Deep foundation pit supporting structure under karst geological condition and construction method thereof

The invention provides a deep foundation pit supporting structure under the karst geological condition and a construction method thereof. The supporting structure comprises a closed annular retainingwall built along a foundation pit wall surface, and a plurality of telescopic support bars arranged horizontally in an area enclosed by the closed annular retaining wall; and all the telescopic support bars are parallel to each other. The construction method comprises the steps that a foundation pit is excavated, the retaining wall is built along the side wall of the foundation pit, and the plurality of telescopic support bars are mounted and locked on the two opposite side wall surfaces of the retaining wall. By adopting the technical scheme, water leakage of the foundation pit side wall is effectively prevented through the closed annular retaining wall, the telescopic support bar supporting structures are simple and easy to use and convenient to disassemble and assemble, and can be locked at any time, the streng