Development Of ABAQUS Subroutine For Constitutive Model Of Triple-Shear Unified Elasto-Plasticity Bounding Surface Model For Saturated Sand

There is no uniform elastic-plastic boundary surface model of saturated sand tri-shear in ABAQUS finite element analysis software material library.In this paper,the model of saturated sand tri-shear uniform elastic-plastic boundary surface is compiled into ABAQUS subroutine on the platform of ABAQUS secondary development,and it is applied to the foundation pit excavation model.The main contents of this paper are as follows:(1)The common functions and basic components of ABAQUS finite element analysis software are briefly described,and the secondary development process and subroutine principle of ABAQUS subroutine are emphatically introduced;Based on the modified Cambridge model,the unified elastic-plastic boundary surface model of saturated sand with tri-shear force is introduced,and the failure stress ratio is modified so that the model can reflect the influence of the intermediate principal stress effect,stress interval effect,tensile pressure difference effect and soil cohesive force.It shows that the display integral algorithm of the adjoint error is easy to be applied to the complex constitutive model,and the accuracy of the display integral algorithm is greatly improved compared with the common display integral algorithm.The three-shear uniform elastic-plastic boundary surface model of saturated sand is compiled into UMAT subroutine using the display integral algorithm of adjoint error.(2)Take the sandy soil in nanchang area as the experimental sample,set the mass mud content of the sandy soil as 0%,5% and 10%,and conduct the conventional triaxial test of drainage and non-drainage under different confining pressures;Similar to the setting of soil in the conventional triaxial test,under different confining pressures and soil contents,single-variable undrained uniaxial cyclic load test was conducted under conditions of 0.5hz,1Hz and 2Hz,respectively.The simulation results of true triaxial monotone loading and unloading test with the UMAT subroutine compiled in this paper are compared with the numerical simulation results of true triaxial monotone loading and unloading test to verify the correctness of the subroutine numerical implementation.In this paper,the UMAT subroutine isused to simulate the conventional triaxial test of saturated sand soil.(3)The last on the ABAQUS to set up a three layer model of the excavation of foundation pit,in the UMAT subroutine to b separately 0,1,0.25,0.5,0.75,and it is found that with increasing b foundation settlement,vertical displacement and horizontal displacement of soil,and even the wall of the lateral became smaller,indicating that the soil shear strength in constant increase,more able to exert the strength of the soil mass,the finite element analysis results are consistent with the theory...