Displacement Back Analysis Of Wudongde Underground Powerhouse Cavern Groups During Construction Period

The western region in China has concentrated hydropower resource. As an important hydraulic structure, underground powerhouse often constructs in complicated geological condition, which is so complex that existing technical standard and experience knowledge has been unable to meet the demand of the construction of large underground cavern groups. The stability of surrounding rock of underground cavities design has become a research focus. Oriented to the needs of the current major hydropower project construction, this paper carried out the study of optimization design method of surrounding rock stability during the construction of large underground powerhouse cavern groups. This paper establishes a back analysis system. The system has three key technologys, including the initial geostress inversion, monitoring data analysis and the identification for stability of surrounding rock, as well as parameter inversion.To sum up, this paper’s main research work carried out as follows:(1) This paper Absorbs the advantage of the existing underground engineering optimization feedback method, integrate the theory and technology of displacement back analysis method and numerical method, supporting technology, monitoring technology of surrounding rock, the initial geostress inversion method, engineering optimization, etc. Combine with the characteristics of the underground powerhouse cavern groups, the paper establish displacement back analysis system of during the construction of large underground powerhouse cavern groups.(2) The inversion method of initial geostress are analyzed and compared. Use regression analysis method to the inverse the initial geostress. Generalize three-dimensional geological model of the right bank underground factories in Wuongde Hydropower. The data of practical exploration is used to inverse initial geostress.The inversion results show that the regional stress is given priority to with gravity stress, and the distribution characteristics of geostress near the bank of river valley correspond to which in river valley region.(3) Comprehensive analysis carry out the revealed geological data and safety monitoring data in Wuongde Hydropower during the construction of the right bank underground powerhouse. Two important relationships were focused research. One relatonship is between the displacement of surrounding rock and space effect, and the other is between the displacement of surrounding rock and the geological condition. Analyse the surrounding rock deformation distribution characteristics of three caverns of underground powerhouse. The paper Analyze and evaluate about the role of support measures to control the displacement of surrounding rock.(4) This paper Analyzes and compares the monitoring data and geological conditions of every cross section. Choose the reasonable inversion section. Surrounding rock parameters of underground powerhouse of two-dimensional finite element model is established. For reasonable selection for inversion parameters of surrounding rock, on the basis of using single parameter sensitivity analysis, study using orthogonal design method to analyse mult-parameter sensitivity. High sensitivity of parameters of surrounding rock are obtained. The results show that two sensitivity analysis methods validate with each other, and obtain similar conclusions.(5) The neural network inverse analysis method based on orthogonal experimental design are studied to inverse parameters of surrounding rock every layer. In order to test the inversion effect, using measured data and prediction data to evaluate the efficacy of the inversion method, and achieve the goal of optimization inversion.