PILE-SOIL INTERACTION IN LIQUEFIABLE SOILS

Abstract

Studies of seismic loading of substructure (e.g. piles) and liquefaction phenomenon are more than four decades old; however the combined problem of seismic behaviour of piles in liquefiable soil has received less attention. Most of the several experimental and analytical studies of this combined problem have been presented only in the last decade. Yet much has to be revealed especially the influence of flow characteristic on the behaviour of the system. Therefore, a study on the performance of piles in liquefiable ground under earthquake loading is considered here. The numerical formulation of modeling of liquefaction and pile-soil interaction are described. The available models that formulate the pore pressure response directly from observed data on undrained tests have been used to study the liquefaction phenomenon, while Winkler model has been used to study the pile-soil interaction. Finally combining these two models, a formulation to predict the response of pile in liquefiable soils has been developed. A computer code in C++ has been developed on the basis of this formulation and the response of pile in liquefiable soils for both axial and lateral load in the time domain has been predicted. The results of the study show that the axial displacements are prominent for the frequency equal to the natural frequency of the soil. Also it has been observed that the effect of liquefaction is not significant at lower frequency for axial load. But it has been observed that the interacting forces are drastically reduced at all frequencies because of the reduction in shear modulus due to liquefaction. For lateral load the displacements and bending moments have been increased significantly due to liquefaction.