Large-arch-foot three-step tunnel rapid construction method and structure based on pipe shed pre-supports

The invention discloses a large-arch-foot three-step tunnel rapid construction method and structure based on pipe shed pre-supports. Short pipe sheds are constructed through a hole interior non-work-room pipe shed construction technology to reinforce and support surrounding rock in front of a tunnel face in advance; large arch feet are arranged at bases all stages of steps; and under dual controlmeasures, the tunnel cross section is sequentially excavated by three steps, according to the specific processes, firstly, short pipe shed advance supports are constructed within a certain range alongan arch part of a tunnel, the upper, middle and lower steps are sequentially excavated with alternate distances, after excavation of each step, the primary supports are constructed instantly, footings of the primary supports are designed to of a large-arch-foot type, and when the lower step is away from a secondary lining of a former cycle by the tunnel diameter, an inverted arch, side walls, a filled layer and a secondar