Study On Seepage Analysis And Optimization Of Treatment Measures In Dam Site Of Qianping Reservoir

The seepage problem in the dam site will not only affect the normal performance of reservoir benefit,but also affect the safety and stability of dam body greatly.Qianping Reservoir is located in the upper reaches of North Ruhe River,a tributary of Shaying River in Huaihe River Basin,and near Qianping Village,9 km west of Ruyang County,Luoyang City,Henan Province.The total storage capacity of the reservoir is 590 million m~3,and the main dam is composed of clay core wall sand,egg(gravel)rockfill dam,the maximum dam height is 90.70 m.It is considered that there is a leakage channel in the dam area of the reservoir,and a large amount of leakage is possible.Based on the detailed analysis of engineering geological conditions,hydrogeological conditions,dam abutments and seepage control systems in the dam site area of Qianping Reservoir,this paper makes a thorough calculation and analysis of the original anti-seepage treatment measures in the dam site area by using three-dimensional finite element numerical calculation and analysis method.On this basis,the seepage treatment measures are optimized.The main contents are as follows:(1)The possible leakage problems in the dam site of Qianping Reservoir are analyzed and evaluated,and the spatial distribution characteristics of F2 fault and F6fault are analyzed by magnetotelluric method.The results show that there is spatial distribution of F2 fault and F6 fault in the lower reaches of the dam.There is a possibility of intersection downstream of the dam.The analysis shows that leakage around the dam exists in the area of Qianping Reservoir.(2)Based on the finite difference method,the natural seepage field of the dam site area of the Qian Ping reservoir is analyzed,and the distribution characteristics of the initial groundwater in the dam site of the Qian Ping reservoir are mastered.The analysis shows that the distribution of natural seepage field is obviously affected by river flow direction and mountain watershed,and the variation is small.(3)In view of the leakage problem in the dam site caused by the completion of Qianping Reservoir,a three-dimensional finite element model is established by using the finite element method.The width and ductility of the fault zone,the thickness of the overburden and the weathering of the bedrock are reasonably generalized.The seepage problem in dam site of Qianping Reservoir is analyzed.(4)Based on the original design of seepage control scheme,the seepage control measures in the dam site of Qianping Reservoir are optimized and the best seepage prevention scheme is recommended.The elevation of the dam foundation impervious curtain bottom plate was raised from 261m to 290m.The total leakage of the dam site area was reduced from 4220m~3/d to 4220m~3/d,and the seepage curtain reduced the total leakage amount to 99.13%,and the annual leakage amount was 0.46%of 332million m ~3 of the annual runoff.The hydraulic gradient of F2 fault is reduced from5.46 to the maximum value of 1.71 under the condition of no seepage control.The hydraulic gradient will not occur seepage damage within the allowable range of the project.After the optimization of impervious measures,the depth of curtain grouting is reduced,the project investment is saved,the construction period is shortened,and the economic and social benefits are remarkable.