  We present a phase field model (PFM) for simulating complex crack patterns
including crack propagation, branching and coalescence in rock. The phase field
model is implemented in COMSOL and is based on the strain decomposition for the
elastic energy, which drives the evolution of the phase field. Then, numerical
simulations of notched semi-circular bend (NSCB) tests and Brazil splitting
tests are performed. Subsequently, crack propagation and coalescence in rock
plates with multiple echelon flaws and twenty parallel flaws are studied.
Finally, complex crack patterns are presented for a plate subjected to
increasing internal pressure, the (3D) Pertersson beam and a 3D NSCB test. All
results are in good agreement with previous experimental and numerical results.
