Research On Surrounding Rock Stability Of Surge Chamber In Danba Hydropower Station

The length of the diversion tunnel of the Danba Hydropower Station from the inlet to the upstream surge tank is about 16.7km,the minimum spacing between the surge chambers is 100 m,the crustal stress is more than 20 Pa,and it has characteristics of deep burial?long hole line?large hole size and high crustal stress.Accurate evaluation of the stability of the surrounding rock of the tunnel is an indispensable condition for economically and rationally carrying out the design of the surrounding rock support,the rapid and safe construction and the safe operation of the Danba Hydropower Station.Based on the geological survey report,the paper analyzes the basic characteristics of the engineering geological conditions of the Danba Hydropower Station,and uses the multiple regression as a mathematical tool to invert the 3D geostress field of the engineering area.,The transverse isotropic strain softening model of the surrounding rock is established and the mechanical parameters in the model are determined.Finally,the three-dimensional geological model of the surge tank of Danba Hydropower Station is established by using FLAC3 D,and the stress and strain of surrounding rock after excavation under natural conditions are simulated.The main work of the paper and conclusions are as follows:Based on the measured geostress values of four boreholes,the original geostress field of the Dangba hydropower station is analyzed by numerical inversion method.The soft rock and hard rock are obtained at 1940 m and 2040 m The principal stress value and the main direction of the stress field in the range.The uniaxial compressive strength of the quartz mica schist in the saturated rock and the dry state is obtained by using the uniaxial compressive strength of the surrounding rock in the indoor uniaxial compression experiment.The softening characteristics of the water are analyzed.The influence of the face on the strength of the surrounding rock is studied by the conventional triaxial experiment.The cohesion and the internal friction angle of the surface are obtained.According to the displacement vector diagram,combined with the plastic zone and the shear strain and the results of the indoor test,the fractal direction of the damage of the quartz mica schist is analyzed by FLAC3 D numerical software.The numerical simulation of the model is carried out.The applicability of the transversely isotropic strain softening model to simulate the mechanical response of quartz mica schist.The numerical simulation of the surrounding rock of the surge tank of Danba Hydropower Station is carried out by FLAC3 D numerical software.The displacement of the surrounding rock at the middle,bottom and dome of the surge chamber is calculated.According to Hoek deformation degree evaluation method,It is better,but the depth of plastic deformation of the surrounding rock in the dome is still large.It is suggested that the long anchor should be used to strengthen the area.