Simulating hydro mechanical effects in rock deformation by combination of the discrete element method and the smoothed particle method

• Smoothed Particle (SP) can be used to interpolate Discrete Element Method (DEM) results to continuum scale.
• The method allows for modeling of rapid deformations of saturated rock.
• The method complies to the effective stress theory.
• The method properly models strain rate effects in both consolidated and unconsolidated compression tests.

The discrete element method (DEM) has been used successfully to simulate rock failure. However, when considering the deformation of fluid-saturated rock, the DEM lacks the contribution of the fluid pressure. The presence of a (pore)-fluid can affect the effective stress state, which might result in a change in some of the mechanical properties of the rock, e.g. strength and modulus. Additionally, saturated rock is more susceptible to strain rate effects.An extension to DEM is presented in which the effective stress theory is embedded by coupling the DEM with a pore pressure diffusion process. This is achieved by interpolating the discrete properties of the DEM to a continuum by using a smoothed particle approach (SP). The model is able to predict the strengthening/weakening of a rock with respect to the amount of fluid drainage that has been allowed. To demonstrate the validity of the model, several simulations of tests under different loading conditions are conducted and the results are compared with experimental data from literature. The agreement between theory and experiment is very good.