SPATIAL PREDICTION METHOD OF ROCK MASS DETERIORATION IN DRAWDOWN ZONE BASED ON SEEPAGE DIFFERENCE OF FRACTURE NETWORK

Since the impoundment of the Three Gorges Reservoir at 175 m,the water level has periodically fluctuated,causing the strength of the bank slope to decrease and gradually deteriorate,which easily leads to instability and destruction of the rocky bank slope. So it has attracted widespread attention. The deterioration of the rock mass is related to the fluctuation of the reservoir water level,and the area of damage and deterioration must have a certain relationship with the scope of hydraulic adjustment. This paper presents for the first time a spatial analysis method of rock mass degradation based on the seepage difference of the fracture network model. The Beacher model is used to simulate the spatial distribution of rock mass fractures in combination with the fracture geometric parameter distribution probabilistic model. Based on the equal cross-sectional area of the fractures,the surface seepage in the fracture network is simplified as a pipeline flow,and the seepage space diagram of the fracture network is constructed. At the same time,the topological relationship is used to solve the water head distribution area in the seepage space of the rock mass fracture network in the actual working condition. The space where the rock mass degradation may occur through the seepage difference area under different water levels is used to obtain the new seepage area with the same hydraulic difference and the new water level change. Based on theoretical analysis and numerical simulation,it is concluded that the area with hydraulic difference and the newly added seepage area are the area of rock mass deterioration. This prediction method can have important guiding significance for quantifying the spatial strength of rock mass deterioration and bank slope stability in the Three Gorges Reservoir area.