Seepage Analysis And Evaluation Of Seepage Control Effect In The Hewan Block Of Tuokou Hydropower Station

In the construction of large-scale water conservancy projects,it is often faced with very complex geological conditions,which cause complex leakage problems.Especially after the reservoir impoundment,the groundwater level will rise significantly,and the hydrogeological conditions will change significantly.Based on the Tuokou hydropower station on the main stream of Yuan River,the seepage parameters of Hewan block after impoundment are inversely calculated by using the stable seepage analysis method.On this basis,the seepage problems of the main dam side of Hewan block are analyzed and calculated in detail,and the seepage control effect of the anti-seepage project of Hewan block is evaluated.The main research work and results of this paper are as follows:(1)According to the data of borehole pressure water,pumping water and seepage deformation test,this paper analyzes the engineering geology and hydrogeology conditions of hewan block,makes reasonable permeability partition of hewan block rock mass,and determines the value range of corresponding permeability parameters.The results show that the permeability of hewan block rock mass can be divided into four zones:strong permeability,medium permeability,weak permeability and micro permeability.As a whole,it is dominated by weak permeability and medium permeability,and the rock mass with large permeability is basically distributed above the grouting curtain bottom line.(2)A three-dimensional finite element model is established to reflect the topography,rock mass,geological structure and impermeable structure of hewan block.Based on the monitoring data of the water level of the observation hole,the leakage amount of the gallery,the permeability division of the rock mass and the value of the permeability coefficient,the rock mass with orthogonal design and analysis with the combination of positive and inverse analysis method,the river plot run-time hydrogeological conditions to carry out the inversion analysis,to determine the suitable water boundary conditions,and check the rationality of the value of rock mass permeability partition and permeability coefficient The inversion results show that the calculated value of the head at the observation hole is in good agreement with the measured value,and the calculated value of corridor leakage is also in good agreement with the measured value under each inversion condition.The average absolute error of the head is 1～3m,so the inversion results are relatively reliable.(3)Based on the results of the seepage parameter inversion analysis of hewan block,the three-dimensional seepage finite element analysis of hewan block is carried out by using the method of steady seepage analysis,and the seepage problem of the main dam side of hewan block is deeply studied.The research shows that the underground water level in the mountain of Hewan massif falls in a funnel shape above the gallery,and the leakage at the main dam side of Hewan massif is relatively large.The main source of the leakage is that the internal mountain is connected with the reservoir area through some rocks or faults with high permeability and strong water conductivity,which leads to the high underground water level of the internal mountain and the phenomenon that the gallery is flooded by seepage.The main dam side of hewan block has strong permeability in the areas of irrigation 300-500,600-700 and 800-881.Under the condition of water level of 241m and 248.7m,the leakage amount of the side corridor of the main dam is 1580.57m3/d and 3432.24m3/d,respectively.The water level of the main dam has a significant influence on the leakage amount of the side corridor of the main dam.(4)Based on the curtain arrangement scheme of the impermeable section of hewan block,the rationality of the impermeable scheme of the main dam side of hewan block is reviewed,and the seepage control effect of the impermeable project of hewan block is comprehensively evaluated with the results of three-dimensional seepage analysis of hewan block.The impermeable scheme of hewan block is reasonable on the whole.Except for the large slope of corridor lining,the seepage slope of other parts is relatively small,which generally meets the permeability stability requirements.(5)In view ofthe flooding phenomenon of the main dam side corridor in hewan block,the paper puts forward corresponding Suggestions on seepage drainage,seepage prevention and monitoring measures,and comprehensively analyzes the structural stability of grouting corridor lining during seepage drainage.The analysis results show that the compressive stress and tensile stress of lining are within the allowable range,and the corridor structure is basically in a stable state.It is suggested to carry out the seepage drainage work in the corridor under the condition of low reservoir water level.If the drainage work is carried out under the condition of high reservoir water level,attention should be paid to the seepage stability of the corridor and surrounding rock mass.