Urban open cut underneath pass tunnel excavation supporting system and construction method

The invention provides an urban open cut underneath pass tunnel excavation supporting system and a construction method. A shaped shortcut which is provided with anti-skid rib plates and can be splicedrapidly is adopted, so that the driving safety and speed are improved, the instability possibility of a foundation pit is reduced, and the construction speed is increased; construction is carried outby adopting a slope reinforcing mesh rapid binding jig frame and a slope supporting shaping movable operation platform, jig frame side plates of the slope reinforcing mesh rapid binding jig frame arefixed by installing side plate fixing pieces on the inner side and the outer side, the reinforcing bar binding speed is increased, slope stabilization is facilitated, and operation of constructors isfacilitated; through the prefabricated assembly type tower crane foundation technology, a prefabricated center component of a prefabricated assembly type tower crane foundation is placed in the center of a cushion layer, and pr