Patterns of Influence of Parallel Rock Fractures on the Mechanical Properties of the Rock–Coal Combined Body

Hydraulic fracturing of a roof can attenuate the strong mineral pressure and stress transfer by creating series parallel artificial fractures in it, different forms hydraulic have effects on attenuation effect coal rock system. In this regard, study investigated influence law pre-cracks mechanical properties rock–coal combined body through PFC2D numerical simulation, following conclusions were obtained. Parallel significantly affected body. The stress–strain curve coal–rock assemblage containing changes reductions peak strength, strain, elastic modulus, crack initiation stress. closer angle θ between single set horizontal is to 30°, longer length, L, lower strength specimen, modulus elasticity, Macroscopic damage patterns are given for sets parameters, with sample damage, damage; divided into three modes fracture when pressurized. These cracking sample, simultaneous pre-crack tips samples, samples.