Development of non-smooth fracture surface by cracks propagating in heterogeneous and particulate materials

With the Blue Shift method one can infer the so-called localisation exponent of the power-law growth of the numbers of the signals with time. The integer part of it distinguishes different types of the damage (process) zone. The fractional part of it can be interpreted as a signature of fracture branching. The fracking experiment and operation show that in most cases the integer part equals to 1 at active loading stages and turns to 0 at shut-in. This suggests that fracture grows in all directions in its plane, while at shut-in the growth turns into unidirectional. The presence of fractional part of the localisation exponent indicates fracture branching. The damage accumulation in the rock slope in an open-pit mine only shows planar damage zone branching with branches growing in all directions in their respective planes by forming constant process zones. The PFC2D test of uniaxial compression shows unidirectional growth with branching.