Study On Work Behavior Of Large Scale Underground Caverns Of Hydroelectric Project

With the implementation of stratagem concerning the great development of western region, a new prosperous period of hydroelectric development is coming in the rugged mountainous area of Western China, where hydroelectric resources are rich. Because of the limitation of topographical conditions, it is usually needed to lay out large scale underground caverns to develop hydroelectric resources in these areas. Under these circumstances, the underground caverns with characteristics of large scale and complex spatial arrangement are located close in finite underground space. The excavation effect and the mutual influence among different caverns related to the construction cost and operational benefit of the entire power station are the problems worthy of deep study.The FLAC software based on fast lagrangian difference method provides a new way to analyze the problems of underground structures. Because of the complexity of numerical models for underground structures and the self-shortages of FLAC software about pre/post-processing, a numerical simulation technique about underground structures is studied, using FLAC^3D software as calculation core, ANSYS software as pre-processing tool and TECPLOT software as post-processing tool. As a result, the efficiency of numerical simulation analysis and calculation is improved.The precondition for deep research on the stability of the surrounding rock is to study the mechanical properties of wall rock during the process of underground caverns excavation and supporting. Taking the underground caverns of Goupitan hydroelectric power station on Wujiang River as an example, research on the work behavior of large scale underground caverns is carried out in this paper. Three-dimensional nonlinear calculation with and without supports for the underground caverns of Goupitan hydroelectric power station is carried on, and the stability of the surrounding rock is studied by analyzing the characters of stress field, displacement field and plastic zone of surrounding rock masses after excavation and their change law during excavation. Meanwhile, by comparing with limited typical schemes of excavation and selecting the best one in those, the influence of excavation sequence on the surrounding rock stability is analyzed. The results of stable analyses for the surrounding rock of underground caverns indicate that the whole stability of the surrounding rock of underground caverns of Goupitan hydroelectric power station is relatively good.The influencing factors of the stability of surrounding rock masses are mutually associated and constrained. Using the analytic hierarchy process, the model of weight value assessment system about the surrounding rock stability of underground caverns is established preliminarily. Taking the underground cavems of Goupitan hydroelectric power station as an example and selecting 5 affecting factors on the stability of surrounding rock masses, the weight value problem of affective factors is analyzed. The method can be used in genera sequencing for influencing factors of the stability of surrounding rock masses and provide a basis for forecasting the stability of underground caverns in the future.