The Behavior of Piles Driven in Clay. II. Investigation of the Bearing Capacity Using Total and Effective Strength Parameters

Abstract

This paper outlines research of large model piles and some full scale piles driven into insensitive clay to study the phenomenon of load transfer and the effect of pile driving on the soil. It is divided into two parts. Part I dealt with the stress field set up by driving a large model pile into an instrumented clay bed and the stresses measured for some full scale timber piles. Part II presents an evaluation of the load carrying capacity of the model pile and compares the results with full scale load tests. Soil properties are evaluated in terms of effective stress for an estimate of the bearing capacity of the piles.The short term bearing capacity of the pile shaft and base can be estimated by conventional methods based on the undrained shearing strength of the clay at the time of driving. However, after several load cycles and for long term bearing capacity, closer estimates are obtained by use of the effective skin friction and shearing strength parameters from drained tests. Previous bearing capacity theory can be used for estimating the ultimate base capacity and an approximate theory is presented to estimate the average effective radial stress on the pile shaft in connection with the ultimate shaft capacities. This proposed approach is supported by observations in some clays of low sensitivity, but requires further research in other types of clays.