Study On The Engineering Geological Property Of Deep Overburden In The Danba Hydroelectric Power Station, Dadu River

By 2006, the theories reserves of water power resources are 6.19×10¹² kWH in China, and it is more than 80 percent of the country's in the west of China. So this region has immense hydropower development potential. However, the riverbeds of this region's rivers are the deep overburden whose thickness is general more than 30m. The engineering geology evaluation of those deep overburden has become a problem in the hydropower development process.The proposed Danba hydropower station located in Danba County of Ganzi Tibetan Autonomous Prefecture, Sichuan Province, is the eighth hydropower station in the Dadu river hydropower development plan. Its dam height is 116m, and its installed capacity is 1.56×10⁶kW. The engineering geology condition, composition, structure and origin of the overburden whose the most thichness is more than 100m are quite complex in the dam site. The physical properties, mechanical properties and engineering geological character of the overburden's each parts are great different. It should be noted that there are three sand layers that are iacustrine sediments and large number of sand lens whose thichness is different. So the problem of dam stability is especially prominent.Based on those data of exploration, in-situ tests and laboratory tests, the spatial distribution and the engineering geological property of the overburden will be analyzed in the Shuikazi dam site. The allowable bearing capacity, the settlement of ground, the seepage field and the liquefaction of sand will be analyzed too.The analysis result indicated that the anti-slide stability of the dam meets the project needs. The seepage analysis result indicated that some seepage control measures should be used to decrease the leakage. The settlement calculation result and the finite element analysis result indicated that the maximum settlement value of the overburden meets the project needs. If aâ…¦earthquake takes place in the dam site, the sand of theâ‘¢layer, theâ‘£layer and the⑤layer will take place liquefaction. Finally, theâ‘£-2 layer is considered as bearing stratum, and the elevation of the dam foundation is 1940m.A finite element model is built to simulate the seepage field of the overburden that is done curtain grouting, and the simulation result indicated that the curtain grouting can effectively decrease the leakage. The ground treatment option that are the dynamic consolidation replacement option that is use to treat the depth shallow sand and the grouting option that is use to treat the depth deep sand will be done.