The first slope stability calculation is performed with a, non-associative, Mohr-Coulomb elasto-plastic material law. The gravity load is applied slowly to create the initial state. Then four excavations are performed by removing elements. The remaining slope is still stable. The first plot shows the vertical stresses after the four excavations.

Now an extra loading on the slope is simulated, by imposing slowly a body force parallel to the slope. This body force might mimic a slope parallel force induced by groundwater flow after heavy raining. The extra force triggers instability of the slope. The instability analysis has been performed dynamically, so that mass terms lead to a more stable numerical convergence behavior. Furthermore, an automatic time stepping scheme is used, which reduces time steps when the instability shows up. The next two plots show the size of the velocity and the size of the plastic strains respectively.

Here is the Inputfile for the Mohr-Coulomb calculation.