| The regional geological conditions of Wudongde Hydropower Station underground powerhouse on the left bank of Jinsha River are complex. The scale of main underground powerhouseis very large, and the excavation height of the main building is at the highest level of the same kind of projects and cavern span and high side wall cavities arranged in a crisscross pattern.The stability of surrounding rock of main underground powerhouse can be adversely affected by the excavation unloading.In view of this,based on lots of engineering geological investigation data and the measured in-situ stress data,this paper established a three-dimensional geo-mechanical model to conduct the initial stress field regression analysis so as to obtain the initial stress field in dam area.The results obtained from the regression analysis are applied to the calculation model to simulate the initial in-situ stress field. This paper simulated the excavation process of main underground powerhousein the left bank and obtained the stress field, displacement field and plastic failure zone of surrounding rock under the condition of tunnel excavation and assess the surrounding rock stability after excavation. According to the analysis and calculation results, combining with the related specifications and taking an analogy with other underground powerhouse supporting measures, this paper puts forward some suggestions of supporting measures for the main underground powerhouse of the excavationof Wudongde Hydropower Station, The simulation was conducted after the support according to the proposed support suggestion, the calculation results of two kinds of working conditions are compared, the effectiveness of the support function and the influence on the stability of surrounding rock are explained.The following research work is carried out around the above objectives:(1) A site geological survey of Wudongde hydropower station dam was conducted to identify the dam site topography, lithology, geological structure and other basic geological conditionsin order to lay the foundation for the establishment of a reasonable calculation model.(2) Field investigation of in-situ stress measuring points within the scope of the study was conducted,and the spatial position, orientation and the formation lithology of the stress measuring points in each place were defined.The in-situ stress measuring data were collected and analyzed in order to comprehendthe stress conditionsof the left bank dam area.(3) This paper established a reasonable three-dimensional geo-mechanical model of underground cavern on the left bank of dam area within the scope of the study. Multiple linear regression analysisof initial in-situ stress field of the left bank dam area was carried outing order to get the distribution of initial stress field of the dam area and lay the foundation for the subsequent excavation simulation of themain underground powerhouse.(4) The results obtained from the regression analysis are applied to the calculation model to simulate the initial in-situ stress field. This paper simulated the excavation process of main underground powerhousein the left bank and obtainedthe stress field, displacement field and plastic failure zone of surrounding rock under the condition of tunnel excavation. At last, the stability of surrounding rockwereanalyzed and evaluated.(5) According to the result of numerical simulation, combining with the related specifications and taking an analogy with other underground powerhouse supporting measures, this paper puts forward some suggestions of supporting measures for the main underground powerhouse of the excavation of Wudongde Hydropower Station.(6) The simulation was conducted after the support according to the proposed support suggestion,by comparing the stress field, displacement field and plastic failure zone of two kinds of working conditions, the effectiveness of the support function and the influence on the stability of surrounding rock were explained. |
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