Construction method for jointly building underground fast road and rail traffic interval under urban main road

The invention discloses a construction method for jointly building an underground fast road and a rail traffic interval under an urban main road. The construction method comprises the following stepsthat 1, the construction of an underground continuous wall is carried out, an inclined tube is pre-buried, and cement stirring piles and anti-sinking piles are applied; 2, a soil body is excavated, supports are sequentially applied, and after the soil body is excavated to the bottom of a large foundation pit, the soil body is excavated to the bottom of a small foundation pit according to the designed slope, and a plain concrete cushion layer is poured; 3, a structural bottom plate and a side wall of the rail traffic interval are poured sequentially, the two sides of a rail cross section structure are backfilled, and a fast road frame bottom plate is poured; 4, a fourth support is disassembled, the side wall of a tunnel frame is poured upwards, and the supports are replaced; 5, a third support is disassembled, and