Trail section additional strength manner of the tunnel which

摘要

PROBLEM TO BE SOLVED: To effectively prevent the settlement or deformation of timbering when excavating an upper half cross section of a mountainous tunnel. SOLUTION: A leg portion 16 of a steel timbering 15 with wing ribs built during the excavation of an upper half cross section 1A of the tunnel is placed on the beam-receiving pipes 10. Prior to the excavation of the upper half cross section 1A of the tunnel, a beam receiving pipe 10 is embedded in a direction parallel to the longitudinal direction of the tunnel by using a drive excavator 3 on the natural ground 2 below a leg portion 16 of the steel timbering work 15 with wing ribs supporting the upper half cross section 1A of the tunnel.