Avalanches in dry and saturated disordered media at fracture in shear and mixed mode scenarios

We investigate shear and mixed mode fracture scenarios in inhomogeneous dry and fully saturated porous media with a 2D central force lattice model. For the fully saturated case we adopt the extended Biot's theory. The bars of the lattice break only under traction which is a common assumption in lattice models for rocks. The breaking process is simulated with a continuous damage model where after a partial failure event, spring elements are assigned a new failure threshold sampled from a uniform distribution. We investigate avalanche behaviour of the damaging events as well as the pressure evolution and the existence of pressure jumps linked to the breaking events in the disordered medium. In pure shear fracture the behaviour differs from that observed previously with the same model for prevailing tearing conditions. Power law distribution of the damaging events does not hold anymore and the overall behaviour is brittle without intermittent crack tip advancement. Pressure fluctuations are however observed. In a mixed mode scenario some of the features observed under prevailing tearing conditions are recovered such as the overall elasto-plastic behaviour. An estimate of the time needed for the internal rearrangements within a loading step is given.