Instability Modes and Stability Analysis of Perilous Rock Groups with Control Fissures Under the Conditions of Excavation and Rainfall

Influenced by external factors, perilous rock is prone to evolve into geo-hazard. Prevention and control design of geo-hazard is closely related to the correct quantitative analysis of the stability as well as in-depth study of the instability mode. As the main rock, limestone is widely exposed in the study area, which has resulted in perilous rock groups with control fissures at trailing edges. Monitoring data and investigation reveal that rainfall and roadway excavation are the main external inducing factors of perilous rock groups. Representative geo-mechanical models of the perilous rock groups were constructed based on the engineering geological investigation. Their mechanical behaviour affected by different inducing factors was analyzed, and the instability mode under the most dangerous condition was examined by the numerical simulation based on the discrete element theory. It is found that influenced by rainstorm and excavation, the overall instability mode of perilous rocks with specific geological structure can be divided into sliding and toppling tensile-shear failure. Furthermore, the overall stability of perilous rocks corresponding to these two modes was quantitatively analyzed using the limit equilibrium and fracture mechanics theories. The calculation results are considered to be reasonable and reliable due to the good agreement of the calculation theories with the failure mechanism of perilous rocks.