Mechanical behaviours of sandstone containing intersecting fissures under uniaxial compression

Predicting rock cracking is important for assessing the stability of underground engineering. The effects of the intersecting angle α and the distribution orientation angle β of intersecting fissures on the uniaxial compressive strength and the failure characteristics of sandstone containing intersecting fissures are investigated through laboratory experiments and two-dimensional particle flow code (PFC2D). The relationship between the mechanical properties of sandstone and the intersecting angle α and the distribution orientation angle β is analysed. Crack initiation forms and the final failure modes are then categorised and determined via empirical methods. In addition, the cracking processes of intersecting fissures with different α and β values are discussed. The results show that variations in the peak stress, peak strain, average modulus, and crack initiation stress of sandstone containing intersecting fissures show a "moth" shape in the space of the α-β-mechanical parameters. Two crack initiation forms are identified: inner tip cracking (usually accompanied by one outer tip cracking) and only outer tips cracking. Two failure modes are observed: (1) the main fracture planes are created at the inner tip and one outer tip, and (2) the main fracture planes are formed at the two outer tips. Two main crack evolution processes of sandstone containing intersecting fissures under uniaxial compression are found. Approaches for quickly determining the crack initiation form and the failure mode are proposed. The combination of the determination equations for the crack initiation form and the failure mode can be used to predict the crack evolution. The approach for determining the crack evolution processes is hence proposed with acceptable precision.