Abstract: Water shortage in the karst areas of southwest China is expected to be solved by building reservoirs to store water.However,the widespread development of karst funnels and sinkholes in this area will cause the leakage of water storage in the reservoir and finally result in the failure of water conservancy projects.Grouting curtain is an effective means to reduce the permeability of rock in the reservoir area.The key to accomplish the project with low cost and high quality is to optimize the grouting curtain process and its parameters.In this research,the mix proportion of grouting material,the spacing between boreholes,the grouting pressure,the bottom boundary of curtain,and the grouting techniques were optimized by combining laboratory experiment,numerical simulation,and field test.Results demonstrated that the permeability of grouting curtain system in Dehou reservoir area can be controlled less than 5 Lu if the following conditions are met:water-cement ratio is controlled between 1∶1-1∶3,the boreholes are arranged in a single row with the hole spacing at 2.0 m,the grouting pressure is 1-2 MPa,the control depth of the curtain's bottom boundary is 10 m below the depth of the weathering layer,the grouting is carried out in segments,and the length of the first,second and subsequent segments are 2 m,3 m and 5 m,respectively.The research findings offer theoretical and experimental support for the optimization of grouting curtain parameters in Dehou reservoir area,and also provide reference for similar projects in karst area in southwest China.

Key words: karst reservoir area, grouting curtain, parameter optimization, water injection test, seepage control, mix proportion