Pre-reinforcement system for overpass planned tunnel line of open cut tunnel foundation pit and construction method

According to the open cut tunnel foundation pit overpass planned tunnel line pre-reinforcement system and the construction method, in the construction process, firstly, three-shaft mixing pile blades are used for conducting hard soil layer variable-diameter mixing, and then a profile steel guiding and positioning technology is used for vertically inserting profile steel into the piles to form the three-shaft mixing piles; then, a guide groove is excavated through a hydraulic grab bucket and a hydraulic double-wheel slot milling machine, a glass fiber rib reinforcement cage is put down, main ribs and glass fiber ribs are connected through U-shaped buckles, longitudinal truss ribs and transverse truss ribs are installed for reinforcement, and an underground diaphragm wall is formed; and finally, jet grouting the consolidated body to form a jet grouting pile. The foundation bearing capacity is effectively improved, uneven deformation is reduced, the potential influence of planned tunnel construction on a built t