Research On The Triple-shear Unified Constitutive Model For Saturated Over-consolidated Clay And The Secondary Development For ABAQUS

Over-consolidated clays refer to those characteristics demonstrated after ever receiving greater than the current weight of the soil, so over-consolidated clays has high intensity and low porosity, typically exhibiting the speciality of softening and dilatancy behavior. Considering that at the present stage most of constitutive models of clays widely used are based on the test of reconstituted soil,then we can use the remolded over-consolidated clays as the research object. According to the stress transformation and through different1 I and ? to control soil failure ratio M and with triple-shear unified theory as the failure criterion we propose the sub-loading yield surface modified cam-clay model and then build the triple-shear unified constitutive model for over-consolidated clay. Hence, this model has the comprehensive advantages of triple-shear unified intensity theory and the sub-loading yield surface modified cam-clay model.This paper take saturated over-consolidated clays as research object and gives a brief introduction on the triple-shear unified intensity theory and the sub-loading yield surface modified cam-clay model. In the yield equation of the subloading yield surface modified cam-clay model,we can effectively introduce triple-shear unified theory as the failure criterion and gain the yield equation of elasto-plastic constitutive relation of over consolidated clays based on triple-shear unified intensity theory.The three parameters of1 I,2J and3 J are used to interpret the triple-shear unified constitutive model for over-consolidated clay and then the elastic-plastic constitutive matrix of the finite element method is derived from it.This paper introduces the finite element method of this model. With the user of ABAQUS self-defined material subroutine interface UMAT and a subroutine of this model developed in the Fortran language, we simulate the tri-axial compression test under the different confining pressure and different drainage conditions, and compare the results with the theoretical resolution of this model,and then discuss the effect of the intermediate principal stress on this model. It shows that the results of the developed subroutine and the theoretical solution are almost the same. Under different drainage conditions, the subroutine can effectively reflect the mechanical properties of the over-consolidated soils with different over-consolidation ratios, such as strain softening shear shrinkage and dilatancy.Finally the multiple unit models of over-consolidated soil tri-axial compression test are established and compared respectively with the test data.The result has good consistency within. Moreover the user material subroutine interface UMAT can expand the database of ABAQUS software. It can provide some references on the second development of ABAQUS for geo-technical researchers.