METHOD OF PRE-SUPPORTED TUNNEL COSTRUCTED IN A SOFT GROUND

摘要

The present invention relates to a method of constructing a pre-supported tunnel installed in soft grounds for designing and building a tunnel in soft grounds where soil is shallow in an entrance and an exit of the tunnel and a downtown tunnel. According to the present invention, a method of constructing a pre-supported tunnel installed in soft grounds comprises: a step for installing multiple pre-supported materials designed for penetrating a pre-supported material into an outside of right and left to the longitudinal direction of a tunnel plan cross section, and into the depth required for the bottom of the tunnel from the top of the ground to the transverse direction for cutting off or supporting the pre-supported material before a tunnel is excavated in a ground surface; a step for excavating a pre-supported tunnel plan cross section; a step for removing the pre-supported material by cutting the pre-supported material in the length necessary for installing a bearing plate after installing a shotcrete and a steel rib; and a step for re-attaching the shotcrete for coating after installing the bearing plate. A traverse arch and a longitudinal arching are secured while being excavated at the same time according to a pre-supported material which is pre-constructed before excavation. Since the pre-supported material is installed from the ground surface to a lower part of the bottom of the tunnel as a column, the ground of an upper part of the tunnel is supported as a column, and a working face is stabilized and the ground of a lower part is cut off. The tunnel is excavated more securely without an unsupported state generated in excavation to a traditional NATM. Since relaxation of the foundation can be minimized, a reduction amount of ground strength of the foundation is decreased.