Research On The Triple-Shear Unified Dilatancy Constitutive Model For Sand And The Secondary Development For ABAQUS

Dilatancy isone of the most basic and important properties of sandy soils.The research on the constitutive model of sand will be more meaningful.The mainly content of this paper can combinate the triple-shear unified strength theory with the dilatancy. Based on the modified Cam-Clay model, the dilatancy of middle dense sand soils is considered to modify the Cam-Clay model. The peak value of stress ratio, yield equation and hardening parameter is modified according to the triple-shear unified strength theory. Based on the mechanics principle, the elasto-plastic stiffness matrix of the new model can be derived from the triple-shear unified strength theory and the new constitutive model which contains the properties of sand.Based on the sand in Nanchang, under the tests of conventional tri-axial test,The results not only can show the properties of sand soils in nanchang, but also can verify the validity of the constitutive model.The finite element subrourine of the triple-shear unified dilatancy model is composed by Fortran on the second development platform.The curves of stress-strain are simulated in different drainage condition under the tests of conventional tri-axial test. The simulation is compared with the experimental data, it can shows that the model is convincible.The use of secondary development after the ABAQUS software simulations true triaxial discussions principal stress coefficient b. Under undrained conditions, with the main stress factor is increased, the peak stress will increase small amplitude. But little impact. And in drainage conditions, the growth rate of the stress-strain curve as the main stage will stress coefficient b increases faster, but little change in a stable.