Secondary Development Of Subloading Yield Surface Modified Cam-clay Model In ABAQUS And Its Application

For its powerful nonlinear calculation function, general finite element softwareABAQUS is widely used in the field of geotechnical engineering. In its ownmaterial library, the modified Cam-clay model based on the Critical state soilmechanics is usually chose to predict the mechanical behavior of normallyconsolidated soil in geotechnical engineering. However, the modified Cam-claymodel is difficult to describe the mechanical properties of overconsolidated soil.Subloading yield surface modified Cam-clay model, with two yield surfaces, candescribe the stress-strain behavior of overconsolidated soil through the change ofsubloading yield surface, which makes up the shortage of the constitutive model thatowned by ABAQUS. In this paper, the main works are as follows:1. The expressions of elastoplastic constitutive relation and the stress-strainupdating formulas for the secondary development are derived based on the theory ofsubloading yield surface modified Cam-clay model. With the user materialsubroutine interface UMAT, a subroutine of the subloading yield surface modifiedCam-clay model is developed, by using the FORTRAN language and the explicitforward Euler integral algorithm, which can expand the material library ofABAQUS software.2. Using the UMAT subroutine, triaxial compression tests under drainedcondition to the single cell model are conducted under different incremental steps.Compared with the modified Cam-clay model owned by ABAQUS, it can be foundtha that the UMAT subroutine has higher precision and better stability. Through thesimulation of triaxial compression test under the different confining pressure anddifferent drainage conditions, the results are compared with the theoreticalresolution of this model. It shows that the results of the developed subroutine andthe theoretical solution are almost the same. Under different drainage conditions, thesubroutine can effectively reflect the mechanical properties of the overconsolidatedsoils with different overconsolidation ratio, such as strain softening and shearshrinkage, dilatancy, etc.3. The triaxial compression tests of overconsolidated soil and theloading-unloading process test are simulated. The developed UMAT subroutine ismore effective in predicting the progressive change of stress during deformation.Compared to the modified Cam-clay model, it has a big advantage.4. The multiple unit models of overconsolidated soil triaxial compression testand the foundation consolidation settlement are established. Compared respectively with the test data and the modified Cam-clay model owned by ABAQUS, the resulthas good consistency. It suggests that the subroutine can describe the mechanicalproperty of overconsolidated soil accurately and the subroutine is suitable for thecalculation of the foundation settlement...