Rock and Soil Mechanics ›› 2021, Vol. 42 ›› Issue (9): 2556-2568.doi: 10.16285/j.rsm.2021.5194

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Analysis of stress-structural collapse mechanism of columnar jointed basalt under high stress

ZHANG Jian-cong1, 2, JIANG Quan1, 2, HAO Xian-jie1, 2, FENG Guang-liang1, 2, LI Shao-jun1, 2, WANG Zhi-lin3, FAN Qi-xiang3, 4   

  1. 1. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan, Hubei 430071, China 2. University of Chinese Academy of Sciences, Beijing 100049, China 3. China Three Gorges Construction Management Co., Ltd., Chengdu, Sichuan 610041, China 4. China Huaneng Group Co., Ltd., Beijing 100031, China
  • Online:2021-09-13 Published:2021-12-15
  • Contact: JIANG Quan, born in 1978, PhD, Professor, research interests: numerical simulation of underground engineering, large cavern stability, safety and disaster prevention. E-mail:
  • About author:ZHANG Jian-cong, born in 1991, PhD, research interests: columnar joint rock mass mechanical properties and underground cavern stability.
  • Supported by:
    the National Natural Science Foundation of China(U1965205, 5177925) and the International Partnership Program of Chinese Academy of Sciences(115242KYSB20160017).

Abstract: Columnar jointed rock mass with unique joint network structure is a special type of jointed rock mass, which is a binary structure composed of high strength ‘basalt block’ and specific ‘dominant joint’. Relaxation, opening and slippage of columnar jointed surfaces and disintegration of columns occur easily during excavation under high ground stress, which eventually lead to disastrous collapses in columnar jointed rock mass. The construction safety of underground engineering under high stress is severed restricted by it. By combining acoustic wave, borehole camera and other integrated in-situ testing technology and numerical simulation, the mechanism of stress-structural collapse in columnar jointed rock mass under high stress is studied based on multiple columnar jointed rock mass collapses at left bank tailwater connection pipe of Baihetan hydropower station. The proposed controlling measures of excavation and support are also provided. The key of columnar joined rock mass collapse is the redistribution of stress in surrounding rock mass after the excavation and the strong unloading relaxation of columnar joined basalt, which causes the opening of its internal joint surfaces and structural deterioration, result in the disintegration of basalt columns. Thus, the chain catastrophic process of continuous unloading relaxation and progressive collapse of columnar jointed rock mass is induced. The research can provide reference for the prediction and control of deformation and failure of jointed rock masses in underground engineering under high geo-stress.

Key words: high-stress, columnar jointed rock mass, stress-structural collapse, in-situ test, numerical analysis