SOIL-PILE-STRUCTURE INTERACTION IN LIQUEFIABLE GROUND THROUGH MULTI-DIMENSIONAL SHAKING TABLE TESTS USING E-DEFENSE FACILITY

摘要

Geotechnical shaking table tests were conducted using the E-Defense facility to investigate the response and failure of a nearly full-scale pile-structure system in a liquefiable sand deposit subjected to multi-dimensional loading. A soil-pile-foundation system consisting of a foundation supported on a 3x3 steel pile group in a dry sand deposit was set in a cylindrical laminar box and then moved on to the shaking table for saturation of the ground, placement of a superstructure, if any, and the liquefaction tests. The sand deposit consisted of two layers including an underlying non-liquefiable dense sand layer and a liquefiable medium dense sand layer.Two types of ground motion having different predominant periods were used as input two-dimensional motions. The test results give detailed information on the distributions of bending strain and axial strain within the pile group as well as the ground response and pore water pressure generation in the soil around the piles. Not only the maximum acceleration but also the type of the input motion significantly affects the occurrence of soil liquefaction as well as soil-pile-structure interaction. All the pile heads yielded during the final test with high-level of input acceleration, causing residual deformation and settlement of the foundation.The pile damage was particularly significant on the leading side of the strong axis of the inertial force and ground displacement, suggesting that the difference in deformation mode of piles was affected by the difference in both axial strains and bending strains within the pile group.