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| Investigation on deformation and cracking behaviors and stability analysis of surrounding rock mass of underground main powerhouse of Shuangjiangkou hydropower station during preliminary excavation |
| ZHANG Di1，2，LI Shaojun1，XU Dingping1，LI Yonghong3，JIANG Quan1，XIA Yuelin1，2，LI Zhiguo3 |
| (1. 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. PowerChina Chengdu Engineering Corporation Limited，Chengdu，Sichuan 610072，China) |
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Abstract During the preliminary excavation of the main power house of Shuangjiangkou hydropower station，the brittle failure phenomenon is obvious，and the surrounding rock deformation of the area affected by porphyry veins is prominent. To this end，after the preliminary excavation of the main powerhouse，a comprehensive analysis is conducted on deformation and cracking behaviors of surrounding rock and stability of the cavern，which consists of monitoring of surrounding rock deformation by multi-point displacement meters，imaging observation of surrounding rock fractures by borehole camera，numerical simulation of excavation process and effects on local site deformation of the porphyry vein based on 3DEC software. A novel method for evaluating the stability of caverns based on the surrounding rock loosening zone and the cross-sectional area of the cavern is proposed. The results show that，after the first floor excavation，the deformation of the surrounding rock of the main power house is small as a whole，but the top arch sinks relatively largely. The time-dependent deformation characteristics of the hard granite surrounding rock are not obvious. The surrounding rock deformation is mainly affected by the excavation driving face，and the control range of the excavation face to the deformation of the cave segment affected by the porphyry veins is about 1.5 times the cave span. In addition，there are cracks in the shallow and deep parts of the surrounding rock after excavation，and the cracking phenomenon at the junction of the veins and homogeneous rock is serious. Excavation unloading causes the slip of the upper plate of the porphyry veins，which results in shear deformation of the top arch of the cavern. It is very effective to add anchor cables that completely penetrates the porphyry veins，which significantly improves the stability of the relevant tunnel sections. The research results will provide an important basis for both the optimization of the subsequent excavation and support scheme of the hydropower station and the selection of reinforcement measures for local instability.
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2021, Vol. 40 
