Seepage field analysis and evaluation of seepage control effect at the dam foundation of Baihetan Hydropower Station

摘要

With a large catchment area, stratified groundwater on the left and right bank, developed unloading fissures in the damfoundation rock, and prominent permeability anisotropy in columnar jointed basalt, the dam site of Baihetan HydropowerStation possesses complex seepage control measures. Moreover, the water head difference between the upstream and downstreamcan reach 235 m after impoundment, and thus, the seepage field of the dam site area will be extremely intricate. Inthis study, we analyzed the seepage field characteristics of the dam foundation during impoundment with field measurementdata, and conducted numerical simulation of seepage field under normal water level condition with steady seepagecalculation method. With the field measurement data and the numerical simulation results, we evaluated the performanceof the seepage control system and revealed the movement process of the seepage flow in the dam foundation. The analysisresults show that the impervious curtain can effectively stop the reservoir water from flowing to downstream side of thedam through the rock masses in the dam foundation, the drainage holes of the dam foundation can successfully mitigate theuplift pressure, and thus, the stability of the dam body has been guaranteed by the current seepage control system. Besides,driven by high water head difference, the reservoir water penetrates downstream through the deficient area of the impermeablecurtain and flows along the micro-cracks developed in rock layers P_2β_3~(2?2) and P_2β_3~(2?1), then discharges through thedrainage holes in the dam foundation.