Fracture of rocks in the mountains of Southeast Tibet under hydrothermal conditions at different elevations

Abstract

Significant changes in the hydrothermal conditions in the mountains of Southeast Tibet result in frequent propagation of cracks and disintegration of rock masses. The mechanism that drives this fracturing process might vary considerably depending on elevation. In this work, we employed computational fracture mechanics to study three different fracture mechanisms in which ice or water drives crack propagation. These case studies were corroborated by field observations at low, intermediate, and high elevations. We employed a novel extended finite element method (XFEM), which could be used to propagate cracks without remeshing, to study the effects of the driving forces, crack geometry, and characteristics of perilous rocks. It was found that stress intensity factors induced by freezing of water or by thermal expansion of ice were much higher than induced by hydrostatic pressure, and they resulted in smaller critical crack lengths and tinier collapses at intermediate or high elevations. Moreover, the effects of crack inclination and propagation could have considerable impact on rock collapse. In particular, long cracks with large outward inclination located near the free surface of perilous rocks would tend to fracture easily.