Scientific approaches to pile design have advanced enormously in recent decades and yet, still, the most fundamental aspect of pile design—that of estimating the axial capacity—relies heavily upon empirical correlations. Improvements have been made in identifying the processes that occur within the critical zone of soil immediately surrounding the pile, but quantification of the changes in stress and fabric is not straightforward. This paper addresses the degree of confidence we can now place (a) on the conceptual and analytical frameworks for estimating pile capacity, and (b) on the quantitative parameters required to achieve a design. The discussion is restricted to driven piles in clays and siliceous sands, with particular attention given to extrapolating from design approaches derived for closed-ended piles of relatively small diameter to the large-diameter open-ended piles that are used routinely in the offshore industry. From a practical viewpoint, we need design approaches that minimise sensitivity...

Science and empiricism in pile foundation design

Local impact effects of hard missiles on concrete targets

Over the last few years or so, the use of artificial neural networks ( ANNs) has increased in many areas of engineering. In particular, ANNs have been applied to many geotechnical engineering problems and have demonstrated some degree of success. A review of the literature reveals that ANNs have been used successfully in pile capacity prediction, modelling soil behaviour, site characterisation, earth retaining structures, settlement of structures, slope stability, design of tunnels and underground openings, liquefaction, soil permeability and hydraulic conductivity, soil compaction, soil swelling and classification of soils. The objective of this paper is to provide a general view of some ANN applications for solving some types of geotechnical engineering problems. It is not intended to describe the ANNs modelling issues in geotechnical engineering. The paper also does not intend to cover every single application or scientific paper that found in the literature. For brevity, some works are selected to be described in some detail, while others are acknowledged for reference purposes. The paper then discusses the strengths and limitations of ANNs compared with the other modelling approaches. The engineering properties of soil and rock exhibit varied and uncertain behaviour due to the complex and imprecise physical processes associated with the formation of these materials (Jaksa 1995). This is in contrast to most other civil engineering materials, such as steel, concrete and timber, which exhibit far greater homogeneity and isotropy. In order to cope with the complexity of geotechnical behaviour, and the spatial variability of these materials, traditional forms of engineering design models are justifiably simplified. An alternative approach, which has been shown to have some degree of success, is based on the data alone to determine the structure and parameters of the model . The technique is known as artificial neural networks ( ANNs) and is well suited to model complex problems where the relationship between the model variables is unknown (Hubick 1992). This paper is intended to be for readers in the field of geotechnical engineering who are not familiar with artificial neural networks. The paper aims to detail some features associated with ANNs through a review for some of their applications to-date in geotechnical engineering. It is hoped that this review may attract more geotechnical engineers to pay better attention to this promising tool. The paper starts with a brief overview of the structure and operation of the ANNs and gives a general overview of most ANN applications that have appeared in the geotechncial engineering literature. Finally, the paper discusses the relative success of ANNs in predicting various geotechnical engineering properties and behaviour.

Artificial neural network applications in geotechnical engineering

This report contains the findings of a study to develop resistance factors for driven pile and drilled shaft foundations These factors are recommended for inclusion in Section 10 of the AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications to reflect current best practice in geotechnical design and construction The report also provides a detailed procedure for calibrating deep foundation resistance The material in this report will be of immediate interest to bridge engineers and geotechnical engineers involved in the design of pile and drilled shaft foundations

Load and resistance factor design (lrfd) for deep foundations

Prediction of pile bearing capacity using a hybrid genetic algorithm-based ANN

An analytical method for developing a theoretical load-settlement curve for axially loaded piles in clay is presented. The method is based on the correlation of the ratio of load transfer to soil shear strength as a function of pile movement. The results of studies of field tests of instrumented piles and laboratory tests of small piles in clay are used to obtain the desired correlation. The correlation is presented in the form of a family of curves that are obtained when the ratios of load transfer to soil shear strength versus pile movement are plotted as a function of depth. The validity of the family of correlation curves is checked by comparing computed and actual load-settlement curves for some typical field tests. Results obtained by this method indicate that the method may be used effectively to determine load-carrying capacity for axially loaded piles in clay.

Closure to “Load Transfer for Axially Loaded Piles in Clay”

Load Transfer for Axially Loaded Piles in Clay

A critical review of the literature clearly shows that existing theories which are used to determine the bearing capacity of piles driven in sand are not satisfactory Careful examination of the results of experimental studies indicates that existing theories fail to consider all significant parameters Field load test data are used to determine which of the pile geometry and soil property parameters are significant Special attention is given to the problem of residual stresses Bearing capacity factors are calculated from measured unit point and side resistances The bearing capacity factors are correlated with relative depth (depth of penetration to diameter ratio) and friction angle or relative density of sand New design correlations are developed for use in predicting the bearing capacity of axially loaded piles in sand

New Design Correlations for Piles in Sand

A relationship is presented between skin friction and soil shear strength as a function of pile movement for steel piles in sand. Consideration is given to the effect of void ratio, saturation, depth or lateral pressure, and movement. The results of a study of a field test on instrumented piles and laboratory tests on a small pile in saturated sand are used to obtain the desired relationship. The relationship is presented in the form of a curve which is obtained when the ratio of skin friction to soil shear strength is plotted versus pile movement. The developed curve is used to compute a theoretical load-settlement curve which, in turn, is compared with an actual field load-settlement curve.

Skin Friction for Steel Piles in Sand

The results of a laboratory investigation of the damping properties of saturated sands and clays of relatively high plasticity are reported. An effort is made to relate these damping properties to common physical properties of the soils tested. A series of dynamic (impact) and static tests were performed on a variety of sand and clay soils. The sands varied in grain size and grain shape, and the clays varied in plasticity and moisture content. Velocity of sample deformation, peak dynamic loads, and peak static loads were measured so that damping constants for the soils could be evaluated. A mathematical model in current use which describes soil action at the point of a pile is examined. The model is used in wave equation studies of piling behavior. A modification of this model is made in order to achieve a constant damping value over the full range of loading velocities. Damping constants are evaluated for all soils tested. The damping constant is related to void ratio and effective angle of internal shearing resistance in sands, and moisture content and liquidity index in clays.

Harry M. Coyle

Papers

Closure to “Load Transfer for Axially Loaded Piles in Clay”

Load Transfer for Axially Loaded Piles in Clay

New Design Correlations for Piles in Sand

Skin Friction for Steel Piles in Sand

Empirical Damping Constants for Sands and Clays