Method of constructing secondary tunnel tunnel and branch shield used in the method of construction

摘要

PROBLEM TO BE SOLVED: To provide a construction method for a subordinate tunnel pit that can collect a branch shield even when a sufficient collection space cannot be secured at an arrival position or when there is an existing structure obstructing collecting operation in front of the branch shield, and a branch shield used by the construction method.SOLUTION: A branch shield 1 comprises an inner shell 7 provided with a cutter 5 and a drive part 6 therefor provided on one body, and an outer shell 8 accommodating the inner shell 7 and formed to be divided in a peripheral direction. After the branch shield 1 reaches a target arrival part, the inner shell 7 is taken out of the outer shell 8, and collected in a main tunnel pit 2 through the outer shell 8 and a structured subordinate tunnel pit 4, and then the outer shell 8 is divided in a peripheral direction into divided outer shells 8, which are collected in the main tunnel pit 2 through the structured subordinate tunnel pit 4.SELECTED DRAWING: Figure 1