| Taking the rock stability after excavation of Nuozhadu Hydropower station as research target, the 3-D elastic-plastic finite element analysis method as research measure, this paper analyzes and appraises the rock stability of different excavation sequence and of different support program. Main contents include the following.First of all, this paper generalizes the developing process and present situation about caverns excavation at home and abroad, and then makes an induction of three problems about theoretical foundation involved in cavern excavating. The three problems include initial stress fields fitting, selection of constitutive model and stability analysis of surrounding rock. Then according to the engineering background and geological conditions of this workshop, select a theory foundation.In chapter 4, first give a regression analysis for initial stress fields in calculation range; establish 3-D finite element model, and then determine the calculation range, material parameters and boundary condition. Next process the 3-D fern simulation about the excavation without brace, then analyses the results of stress and strain. At last process the 3-D fern simulation the excavation with brace, and compare the results with the excavation without brace.In chapter 5, first simulate the process of excavation with brace from different section under three working conditions. Then analyze the stability of surrounding rock and anchorage parameters, and optimum excavation order by comparing the stress of surrounding rock and anchor rod under different working condition.In the end, this paper concludes the stability of surrounding rock excavation with and without brace from different section, gives optimal excavation scheme based on simulation results, and then gives suggestions about related problems in construction process. The related conclusion can be used as a reference for similar engineering design in the future.
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