Dynamic failure modes of large-scale underground caverns with complex geological structures

Abstract

Rock masses are often exposed to dynamic loads such as earthquakes and mechanical disturbances in practical engineering scenarios. The existence of underground caverns and weak geological structures like columnar jointed rock masses (CJRMs) and interlayer shear weakness zones (ISWZs) with inferior mechanical properties, significantly undermines the overall structural stability. To tackle the dynamic loading issues in the process of constructing subterranean caverns, a programmable modeling approach was utilized to reconstruct a large-scale underground cavern model incorporating ISWZs and columnar joints (CJs). By conducting dynamic simulations with varying load orientations, the analyses focused on the failure patterns, deformation characteristics, and acoustic emission activity within the caverns. Results revealed that the failure modes of the underground caverns under dynamic loading were predominantly tensile failures. Under X-direction loading, the failed elements were mainly distributed parallel to the CJs, while under Y-direction loading, they were distributed parallel to the transverse weak structural planes. Furthermore, the dynamic stability of the overall structure varied with the number of caverns. The dual-cavern model demonstrated the highest stability under X-direction loading, while the single-cavern model was the least stable. Under Y-direction loading, the cavern stability increased with the number of caverns. Importantly, different weak structures affected the dynamic response of caverns in different ways; the CJRMs were the primary contributors to structural failure, while ISWZs could mitigate the rock mass failure induced by CJs. The findings could offer valuable insights for the dynamic stability analysis of caverns containing CJRMs and ISWZs.