Fracture mechanism of rock collapse in the freeze–thaw zone of the eastern Sichuan–Tibet Mountains under seasonal fluctuating combinations of water and heat

In the freeze–thaw zone of the eastern Sichuan–Tibet Mountains, the phases of water in cracks show strong seasonal variations, which significantly affect the stability of perilous rocks. However, few studies have clearly addressed the role of water/ice in crack development from a fracture mechanics viewpoint to explain the seasonality of rock collapse. In this study, we built physical models from a fracture mechanics viewpoint to calculate water-freezing stress, hydrostatic pressure, and their combinations induced by water/ice in cracks and show the crack propagation mechanism under temperature fluctuations in different seasons in mountainous regions. On the basis of these models, we calculate fracture conditions, simulate the crack process, and illustrate the rock collapse mechanism in different seasons using the extended finite element method. The results indicate that different phases of water, which induce stress under spatiotemporal fluctuations of temperature, determine the various propagation styles and influence what kind and when a collapse will occur. The collapse of fractured rocks in different seasons generally results from rock damage accumulation owing to the initiation, propagation, and connection of primary cracks under freezing stress or hydrostatic pressure or different combinations of these processes.