CONSTRUCTION METHOD OF MEDDLE WALL OF THREE ARCH EXCAVATION TUNNEL

摘要

A construction method for a middle wall of a 3-arch type tunnel is provided to shorten a period of tunnel excavation and to cut down construction expenses as a whole with the effective use of tunnel equipment. A construction method for a middle wall of a 3-arch type tunnel comprises the steps of blasting a pilot tunnel for the middle wall construction and placing shotcrete and rock bolts on the pilot tunnel, installing a perforation standard frame in the pilot tunnel, pre-perforating charge holes radially toward main tunnels on the right and left sides of the pilot tunnel, constructing a middle wall on the inside of the pilot tunnel, perforating a charge hole on the excavation borderline of the right main tunnel in the longitudinal direction of a tunnel and blasting, excavating a charge hole on the excavation line of the left main tunnel in the longitudinal direction of a tunnel and blasting, and installing rock bolts radially on the arch line of the left main tunnel. Hereon an intercepting drainage basin(70) is installed on the end of a drain board to make the water guided to the drain board gathered and drained off smoothly. An installation method of the intercepting drainage basin comprises the steps of coupling the intercepting drainage basin to reinforcing bars longitudinally by regulating the gradient and level of drainage, placing primary concrete to the middle of the intercepting drainage basin, installing a mold on the upper part of the intercepting drainage basin and placing secondary concrete, stripping off the mold and cutting out the upper part of the intercepting drainage basin, inserting the drain board into the intercepting drainage basin of the pillar portion and waterproofing a gap between the intercepting drainage basin and the drain board, and then placing lining concrete.