff bearing stratum To verify the available design capacities, compression, pull-out and lateral load tests are conducted in situ. The elastic continuum approach is used to estimate the equivalent modulus of deformation of the deposit. A comparison is made of the values from the three types of tests.

Jan 1, 1996

By A. Ghorbani

The analysis of Combined Pile Raft Foundation (CPRF) is very complex due to involved interactions among components of CPRF system. Many researchers made efforts to develop sufficient methods including three dimensional finite element methods to compute these interactions. Since there are some restrictions and complexity in previous methods, in present study a new approach based on three dimensional finite difference methods is implemented to overcome some of these restrictions. The total and differential settlements of a centrifuge case study are computed using different numerical methods to show the performance of present numerical approach.

Jan 1, 2007

By K. C. Foye

Use of load and resistance factor design (LRFD) of foundations is growing, from offshore applications to bridge applications and beyond. The development of load and resistance factors for design has traditionally relied on calibration to traditional factors of safety. This technique, however, offers little insight into the challenges of pile design. This paper discusses an approach to LRFD factor development that seeks to isolate the various sources of design uncertainty. Using this approach, reliability analysis is used to develop resistance factors for the design of driven pipe piles in sand. These findings shed light on many aspects of the ongoing discussion of how LRFD can be successfully applied to pile design.

Jan 1, 2008

By S. L. Karunakaran

There are cases where it is found that a raft foundation would have adequate factor of safety against ultimate bearing capacity failure but the settlements would be excessive. Piles may be introduced in order to limit settlements to an acceptable level. The actual number of piles required to reduce the settlements to an acceptable level may be very small compared to the number of piles required to transmit the whole structure load. The paper focuses on the difficulties encountered in evaluating the load sharing between raft and piles. An elaborate analysis taking into account the interaction between raft, piles and soil is very complex and time consuming. Few approximate methods for arriving at a satisfactory solution to piled raft system are discussed in the present paper.

Jan 1, 1996

By Y. W. Mou

In order to improve the construction of pile foundations and deep foundations of largo sizes, the paper deals with the method of installing square or rectangular bored-piles for annular foundation as well as large-sized hollow or solid foundation.

Jan 1, 2010

By Sun Gengsheng

Geotechnical properties of soils, usual types of pile foundations, pile capacity, calculation of settlements of pile foundations, usual types of retaining structures for deep excavation, stability analysis of retaining structures and Anti-buoyancy soil anchors in Shanghai.

Jan 1, 1991

By Jonathan Ernst

The Bruce Museum is an art, science and natural history museum in Green- wich, Connecticut. The museum was originally built as a private residence in 1853, and has undergone several reno- vations, the most recent dating to 1992. The current renovation is part of a $60 million capital expansion plan for the "New Bruce." The renovation includes a 43,000 sf (4,000 m2), three-story addition that will more than double the size of the museum, adding space for new ex- hibitions, education and community spaces. The proposed bottom of the foundations for the renovation sit up to 16 ft (5 m) below the Bruce Museum's existing shallow foundations.

Aug 1, 2023

By Richard Schmidt, Lijun Deng, Mohamed Abdelaziz, Weidong Li

Helical piles are widely used as a foundation supporting a variety of different structures. Understanding the axial behaviour of helical piles is required to confirm the engineering design. Helical pile research is often conducted in the field, but this method can be prohibitively expensive in some cases. Geotechnical centrifuge modeling offers an alternative method for the helical pile research and practice. A series of axial load tests of helical piles installed into cohesive soils were conducted on the geotechnical centrifuge at the University of Alberta. The objective was to investigate the effects of inter-helix spacing and soil strength on the axial behaviour of helical piles. Four types of aluminum model helical piles including one single-helix pile and three double-helix piles with various inter-helix spacing ratios were tested. Both compressive and tensile loading tests were conducted. All model piles were instrumented with multiple strain gauge stations. The clay had an undrained shear strength of approximately 50 kPa and 120 kPa. The test results indicate that there is a transitional failure mode between the two widely recognized failure modes, i.e., individual plate bearing and cylindrical shearing. The shaft adhesion was significantly reduced by the helix. Axial capacities were comparable to the field test results.

By RAP Bement

Installation by vibrodrivers of sheet and bearing piles generates periodic vibrations in the surrounding ground, which have been widely measured and reported. One of the possible consequential effects of these vibrations is ground settlement caused by the compaction of loose granular soils. Vibratory compaction settlement of a range of granular soils has been studied in the laboratory using a 150mm diameter Rowe cell, which allows sample preparation and control during vibrations equivalent to conditions in the field during vibrodriving. The cell containing the soil sample was mounted on an electromagnetic shaker and vibrated at amplitudes and frequencies appropriate for soils adjacent to vibrodrivers. The changes in sample height were recorded.

Jan 1, 1996

By Lin Li

A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. In the past effort, a deterministic method using the limiting equilibrium method of slices for determining the global factor of safety of a slope reinforced by a row of drilled shafts was developed using the soil arching concept. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which reduces the driving forces on the down slope side of the drilled shaft. The effect of drilled shafts induced soil arching on the reduction of the driving stresses in the limiting equilibrium slope stability analysis was quantified by the load transfer factor through extensive finite element simulation studies. A semi-empirical equation was also developed for expressing the load transfer factor as a function of the soil properties, including strength parameters and unit weight as well as the slope geometry and soil profile, the location and spacing of the drilled shaft, and the dimension of the drilled shaft. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, a modification of the deterministic method into a probabilistic method is developed in this paper. The Monte Carlo statistical method is used to generate random variables for the soil strength parameters based on the prescribed probability characteristics, including mean, COV, and the probability distribution function. In addition, the modeling error of the load transfer factor is also treated as a random variable in the Monte Carlo simulation method, in which the mean, COV, and probability distribution function for the bias of the semi-empirical equation are used. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Two examples are shown in the paper to illustrate the analysis results of the developed probability approach for determining the reliability of a drilled shaft stabilized slope system.

Jan 1, 2017

By Lin Li

A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. In the past effort, a deterministic method using the limiting equilibrium method of slices for determining the global factor of safety of a slope reinforced by a row of drilled shafts was developed using the soil arching concept. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which reduces the driving forces on the down slope side of the drilled shaft. The effect of drilled shafts induced soil arching on the reduction of the driving stresses in the limiting equilibrium slope stability analysis was quantified by the load transfer factor through extensive finite element simulation studies. A semi-empirical equation was also developed for expressing the load transfer factor as a function of the soil properties, including strength parameters and unit weight as well as the slope geometry and soil profile, the location and spacing of the drilled shaft, and the dimension of the drilled shaft. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, a modification of the deterministic method into a probabilistic method is developed in this paper. The Monte Carlo statistical method is used to generate random variables for the soil strength parameters based on the prescribed probability characteristics, including mean, COV, and the probability distribution function. In addition, the modeling error of the load transfer factor is also treated as a random variable in the Monte Carlo simulation method, in which the mean, COV, and probability distribution function for the bias of the semi-empirical equation are used. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Two examples are shown in the paper to illustrate the analysis results of the developed probability approach for determining the reliability of a drilled shaft stabilized slope system.

By Bastian Hoffmann, Christian Moormann

The paper presents results of an experimental study on the axial load bearing behavior of vibratory driven full displacement piles in comparison with impact driven and cyclic quasi-static installed piles in dense sand. The test setup and the measurement devices used to this end are explained. Subsequently, the results of the axial loading like load settlement curves are shown and the impact of the installation method is interpreted. The results presented in this work are mainly based on three installation methods: test series one investigates axial behavior of vibratory driven piles, test series two describe the same cyclic pile installation process but without dynamic influence wherein a special test setup developed to install the piles cyclic quasi-static in the soil was used. A third test series carried out using the conventional impact pile driving method served the purpose of not only comparing the results against vibratory driving, but also aided in isolating the effects of dynamics inherent to the vibratory driving process.

May 1, 2022

By Mario Carnevale, Myles Danforth, Michael Oakland

The cost and overall effectiveness of foundation design depends on a robust characterization of the subsurface geologic setting. It is common practice to formulate deep foundation design from subsurface geologic characterization based on boring programs. The confidence level of geologic characterization is directly related to that of geologic interpretations, which are based on the spatial sampling pattern of boreholes relative to the complexity of the geologic setting. This paper presents a case history illustrating issues that arise during pile construction from over-simplified geologic characterization, the challenging steps taken to improve the subsurface geologic model, and the effect of additional characterization efforts on the pile foundation program. The seismic characterization methods used include multi-channel analysis of surface waves (MASW) and seismic refraction.

By Wang Mingshu

The pile foundation is a kind of advanced foundations in the filled or soft soil. In this paper, through the actural engineering of coal dressing plant of Western Opencast Coal in Fushun built on the mining dump with large diameter pile foundation, the construction method and mechanics analysis of pile are given. Unless it is in following stadge, the stability of pile cannot be lost due to its small rigidity. The analysis shows that pile foundations of large diameter ellipse section can decreased hotizontal displacement to 60% ?70% of that of equal section an in the design of a single pile and a single column, the ellipse pile and manual dig hole are most favourable. So a large amount of concrete can be saved.

Jan 1, 1991