A SYSTEMIC EVALUATION OF SEEPAGE STABILITY FOR FRACTURE ZONE IN LUHUN DAM FOUNDATION

Luhun Reservoir lies in the middle reaches of Yi River, Songxian County, Luoyang City, Henan Province, China. The authors have analyzed the water-level observation references for the past over 30 years, and determined the qualitative analysis of the hydrogeological models. On this basis, this paper presents, in line with the principle of modern mathematical statistics, a successful solution to the seepage in the dam foundation that has prevented the normal operation of the reservoir. This solution deepens our understanding of the seepage stability and its changing pattern for the dam foundation, in order to secure the normal operation of the dam when the reservoir reaches its normal high water levels (319.5 m, 327.5 m, 331.8 m).The research results show that the present operation of the dam is normal, that the weak parts of the cut-off trench can be consolidated during the slow storage of water in the reservoir, and that the seepage resistance rate at the interface between the soil fill and the rocks in the cut-off trench may reach over 45. The seepage-proof system consisting of the blanket in the upper reaches and the cut-off trench combined with the drainage in the lower reaches has effectively controlled the seepage in the dam foundation. At the same time, the seepage in the dam foundation when the water level is high is forecasted to be stable, so that the reservoir can be put to operation when the water level in the reservoir is high, providing an example of the proof of a defective and dangerous reservoir.