Three-dimensional non-coaxial constitutive model for sand and its application in bearing capacity of foundation

Due to the coaxial assumption that the direction of plastic strain rate is the same as that of stress, the non-coaxial behavior of sand under non-proportional loading conditions can not be captured by the conventional elastic-plastic model. In this study, firstly the cause of coaxial hypothesis contained in the traditional model is analyzed. Then, a non-coaxial model for sand is constructed by introducing the generalized non-coaxial plastic flow theory developed by Hashiguchi et al into the state-dependent dilatancy model for sand established by Li et al. The simulation of simple shear tests on Leighton-Buzzard sand shows that the non-coaxial model can describe the experimental results more reasonably. The corresponding finite element program is developed, the bearing capacity of sand foundation under different void ratios is analyzed by using the proposed model. The influence of non-coaxial parameters on the calculation results is discussed, and the predicted results demonstrate similar characteristics with those of simple shear test simulation on the whole.