SMALL-BORE SHAFT STARTING TYPE PIPE-JACKING METHOD FOR JACKING-PIPE BY SEMI-SHIELD MACHINE

PROBLEM TO BE SOLVED: To carry out starting from a limited work site and improve work efficiency while reducing term of works for pipe-jacking method wherewith jacking pipes are laid in the ground by a semi-shield machine, starting from a starting shaft, by a method wherein the pipe jacking from a small-bore starting shaft is made practicable by utilizing a large-bore temporary-laying pipe laid beforehand. SOLUTION: A leader excavator 3 equipped with a propulsion jack 3C made up by putting a temporary-laying pipe 3B onto a semi-shield machine 3A is housed in a small-bore starting shaft 1, and the leader excavator 3 is pushed forward and laid in the ground, starting from a circumferential through hole 1b of the starting shaft 1, by operation of the propulsion jack 3C while a cutting face B is excavated with a diametrally expanded rotary expansile cutter 3a of the semi-shield machine 3A. Then, the propulsion jack 3C is removed, and the semi-shield machine 3A is pushed forward for excavation, with its diameter being contracted, from the temporary laying pipe 3B by operation of a primary jacking device 4 installed at the starting shaft 1. A jacking pipe 2 is hung down and turned and connected to the semi- shield machine 3A with its opening 2a at one end brought into the large-bore temporary laying pipe 3B, and the jacking pipes 2 are successively pushed forward and laid, being pressed by the primary jacking device 4, while the semi-shield machine is operated.