INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS. VOL. 9, zyx 507-524 (1985). DYNAMIC ANALYSIS OF PILES AND PILE GROUPS EMBEDDED IN NON-HOMOGENEOUS SOILS zy R. SEN* zyxwvut University of South Florida. Tampa, FL 33620, U.S.A. E. KAUSEL' Massachusetts Institute of Technology. Cambridge, Mass 021 38, U.S.A. AND P. K. BANERJEE' State University of New York. Buflalo. N.Y. zyxwv 14260. zyxwv U.S.A. SUMMARY A hybrid boundary element formulation for the steady state analysis of piles and pile groups embedded in a soil stratum in which the modulus increases linearly with depth is presented. The piles are represented by compressible columns or flexible beams and the soil as a hysteretic, layered medium. The explicit Green's function corresponding to dynamic loads in the interior of a layered stratum, developed earlier by Kausel is used in the study. The governing differential equations for the pile domain are solved for a distributed periodic loading intensity and those for the soil domain by a system of boundary elements at the pile-soil interface.These are then assembled into a system of algebraic equatians by satisfying interface equilibrium and compatibility. The results of the analysis have been compared against those from alternative formulations, e.g. finite elements, and confirm the accuracy of the proposed formulation. Representative results for single piles and pile groups are presented. INTRODUCTION The response of piles and pile groups to dynamic excitation has been the subject of much investigation over the past decade. A review' of the research undertaken to date indicates that although some outstanding efforts exist in the published the scopes of some of the solution procedures developed are restrictive and cannot always be extended to the generalized analysis of pile groups subjected to axial and lateral loading. The underlying problem in analysing pile groups is, of course, in the representation of the soil surrounding the piie and that of the far field, i.e. boundaries at infinity. The simplest model used represents the soil as a Winkler foundation with distributed springs and dashpots that are constant or frequency dependent, or lumped springs concentrated at a finite number of nodes. The spring constants are obtained from analytical considerations or from experimental data. The major advantage of this approach lies in its ability to simulate non-linearity, inhomogeneity and *Assistant Professor :Associate Professor 'Professor zyxwvutsr 0363-9O61/85/060507- 18%01.80 zyxwvu 0 1985 by John Wiley zyxwvuts & Sons, Ltd. Received 20 February 1984 Revised zyxw I2 October 1984