Composite seepage preventing structure for large karst cave in karst region and construction method thereof

The invention discloses a composite seepage preventing structure for a large karst cave in a karst region and a construction method thereof, and belongs to the technical field of water conservancy and hydropower engineering. The composite seepage preventing structure comprises bed rock and the karst cave. The karst cave is located in the bed rock. The lower section of the karst cave is filled to form a karst filling area. A plurality of filling-material rotary jetting holes or steel pipe piles are vertically distributed in the karst cave filling area and arranged along the seepage preventing axis at intervals in a rowed mode. A transition cushion layer is arranged on the upper surface of the karst cave filling area. A concrete seepage preventing wall is arranged on the steel pipe piles. A cavity in the upstream side of the concrete seepage preventing wall is backfilled to form a backfilling area. According to the technical scheme, due to the reasonable construction method, the concrete seepage preventing wall is built in the karst cave, and the quite good partition effect and the quite good sealing effect are achieved through a karst cave roof joining groove structure in the top and a grouting-cave-aligning-grouting method; the structure and the method are simple, the quantity of input materials is small, construction intensity is small, construction efficiency is greatly improved, and the seepage preventing aim of large karst cave in the karst region is achieved.