剛塑性有限要素法を用いた二層系粘性土地盤の直接基礎の支持力解析

Abstract

The ultimate bearing capacity formulas of foundation and penetration foundation have been specified in the guideline published by Architectural Institute of Japan for design of building foundation. The rigid plastic finite element method was developed by Tamura and Ohtsuka and has been applied to estimate the ultimate bearing capacity of footing. The characteristic of this method is to employ limited soil constants in comparison with deformation analysis. It only uses the strength parameters as cohesion, c and friction angle, φ since it deals with the limit state directly by disregarding the deformation of building and ground. Through a series of rigid plastic finite element analyses, the comparison of ultimate bearing capacities of penetration foundation between the simulation results and the formula of Architectural Institute of Japan was conducted for two layered soil system of clay. The change in failure mode of ground was discussed with the geometrical ratio between the width of footing and the height of surface layer. The strength ratio of the surface and the second layers of ground was clearly shown to affect the formation of failure mode. The applicability of rigid plastic FEM was demonstrated to the assessment of ultimate bearing capacity of two layered clayey soil system.