Excavation supporting system for barrier lake discharge tunnel

The utility model provides an excavation supporting system for a barrier lake discharge tunnel. The drainage tunnel comprises a pipe shed, tunnel steel bodies and open caissons, and is characterized in that the drainage tunnel is provided with one or more open caissons and multiple sections of independent tunnel steel bodies, the cross section of each tunnel steel body is in a lower frame shape and comprises a supporting plate and a supporting frame, and each supporting frame is of a telescopic structure capable of being fixed in the vertical direction; the horizontal section of the open caisson comprises a rectangle, a circle or an ellipse; foot with blade at bottom, movable wall plates are arranged in the single-side direction and/or the double-side direction of the bottoms of the two sides of the open caisson. The movable wall plate is of a single-block or multi-block combined structure, a tunnel excavation opening is formed after the movable wall plate is disassembled, the tunnel steel body is installed a