Analysis Of The Stability Of The Breakwater On Soft Foundation Considering The Weakening Effect Under Cyclic Loading

In recent years, along with port scale expanding and utilization of the oceanspace, construction of offshore deepwater port is an important development directionof the waterway transportation business, while facing more severe conditions. Onone hand the sea environment is more complex, more severe wave conditions; on theother hand the foundation conditions for soft clay, bearing capacity decreases.Therefore, besides light structures which are more suitable for soft foundation areadopted in engineering, such as the large cylinder breakwater, semi-circularbreakwater, the softening effect of soft foundation produced in the repeated wavecyclic loading, which reduce the foundation bearing capacity and the stability ofstructures is an urgent problem. In view of above questions, combined with Tianjinsoft clay test, the paper carry out a series of research on the stability of structure onthe basis of dynamic weakening law of soft clay strength.The main contents are abstracted as follow:1. Use test data of Tianjin soft clay indoor dynamic-static test, combined themodel of pressure in soft clay hole and the reduction rule of shear strength withequivalent overconsolidation ratio formula,eventually get the dynamic variation ofsoft clay strength in different stress condition.This law shows the change of soft claystrength over time under wave cyclic loading.2. A3-D numerical model has been established with ABAQUS, write usersubroutine to make material parameters with the field variable change over time inthe ABAQUS platform. Then the above dynamic variation show on the twoindicators of soft clay, a finite element numerical model considering the softeningeffect has been established.3. Apply the finite element numerical model which consider the softening effectto get the stability of breakwater, in the quasi static and dynamic two methods,Compared with results of numerical model which ignore the softening effect toprove the harm of weakening effects about soft soil foundation, which should causeenough attention in practical engineering.4. Research on factors related to the safety and stability of breakwater structure especially from the structure depth and soil index. And take some conditions fromabove aspects for finite element analysis, finally suggest economic and effectivemeasures to improve structural stability.5. In the stability analysis, different instability criterion corresponding todifferent safety coefficient，in order to meet soil strength and structural requirements,this paper through the finite element analysis, provide reasonable suggestions forselection of instability criterion in foundation soil and put forward someimprovement in the current instability criterion.