Unfilled joint rock in the surrounding rock mass of a huge underground cave in Longtan Hydropower Project was carried out shear creep experiment. Compared with the short-term shear strength parameters gotten by rapid shear experiment, the long-term shear strength parameters have some reduction. Moreover, the sensitivity of cohesion on the time is higher than that of internal friction angle. Based on shear creep curves of joint rock, five-component visco-elastic shear creep model is put forward to identify the curves that show the visco-elastic creep behaviors. Then by connecting Non-linear Visco-plastic Body (NVPB) and five-component visco-elastic shear creep model in series, we construct a new seven-component non-linear visco-elasto-plastic shear creep model of rock. Then using complete accelerative shear creep curve of joint rock, proposed seven-component non-linear shear creep model of rock is carried out the identification. The comparison between the shear creep model and experimental result shows that proposed non-linear shear creep model is right and reasonable.
Joint rock is a kind of complex medium in rock mass engineering, which possesses the property of heterogeneity, anisorropism, and noncontinuity, etc. The strength, deformation, failure and creep etc. of joint rock will has a direct effect on the design, construction, operation, stability and reinforcement of rock mass engineering. At the present time, there are some study results on the creep behavior of rock(Maranini, E. & Brignoli, M. 1999); (Fujii, Y. er al. 1999); (Li, YS. & Xia, C.c. 2000); (Shao, J.F er al. 2003); (Dahou, A. ct al. 1995); (Yang, C.H. et al. 2003a,b); (Yang, C.H. et al. 2000); (Yang, C.H. et al. 2002). However, main results still focus on the investigation on the creep behavior of rock material. Creep behavior of joint rock has great difference from that of rock material. Existing many papers have shown that creep law of joint rock are carried out less analysis. Moreover, the experimental results on shear creep of joint rock are less, which is an important flaw on the investigation of creep behavior. Therefore, experimental investigation on creep behavior of joint rock not only have important practice meanings for analyzing the creep behavior of whole rock mass engineering, but also bring forward the base for theoretical study and numerical analysis of rock creep behavior.
Longtan Hydropower Project is located in the upper Hongshui River, 15 km from Tian'e County of Guangxi Zhuang Autonomous Region. The main function of the huge Station is power generation, incorporated with flood control, navigation, etc. The storage capacity is 27.3 billion m3 and the custom design pool level is 400 m. The total installed capacity is 5400 MW and the RCC gravity dam with the height of 218 m will be constructed. The stratum of underground cave is mainly sandstones. Geological condition of rock mass is more complex, and faulted bedding plane develops more. For subjected to the effect of erosion, the maximum main stress of rock mass ranges from 6 MPa to 9 MPa.
