  A phase field model for fluid-driven dynamic crack propagation in poroelastic
media is proposed. Therefore, classical Biot poroelasticity theory is applied
in the porous medium while arbitrary crack growth is naturally captured by the
phase field model. We also account for the transition of the fluid property
from the intact medium to the fully broken one by employing indicator
functions. We employ a staggered scheme and implement our approach into the
software package COMSOL Multiphysics. Our approach is first verified through
three classical benchmark problems which are compared to analytical solutions
for dynamic consolidation and pressure distribution in a single crack and in a
specimen with two sets of joints. Subsequently, we present several 2D and 3D
examples of dynamic crack branching and their interaction with pre-existing
natural fractures. All presented examples demonstrate the capability of the
proposed approach of handling dynamic crack propagation, branching and
coalescence of fluid-driven fracture.
