考虑循环弱化效应的软土地基上半圆型防波堤稳定性分析

he semi-circular breakwater is a type of structure suitable for soft ground. Its foundation is subjected to not only long-term vertical loads, such as deadweight of the breakwater, but also the cyclic effects of horizontal, vertical and moment load components generated by the waves acting on the breakwater. There is no reasonable calculation method for evaluating foundation bearing capacity of the semi-circular breakwater on natural or reinforced soft foundation under combined loads. A quasi static finite element method for assessing cyclic foundation bearing capacity of the semi-circular breakwater on natural or reinforced soft foundation under combined loads is developed by combining the concept of cyclic shear strength of soft clay with D-P yield criterion. Then the proposed method is numerically implemented in the framework of the large universal finite element software ABAQUS. According to a practical project, the stability of the semi-circular breakwater is analyzed. The results show that foundation bearing capacity decreases obviously when considering cyclic weakening effect of soft foundation and foundation reinforcement has an obvious effect to increase foundation bearing capacity. Failure envelopes of structural bearing capacity under combined loads of horizontal force and vertical force are gained by adopting swipe load mode and load-displacement load mode, respectively. And three dimensional failure envelope surfaces of structural bearing capacity under combined loads of horizontal force, vertical force and moment are obtained by the method of combining load-displacement load mode with Swipe load mode. Furthermore, the effects of amount of filling sand in caisson, base bed width, and the reinforcement depth of foundation on stability of the semi-circular breakwater are analyzed. Compared with adding the base bed width, foundation reinforcement by driving plastic drainage plate is an effective way to improve foundation bearing capacity.