High-flow and high-head antiscour and anti-seepage overflow cofferdam structure and construction method thereof

The invention discloses a high-flow and high-head antiscour and anti-seepage overflow cofferdam structure and a construction method of the structure. The structure comprises a CSG (Constructive Solid Geometry) cofferdam located on excavated riverbed bedrock and taking a riverbed excavation material as a major material source, wherein an anti-seepage surface layer of a cofferdam body is arranged on the upstream surface of the CSG cofferdam; a cofferdam foundation anti-seepage curtain is arranged at an upstream cofferdam toe of the CSG cofferdam; an anti-seepage layer of the downstream cofferdam body of the cofferdam is arranged on the downstream surface of the CSG cofferdam; a precast concrete block is arranged on the surface of the anti-seepage layer of the downstream cofferdam body of the cofferdam; and a normal concrete protection cover is arranged on the top of the CSG cofferdam. The anti-seepage surface layer of the upstream cofferdam body of the cofferdam and the anti-seepage layer of the downstream cofferdam body of the cofferdam are made of a material by adding cement paste into the material of the CSG cofferdam to improve anti-seepage capability. The cofferdam structure is simple in overall layout, achieves use of local materials, utilizes waste materials, simplifies a technology, and is an environment-friendly project. The cofferdam structure achieves scour prevention, seepage prevention, environmental protection and the like of the high-flow and high-head overflow CSG cofferdam, greatly reduces work amount and saves project investment.