Characteristics of excavation disasters and long-term in-situ mechanical behavior of the tunnels in the China Jinping Underground Laboratory
LI Shaojun1, ZHENG Minzong1,2, QIU Shili1, YAO Zhibin3, XIAO Yaxun1, ZHOU Jifang4, PAN Pengzhi1
1. State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China; 3. Key Laboratory of Ministry of Education for Safe Mining of Deep Metal Mines, Northeastern University, Shenyang 110819, China; 4. Yalong River Hydropower Development Co., Ltd., Chengdu 610051, China
Abstract:The construction of deep high-stress tunnels can face various problems such as rockbursts, rib spalling, and tunnel collapse. The 2 400 m deep China Jinping Underground Laboratory (CJPL-II) is currently the world's largest buried laboratory. The construction of this group of tunnels included field monitoring and numerical analyses of the mechanical response of the rock around the tunnels, such as the deformation, stresses and microseismic events. The complex geological conditions are analyzed to predict tunnel disaster characteristics and the long-term in-situ mechanical response of the rock. The results show that the surrounding rock mass deformation is larger on the north side walls of laboratory 1# and laboratory 4# with a maximum deformation of 83.7 mm. The maximum rock bolt stress is 530 MPa. The rock mass deformation tended to become stable about three months after completion of the excavation. The excavation damage zone revealed by elastic waves and a borehole camera is generally 0.8~3.5 m. The results also show that the internal fractures in the surrounding rock mass evolve with the excavation with zonal disintegration. The high strength, good integrity rock has a small fracture zone while the low strength, poor integrity rock has a large fracture zone. The results also show that there is more micro-seismic activity in the completed rock mass tunnel and the area around the fault. The intensity of the microseismic activity in each laboratory tunnel during excavation was highest for 8# and decreased to 8#, 7#, 4#, 3#, 5#, 6#, 1#, 2# and 9# as the lowest. After excavation, the microseismic activity in each tunnel gradually decreased. The CASRock software analysis showed the high stresses and large relaxation depth of the southern arch shoulder and sidewall after excavation and unloading that created high-risk areas. The results provide direct support for disaster warning system development, stability assessments, dynamic designs, and long-term safe tunnel operation for safe construction of high-stress, deep tunnels with similar geological conditions.
李邵军, 郑民总, 邱士利, 姚志宾, 肖亚勋, 周济芳, 潘鹏志. 中国锦屏地下实验室开挖隧洞灾变特征与长期原位力学响应分析[J]. 清华大学学报(自然科学版), 2021, 61(8): 842-852.
LI Shaojun, ZHENG Minzong, QIU Shili, YAO Zhibin, XIAO Yaxun, ZHOU Jifang, PAN Pengzhi. Characteristics of excavation disasters and long-term in-situ mechanical behavior of the tunnels in the China Jinping Underground Laboratory. Journal of Tsinghua University(Science and Technology), 2021, 61(8): 842-852.
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