Fracture of rocks in the mountains of Southeast Tibet under hydrothermal conditions at different elevations
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ORIGINAL PAPER
Fracture of rocks in the mountains of Southeast Tibet under hydrothermal conditions at different elevations Yong Wu 1,2 & Yongxiang Wang 3 & Waisman Haim 3 & Siming He 1,2 & Xinpo Li 1,2 Received: 27 December 2019 / Accepted: 8 April 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
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. Keywords Rock collapse . Fracture mechanics . Water–heat combination . Crack models . Mountains of Southeast Tibet . XFEM
Introduction In the mountains of Southeast Tibet, collapses leading to rock avalanches occur frequently. In association with the global climate warming of the previous century (Hore et al. 2018), many huge rock collapses have occurred in the Himalayas. Some of these collapses have induced serious secondary disasters such as debris flows, barrier dams, and spot floods that have resulted in heavy loss of human life and substantial property damage. For example, in 1959, a rock collapse with volume of 107 m3 occurred in Baga (Tibet), which blocked the Chayu River and subsequently caused flooding in seven Indian provinces (Dongtao et al. 2004). In 2000, a large
* Yong Wu [email protected] 1
Key Laboratory of Mountain Hazards and Earth Surface Process, Chinese Academy of Sciences, Chengdu 610041, China
2
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences, Chengdu 610041, China
3
Department of Civil Engineering & Engineering Mechanics, Columbia University, New York, NY 10027, USA
volume (> 108 m3) of rock dislodged from a mountain and blocked the Yigong River (Tibet), which resulted in flooding that killed 97 people following the failure of a nearby dam (Xu et al. 2012). In 2017, approximately 4.3 × 106 m3 of rock detached from a steep hillslope above the village of Xinmo (China), which resulted in 64 buried houses, 10 casualties, a
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