Study On Active Earth Pressure Based On Limit Analysis Method

The topic of earth pressure is one of the three classical topics of Soil Mechanics. Coulomb’s theory and Rankine’s theory are based on several given conditions, and the active earth pressure is consumed to satisfy a linear distribution which doesn’t match with the measured value. For the existence of some defects in the traditional theories, the active earth pressure is analyzed in the thesis based on the limit analysis method. Specific work as following:(1) Translational failure mode and rotary failure mode are assumed to be the failure modes of soil. Plane is the failure surface under translational failure mode while logarithmic spiral surface under rotary failure mode based on the limit analysis method.(2) Divided into two cases of homogeneous soil and two layers of soil, active earth pressure formulas, which meet the associated flow rule, are given under translational failure mode. And the impact form of various parameters is detailed analyzed. After comparative analysis, we know that the calculated results of homogeneous soil based on the limit analysis method is the same as the criteria’s, and the calculated results of two layers of soil is a little smaller than traditional method’s due to without taking into account the boundary conditions of the walls, the cohesion as well as the nonlinear distribution of active earth pressure in traditional method.(3) Active earth pressure formulas which tell us the relationship among active earth pressure, point of application of earth pressure and the rotation center are given under rotary failure mode. With the curvature of the failure surface increasing, the active earth pressure is greater and the application point of earth pressure is higher. Based on the formulas under rotation failure mode, methods to solve the situation of translational failure mode (T mode) and rotation around the top of the wall (RT mode) are deduced. The calculated results by the formulas under rotary failure mode while the center of rotation is infinitely distant, is the same as the one under translational failure mode.(4) Finally, the impact form of various parameters is detailed analyzed. And the application point of earth pressure is found to be in roughly0.2to0.4times the height of the wall under the situation of translational failure mode (T mode) while roughly0.5to0.7times the height of the wall under the situation of rotation around the top of the wall (RT mode). So the active earth pressure is nonlinear distributing under translational and rotation failure mode.