Micro-macro damage, deterioration and cracking of heterogeneous composite rock masses with non-penetrating cracks under uniaxial compression

Rock masses with non-penetrating cracks are widely found in nature. Their mechanical behavior plays a key role in rock engineering applications. However, previous studies have concentrated on the single lithologic layer, and few studies have reported the crack coalescence mechanism in heterogeneous composite rock mass with non-penetrating cracks (HCRC). In this study, uniaxial compression tests were performed on HCRC by discrete element numerical simulation experiments. Through the uniaxial compression simulation tests, the stress–strain variation and acoustic emission (AE) characteristics of HCRC are revealed. The instability and failure characteristics, energy evolution law and crack coalescence process of HCRC are also studied. And the influence of the crack numbers and crack positions (in weak body or strong body) on the mechanical behavior and failure processes in heterogeneous composite rock mass is investigated. The results show that the mechanical properties of HCRC are not all weakened with the increase of the crack numbers. As the number of cracks increases, the failure modes of the HCRC changes from brittle failure to ductile failure. The number of cracks will regulate the relative relationship between the strength of the two bodies of heterogeneous composite rock masses, so the crack coalescence forms, instability forms and failure characteristics of the HCRC will also change accordingly. If the number of cracks in the weak body is large, the damage of the HCRC mainly occurs in the weak body. The strong body produces a rebound energy release to the weak body, accelerating the destruction of the weak body. At this time, the overall strength of the HCRC is low. Conversely, increasing the number of cracks in a strong body will weaken the strength of the strong body. At this time, the strength difference between the strong body and the weak body decreases. The HCRC shows that the overall bearing capacity is not lower but becomes stronger. The research results provide a theoretical reference for the stability and disaster prevention of jointed rock mass engineering.