Unloading performances and stabilizing practices for columnar jointed basalt:A case study of Baihetan hydropower station  

作　　者：Qixiang Fan Xiating Feng Wenlin Weng Yilin Fan Quan Jiang 

机构地区：[1]China Three Gorges Corporation,Beijing,100038,China [2]State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Sciences,Wuhan,430071,China

出　　处：《Journal of Rock Mechanics and Geotechnical Engineering》2017年第6期1041-1053,共13页岩石力学与岩土工程学报（英文版）

基　　金：the financial support from the International Partnership Program of Chinese Academy of Sciences(Grant No.115242KYSB20160017);the Key Project of Natural Science Foundation of China(Grant No.11232014);National Natural Science Foundation of China(Grant No.51379202)

摘　　要：The columnar jointed rock mass(CJR), composed of polygonal cross-sectional columns cut by several groups of joints in various directions, was exposed during the excavations of the Baihetan hydropower station, China. In order to investigate the unloading performances and the stability conditions during excavation of the columns, an experimental field study was performed. Firstly, on-site investigations indicated that the geotechnical problems, including rock relaxation, cracking and collapse, were the most prominent for the CJR Class I that contains intensive joint network and the smallest column sizes.Comprehensive field tests, including deformation measurement by multi-point extensometers, ultrasonic wave testing, borehole television observation and stress monitoring of rock anchors, revealed that the time-dependent relaxation of the CJRs was marked. The practical excavation experiences for the Baihetan columnar jointed rock masses, such as blasting scheme, supporting time of shotcrete and rock bolts, were presented in the excavations of the diversion tunnels. These detailed investigations and practical construction experiences can provide helpful information for similar geotechnical works in jointed rock mass.The columnar jointed rock mass(CJR), composed of polygonal cross-sectional columns cut by several groups of joints in various directions, was exposed during the excavations of the Baihetan hydropower station, China. In order to investigate the unloading performances and the stability conditions during excavation of the columns, an experimental field study was performed. Firstly, on-site investigations indicated that the geotechnical problems, including rock relaxation, cracking and collapse, were the most prominent for the CJR Class I that contains intensive joint network and the smallest column sizes.Comprehensive field tests, including deformation measurement by multi-point extensometers, ultrasonic wave testing, borehole television observation and stress monitoring of rock anchors, revealed that the time-dependent relaxation of the CJRs was marked. The practical excavation experiences for the Baihetan columnar jointed rock masses, such as blasting scheme, supporting time of shotcrete and rock bolts, were presented in the excavations of the diversion tunnels. These detailed investigations and practical construction experiences can provide helpful information for similar geotechnical works in jointed rock mass.

关 键 词：Columnar jointed basalt Diversion tunnels Rock unloading In situ test Hydropower station 

分 类 号：TV223.1[水利工程—水工结构工程]