Settlement analysis of pile groups in layered soils

Abstract

This paper presents a method to perform a nonlinear analysis of pile groups subject to vertical loading. The method makes use of the dynamic stiffness matrices to simulate the response of layered soils. These matrices are incorporated in a calculation procedure that is computationally very efficient because the response of a pile group can be achieved using essentially the solution for a single pile. The method is first used to perform a linear elastic analysis of pile groups and is then extended to include the nonlinearity effects. In this context, the widely accepted approach is adopted in which nonlinearity is considered to be confined in a narrow zone close to each pile, whereas outside this zone the soil is assumed to behave as a linear elastic medium. Moreover, a global interaction factor is introduced to account for the interaction among the piles in the group. The theoretical predictions from the proposed method are compared with experimental measurements from several published full-scale and model tests on pile groups loaded up to failure. The agreement between predicted and observed behaviour is found to be very satisfactory, even approaching the ultimate load, when the results of loading tests on single piles are available and the group efficiency with respect to the failure load is close to unity.Key words: pile groups, settlement analysis, nonlinear behaviour, layered soils.