Experimental Study And Numerical Simulation On Dynamic Characristics Of Soft Clay Under High Dynamic Stress Level

In recent years,China's port construction has developed rapidly.With the engineering becoming deeper and larger,the bearing capability of soft clay foundation must meet higher requirements.The research shows that the dynamic characteristics of the soil are different when subjected to dynamic load of different stress level.The soil will undergo cyclic failure under the action of high dynamic stress load,and the soil will exhibit cyclic stability under the action of low dynamic stress load.The critical value of the high and low dynamic stress level is called critical dynamic stress.A lot of research work has been carried out on the weakening of soil strength under the action of low dynamic stress load;the cyclical failure of soil strength under high dynamic stress load is a problem to be further studied.In this paper,a series of dynamic triaxial tests were carried out on Yantai remolded saturated soft clay.The numerical simulation was carried out by using finite element analysis software.The dynamic deformation and dynamic pore pressure of remolded saturated soft clay under high dynamic stress level were systematically studied.The dynamic strength development law was established,and the dynamic strength variation model considering the cycle number,confining pressure,drainage static deviator stress and overconsolidation ratio was established and applied to the finite element analysis calculation.Through the model calculation,the distribution law of the failure zone of the soil under cyclic loading and the influence of the cyclic failure of the foundation soil on the bearing capacity of the whole foundation are explored.The main contents are abstracted as follows:(1)Carry out a series of dynamic triaxial tests on saturated soft clay.The dynamic deformation,dynamic pore pressure and dynamic elastic modulus subjected to different cyclic dynamic stresses,cycle times,consolidation confining pressure,drainage static deviator stress and over-consolidation ratio under high dynamic stress level has been analyzed.The variation law of critical dynamic stress of soil under different consolidated pressure conditions is explored,and the formula of critical dynamic stress with consolidated pressure is obtained.(2)Fitting the dynamic test data of soil,and obtaining the dynamic strength variation model considering confining pressure,drainage static deviator stress,overconsolidation ratio and cycle number,summing up the dynamic strength with different confining pressure and drainage static deviatoric stress,the degree of over consolidation and the number of cycles.The variation law of dynamic strength under different failure criteria was studied,and the difference of soil dynamic strength between different failure criteria was analyzed.The critical dynamic stress obtained from the test is compared with the calculated dynamic strength of the dynamic strength model.(3)Through the secondary development of ABAQUS,the dynamic strength variation model is combined with the strength weakening model,and the finite element calculation is used to carry out more accurate numerical simulation of the variation law of soil unit strength subjected to different dynamic stress amplitude ranges.The finite element dynamic calculation model is improved,and the strip foundation finite element model is used to calculate and analyze the ultimate bearing capacity of foundation under different working conditions.(4)Based on the actual breakwater engineering,the numerical model is established to further explore the distribution law of soil failure zone and the change law of soil strength by factors such as horizontal wave force,vertical wave force,caisson sand filling amount and thickness of replacement sand layer.The impact and further explore the changes of foundation bearing capacity under the influence of different factors,and provide reference for practical engineering.