Study On Rock Mass Structure Characteristics Of Upper Reservoir Of Wuyue Pumped Storage Power Station

The Wuyue Pumped-storage Power Station is planned to be built in Yinpeng Township,Guangshan County,Henan Province.The scale of the project is second-class（2）type.The power station has now entered the construction stage and is expected to be completed and put into operation in 2025.The lithology of the upper reservoir area of the power station is mainly red,off-white medium-grain monzonitic granite in the late Yanshan period(γ₅^3-1).Affected by internal and external geological forces,a large number of intricate joints and fissures have developed in the reservoir area,which complicates the structure of the rock mass and has a certain impact on the stability of the rock mass.It is very easy to cause leakage problems in the pumped storage power station and threaten the safety of the power station..In order to avoid or reduce the loss of life and property of the people in the upper reservoir area,this article takes the upper reservoir area of Wuyue Pumped-storage Power Station as the research object to study the rock mass structure characteristics of the upper reservoir area.The main research contents and results are as follows:（1）The"Specification for Geological Survey of Hydropower Engineering"（GB50287-2016）is adopted to divide the structural plane into five levels.Using the chart analysis method,selecting seven indicators of occurrence,continuity,roughness,openness,filling,spacing and groundwater status,to study the overall development of joints,and the following results are obtained:（1）Using the universal network method to measure 3407 occurrence data of structural planes,among which the steep and moderately inclined structural planes accounted for 83.06%and 16.94%of the total structural planes respectively;there are mainly three groups of dominant occurrences:330°～350°/NE,SW∠70°～85°;30°～50°/NW,SE∠80°～90°;290°～320°/SW∠75°～85°;（2）Lower structural surface continuity（Within the range of 1～3m）is the main type,about 73.4%.Followed by the very low（<1m range）continuity type,accounting for about13.9%.（3）Flatness and flatness account for the highest proportion of roughness characteristics,which is about 47.3%.（4）The type of opening degree shows a trend of"three parts of the world",that is,the proportions of the three types of medium opening,opening and closing are basically the same.（5）As a whole,the joints are the most developed with mud filling,followed by the non-filling type.（6）Most of the joints are of narrow spacing type（60～200mm）.（7）The type of jointed groundwater is reduced from dry to wet"cliff type".According to the results of tectonic stress inversion,the structure in the area has undergone three changes,namely NEE～SWW direction,NNE～SSW direction and near E～W direction,forming the characteristics of joint development in three different directions,which is basically the same as the results of previous studies.（2）Select two specific indicators,the distance between structural planes and the quality index of rock mass,RQD,and follow the results of the classification of rock mass structure types in the hydroelectric power generation survey specification,and divide the rock mass structure types of the engineering area into 5 types,namely,overall structure,blocky～sub-blocky Structure,mosaic structure,fragmented structure and bulk structure.（3）Comparing the advantages and disadvantages of the rock mass quality classification methods,two classification methods of the national standard BQ method and the"hydropower engineering geological survey specification"are selected for rock mass quality classification.The results are as follows:the two quality classification results are mainly grade III-IV,there is no grade V rock mass,and the classification results of the two methods are basically the same.In addition,according to the national standard BQ method,the rock mass quality of the upper reservoir area is divided.It is known that the overall rock mass quality of the upper reservoir area is better on the east side than on the west side.The west and north sides of the reservoir basin have relatively better integrity than the other sides.Poor,but the overall quality of rock mass is also divided into grade IV and above.（4）Using the principles of probability theory and mathematical statistics,the structural plane data obtained by the exploration of the upper reservoir is divided into homogeneous division,advantage grouping,geometric parameter probability statistical analysis and volume density estimation;using the Monte Carlo simulation principle,the three-dimensional rock structural plane is established The network model is tested and the effectiveness of the simulation method is tested,and the relative errorsεof the three-dimensional model of the rock mass structural plane are all less than 30%.It is believed that the simulation method can guarantee a certain accuracy.Visualization is achieved through the Frac Sim3D program.The window method is used to intercept a statistical window with a bandwidth of 2m,and the connectivity rate of the rock mass structural plane of the statistical window is calculated and averaged.The result shows that the average connectivity rate of the ideal cross-section of the structural plane 3D model is 39.3%.The connectivity rate is 34.8%,and the calculated results of the two connectivity rates are relatively close.