Stability Evaluation Of Surrounding Rock Of Water Conveyance Tunnel Of Chemabi Reservoir In Malong County, Yunnan Province

The proposed water conveyance tunnel of CheMabi Reservoir is 29.56km long and the maximum depth is 235m.It is the key water diversion project of Qujing municipality. Due to the large length and throughing the complicated geological conditions of the tunnel, groundwater in part of the hole is rich, so it is easy to cause the deformation or collapse and other destructive problems may be occurred in the excavation in the tunnel. In order to provide a strong guarantee of the project design and the smooth construction, it requires the deep and comprehensive study on the stability of the surrounding rock of the water conveyance tunnel. Therefore, this paper is the study on the stability of the surrounding rock of the water conveyance tunnel of Chemabi reservoir.Based on the data collected from the previous studies of the study area, the topography, lithology, engineering geology and other aspects of the area is deeply investigated and analyzed. Throughing to start research the deformation and destruction characteristics of the water conveyance tunnel of Chemabi Reservoir, We analyzed the influencing factors of the tunnel stability. This study is based on the geological documentation of drill core, then adopts the methods of engineering geological classification,and the engineering rock mass classification to classify the surrounding rock quality of the water conveyance tunnel. The three-dimensional finite difference program FLAC^3D is used to simulate the tunnel excavation and support mode according to the classification results of the surrounding rock. Finally, the selected support method is verified with the software of Geo-geotechnical software.The main conclusions of this paper are:1. The dolomite and the limestone and other hard rock are the type of ? surrounding rock. Generally do not need to support because of the integrity of the rock mass is good.The sandstone and some limestone class etc. are the type of ? surrounding rock and need to support due to the presence of weak interlayers; Most of the shales are the type of ? surrounding rock, because of the rock is very broken and the stability is poor, so it need to support.2. The surrounding rock of the tunnel is the type of IV, which accounts for 54.3% ;the type of V accounted for 29.9%; the type of III accounted for 15.8%?3. The results can be seen through the FLAC^3D numerical simulation:?The elastic plastic deformation is generated around the tunnel after the excavation, in the side wall mainly horizontal displace and roof and floor of tunnel mainly vertical displacement. The distribution of the maximum deformation area of the three types of the surrounding rock is the same, which is in the middle of the wall sides and the roof and floor of the tunnel.?Through simulate surrounding rock in different support ways, it can be concluded that the appropriate support method for all types of surrounding rock types. In the case of lining the same, the row& line space of bolting are:the surrounding rock type of IV is 1.5m * 1.5m; the surrounding rock type of V is 1m * 1m; and get a good support effect diagram. And then use the software to verify the rationale for the supporting program.It shows that the above scheme is economical and feasible.Through the above analysis and study, the comparison of results from the surrounding rock classification and numerical simulation of excavation of water conveyance tunnel can be seen that the results of qualitative analysis and quantitative calculation are basically the same. All of the result reflected the stability of the surrounding rock of the water conveyance tunnel of Chemabi reservoir. In the end, the economical and feasible supporting scheme of the surrounding rock is obtained. The research results will be giving a guiding significance to the design and construction of the water conveyance tunnel of Chemabi reservoir.