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Geoscience ›› 2021, Vol. 35 ›› Issue (01): 114-125.DOI: 10.19657/j.geoscience.1000-8527.2021.018

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In-situ Stress Measurement and Its Application of a Deep-buried Tunnel in Zheduo Mountain, West Sichuan

XU Zhengxuan1,2(), MENG Wen3,4(), GUO Changbao3,4, ZHANG Peng3,4, ZHANG Guangze1, SUN Mingqian3,4, CHEN Qunce3,4, CHEN Yu1   

  1. 1. China Railway Eryuan Engineering Group Co.,Ltd.,Chengdu, Sichuan 610031, China
    2. Southwest Jiaotong University, Chengdu,Sichuan 610031, China
    3. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
    4. Key Laboratory of Neotectonic Movement and Geohazard, Ministry of Land and Resources, Beijing 100081, China
  • Received:2020-10-01 Revised:2020-11-05 Online:2021-02-12 Published:2021-03-12
  • Contact: MENG Wen

Abstract:

Characteristics of present stress state at a deep-buried tunnel in Zheduo Mountain (west Sichuan) are analyzed based on in-situ stress measurement results at 196-650 m depths using the hydraulic fracturing me-thod. The measured results show that the stress state is dominated by horizontal principal stress, which increases linearly with depth and with higher gradient than the Chinese mainland background value. Reverse stress regime (SH>Sh>Sv) is dominant overall within the measurement depth. The stress-release zone is at 389.50-560.50 m depth, and the stress regime is mainly strike-slip with relative principal stress magnitude of SH>Sv>Sh. The lateral pressure coefficients and the ratio of maximum and minimum horizontal principal stress corresponds approximately with the variation characteristics of Chinese mainland. The fracture impression results reveal that the maximum horizontal principal stress is predominantly WNW, consistent with the regional stress field and mechanical mechanism reflected by the surrounding active faults. Stress field in the study area is mainly controlled by the ongoing India-Asia continent-continent collision and the compressive tectonics from the growing Tibetan Plateau onto the rigid Sichuan Basin. The test borehole is nearly critically stressed in the current stress state. The optimal-orientated plane or special section of the exiting faults may experience instability sliding with the continuous stress accumulation. Subsequently, tunnel stability from the in-situ stress perspective is discussed. The results reveal that the deep-buried tunnel favors medium-strong rock-burst due to strong in-situ stress state and deep burial, and the optimized design and constructive protection should be focused.

Key words: hydraulic fracturing, in-situ stress measurement, stress state, fault frictional sliding, deep-buried tunnel, stability

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