| In relatively hard formations,rock masses are divided into spatially shaped rock blocks of different shapes due to the presence of structural planes.In the natural state,the spatial rock blocks of various shapes maintain the original static balance state.When the slope or the underground cavern is excavated and the like,the rock mass on the air surface breaks the original static equilibrium state,which causes some rock mass to slide along the structural surface first,and then causes the chain reaction.This in turn affects the safety of the entire rock mass project.Because the underground caverns are in a relatively complex geological environment,the research is difficult,so the analysis and research on the stability of the surrounding rock of the underground caverns is less.At present,the stability analysis of the surrounding rock of underground caverns is mostly based on the software Unwedge.The software can only calculate the size and stability of the cavity block,but the specific location cannot be determined.In this paper,the underground caverns of Shuibuya Hydropower Station are taken as research objects.Based on the geological catalogue of the previous caverns and the geological survey of the site,the stability of the underground caverns is evaluated by the block theory to determine the specific location of the caverns.And the way of destruction,providing reasonable advice for support.Based on the geological survey results of each cavern,the groundwater leakage of the hydropower station is further analyzed.Through the analysis of the data of the groundwater monitoring point and the piezometric tube of each flat hole for many years,the groundwater leakage in each area of the hydropower station is determined,so that it can be found.Reasons for leakage,and then take measures to reduce the occurrence of leakage and ensure the long-term safe operation of the hydropower station.The specific research contents and results are as follows:1)Combining the block theory and on-site geological survey to analyze the stability of surrounding rock of each cavern,and determine the three ways of local damage of underground caverns in this area: There are only underground underground due to the formation of unstable blocks by structural plane cutting.Plant 1# construction branch hole;At the same time,there is still a section in the branch hole that is cut by the regional crack surface,which causes the cavern to collapse under the action of excavation forming the air surface;Widely distributed in each cavern The phenomenon of peeling off due to water seepage.2)According to the collapse phenomenon at the site of the cavern,it is determined that the No.4 key block consisting of T9,F3 and T7 structural planes in the 1#construction branch of the underground powerhouse is located at the top of the cavern,which is in an unstable state and may fall off.The cavern also exists because the gently sloping rock layer is cut by the regional fissure surface,and the vacant surface is formed under the excavation effect,which causes the cavern to collapse.Using the strike extension of the fracture surface in this area,it is predicted that the specific location of the collapse may occur in the cavern.3)Stability analysis and on-site investigation of the five major areas of the hydropower station.The drainage holes in the Dayantang landslide area on the left bank are basically not formed by the structural plane,but due to the partial passage of the cover layer,local landslide phenomenon will occur in the cavern,fault The shear zone is densely developed,which makes the rock mass integrity poor and the stability of the cavern is low.The stability of the surrounding rock of the elevation grouting adit is high and the rock mass is good.There is no block formed by the combination of structural planes in each elevation drainage hole of the maya high slope,but the unloading fissures of the Maya high slope pass through the 230 and 260 drainage holes,which causes large cracks in the cavern,the stability of the rock mass is reduced,and the rest of the rock mass is at Stable state,no damage.In addition to the 1# construction branch hole,the surrounding rock of each floor of the plant has high stability.4)Conducting water seepage surveys in various areas of hydropower stations,combined with multi-year data analysis of each cavern monitoring point: the leakage of grouting holes in the left and right banks mainly occurs on the side close to the dam site,mainly the osmosis of the reservoir water to the slope;The water seepage of the landslide is mainly caused by the deformation of the landslide.The water source comes from rainfall.The seepage of the underground powerhouse on the right bank is mainly from the large crack generated by the unloading of the Maya slope.The rain enters the underground powerhouse through the crack and is discharged through the drainage hole of the underground powerhouse.By tracking the extension of the surface of Zoujiagou and the location of the underground karst channel,it is judged that the water seepage in the grouting hole at Zoujiagou mainly comes from the surface water of Zoujiagou.Due to its topography,the sides of the mountain are caused.The surface water gathers here and enters the grouting hole along the surface fissure.According to the on-site investigation of the monitoring data,the grouting curtain appeared in the curtain in July 2014.Carry out detailed geological survey on the water spray point of the 2# oblique traffic adit on the right bank,and use the flow monitoring data of the water volume for many years,combined with the trend of the regional fault and the karst channel exposed on the surface to judge the leakage.Mainly due to rainfall and reservoir water,the rainwater mainly enters the 2# oblique traffic adit through the large east-west fault of the surface.The reservoir water is mainly through the grouting curtain near the F2 fault through the 350 m grouting flat hole on the right bank,passing through the karst channel.2# oblique traffic hole. |
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