Abstract
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.
Highlights
Rock collapse widely occurs in the mountains of the eastern Tibetan Plateau owing to the geomorphic features of active crustal stress and large elevation differences
Mountains based on the above models, we review the criteria of crack initiation, study the crack extension and use XFEM to simulate cracking according to fracture mechanics
We systematically study the influence of length and vertical inclination of a crack on the fracture characteristics of perilous rocks under gravity and the hydrostatic pressure (Table 4)
Summary
Rock collapse widely occurs in the mountains of the eastern Tibetan Plateau owing to the geomorphic features of active crustal stress and large elevation differences. Few studies have clearly addressed the rock collapse mechanism, the character, distribution law, and induced factors of collapse have been well studied in a qualitative or semi-quantitative manner (Ez Eldin et al 2013) These results cannot be used to explain how a collapse develops. The major objective in our paper is to clearly study the rock collapse mechanism in the freeze-thaw zone of eastern Sichuan-Tibet Mountains from a fracture mechanics standpoint with consideration of phase change of water under seasonal fluctuations of surrounding temperatures. We analyzed the various water-heat combinations in different seasons and develop four models to characterize the driving forces of crack growth, including ice gravity, friction, water hydrostatic pressure, ice-induced stress, and their combinations. We calculated the crack initiation and propagation using XFEM and studied different variations on the crack models to explain the rock collapse mechanism under seasonal fluctuations of water and heat. We apply the results to practical examples to demonstrate the new theory of rock collapse
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