Regression Analysis Of Initial Geostress Field For Dam Site Area Of Shuang Jiang Kou Water Power Stationd

In the 21st century,with the rapid development of water conservancy and hydropower projects,a large number of large-scale hydropower projects have entered the construction period since the western development,and some large underground caverns are under planning and design.These projects,such as the Three Gorges hydropower project,Jinping I and II hydropower projects,Xiaowan hydropower project,etc.,are in the leading position in the world in terms of the number and scale of the cavern group and the diversion tunnel group.The construction of the underground cavern group of hydropower projects gradually presents the following two characteristics:first,the depth of the cavern is large,second,the geostress level is high,and the maximum principal stress of the Shuangjiangkou Hydropower Station is close to 40MPa.The initial in-situ stress field is a key factor to be considered in the process of underground engineering construction,which is affected by many factors.It is impossible to obtain a large number of measured in-situ stress results in the actual engineering construction.Therefore,how to obtain the initial in-situ stress field in the engineering area through the inversion method based on some measured points is of great significance for the underground engineering construction.Firstly,this paper studies the development process of in-situ stress inversion analysis method and some main inversion methods in the current stage.On the basis of comparative analysis and reasonable inheritance of previous research results,the dam site area of Shuangjiangkou Hydropower Station is analyzed by the combination of finite difference numerical calculation and multiple regression analysis.The main work and achievements of this paper are as follows:?1?This paper introduces the general situation of Shuangjiangkou Hydropower Station project and the relevant of engineering geological conditions in the dam site area.On the basis of summarizing and sorting out the data information of some measured points in the dam site area,a preliminary analysis of the distribution characteristics of the in-situ stress in the dam site area is carried out by means of experience and mathematical statistics analysis,and the distribution law of the direction and value of the in-situ stress in the dam site area is obtained through analysis.?2?This paper systematically introduces the principle and method of multiple regression numerical calculation used in this inversion analysis.Considering the effect of self weight stress and tectonic stress,the influencing factors of inversion are determined.This paper introduces the realization method of boundary condition in numerical calculation,the methods of the multivariate regression analysis and subsequent data test.?3?After determining the calculation range,we use MIDAS/GTS to establish a three-dimensional geological generalization model.After the mesh is divided,it is imported into FLAC^3D,and the selection and transformation of measuring points,boundary constraints and other work are carried out.According to the determined six basic working conditions,the geological model is calculated numerically,and coefficient regression is carried out based on the least square method,and the regression coefficient of each working condition boundary condition is obtained.?4?The significance test of the inversion results is carried out.After the data test,the regression coefficient is multiplied by the boundary conditions and then added on the model for calculation.Finally,the initial geostress field of the calculation area and the analysis results are obtained.By comparing the calculated value of regression with the measured value,it is found that the regression results are in line with the reality.On this basis,through the study of the main stress nephogram,combined with the analysis of the actual situation of the site,and the basic distribution law of the initial geostress field in the dam site area is obtained based on the analysis of the actual situation of the site,which plays a guiding role in the engineering construction...