Research And Applicatiton Of Cyclic Viscoelastic-Plastic Constitutivemodel Of Soft Clay Under Cyclic Loading

With the rapid development of the economy,more andmore transportation facilities are built on soft clay foundation.During the operation of transportation facilities,the plastic cumulative deformation of soft clay foundation,which will influence the normal operation and even safety of vehicles,will be gradually increased under traffic load.Aiming at the quesion,considering the influence of soil structure degradation and based on the nonlinearmotion hardening rule and visco-elastoplastic theory,a cyclic visco-elasto-plastic constitutivemodel suitable for dynamic analysis of soft clay is established in this paper.With the aid of the secondary development platform of the ABAQUS software's UMAT subprogram interface,the numerical calculation of the dynamic characteristics of soft clay under cyclic loading is carried out.It will be very helpful for the settlement calculation of complex practical engineering on the soft clay foundation under dynamic loading.Themain research contents and conclusions of this paper are as the following:(1)Firstly,based on nonlinearmotion hardening rules and visco-elasto-plastic theory and considering the influence of soft clay structure degradation,a cyclic visco-elastoplastic constitutivemodel of soft clay was built in this paper,A usermaterial subroutine was also established for the dynamic response analysis of soft clay under cyclic loading by using the secondary development platform of the finite element software ABAQUS.The finite element simulations of laboratory dynamic triaxial tests on stress control and strain control were performed by callying the usermaterial subroutine of cyclic visco-elastoplastic constitutivemodel.The plastic accumulation of soft clay under different confining pressures,stress ratios,and loading frequencies were studied.Strains,stress-strain relationships,and the evolution of effective paths were compared with the experimental results.The results show that the cyclic visco-elastoplastic constitutivemodel can simulate the plastic cumulative deformation of soft clay,the stress-strain relationship and effective stress path under cyclic loading.(2)Secondly,a large number of finite element simulation analyses were performed on the stress-controlled indoor dynamic triaxial test by controlling the different values of themodel parameters.The simulation results and test results of each parameter under different values were compared and analyzed.The plasticity parameter had a great influence on the shape of the calculation result.It also controlled the convergence trend of the cyclic plasticity cumulative strain-cycle number relationship curve.The hardening parameter and scalar hardening parameter had almost the same effect with the plasticity parameter,and the cumulative plastic strain increased with the parameter value.(3)Finally,the cyclic visco-elastoplastic constitutivemodel was used to simulate the long-term settlement or deformation of Saga Airport Highway under traffic loads.The settlement or deformation law of the soft clay ground under the traffic load calculated by themodel in this paper was obtained.A comparative analysis between the prediction results of the empirical formula and the actualmeasurement results shows that the prediction results of themodel in this paper fit better with the actualmeasurement results.When the driving load is greater than the critical value,the settlement or deformation of soft clay foundation increased linearly.The results show that the cyclic visco-elastoplastic constitutivemodel can effectively predict or calculate the settlement or deformation of soft clay foundation under traffic load.