Why the drained/undraned saturated materials couldn't be used for slope failure simulation due to soil strength reduce?

[zhangfengeo]

Hi,I want to simulate the slope failure due to abrupt strength reduce,so I built a slope model with slope gradient =45°,the material parameter are specified as c'=12.38kPa,φ‘=15°,E=100MPa,possion rate=0.3. Firstly I chose MC model with undrained effective stress saturated material ,the first loadstep is to create initial stress state by appling gravity load,then calculated,then modified the loadsteps num=80 and turn quasistatic convergence off in CPS002 file. But the results show that the displacement and deviatoric strain nearly equal to 0.The MC model with drained saturated material shows a similar result like this.

Then I chose MC model with fully coupled saturated material,the first loadstep is to create initial stress state by appling gravity and specify a higher soil strength(c'=123.8,φ'=15°),then calculated,then modified the loadsteps num=100,turn quasistatic convergence off in CPS002 file,and modified the material strength in GOM file equal to c'=12.38,φ'=15°.Differently the result show obvious displacement and deviatoric strain.




It seems the full coupled material is correct for this case,So why the drained/undraned material couldn't be used in this case,and why there exsit such a big difference between the full coupleed material type and nomal material types,as there are no change of hydrualic condition in this model,and I didn't set a water level.

[zhangfengeo]

I recaculate the model again and found that the undrained saturated material MC can be used to create the stress field of the slope,cuz last time I forgot to spycify the vaule of undrained possion ratio in the drained saturated material MC model.but the drained material still cant't be used to creat the stress field,it's strange.