CONSTRUCTION METHOD OF SMALL DIAMETER TUNNEL

PROBLEM TO BE SOLVED: To improve the execution by delivering a hole wall protecting sheet in a cylindrical shape from a leading body to perform the excavation with water jet, and discharging the hardening agent outside the sheet. SOLUTION: A leading body 1 is connected to the tip of a flexible multi- layered tube 2 comprising a high-pressure water pipe 14, a hardening agent pipe 15 and an earth sand discharge pipe 11. In the execution, the high-pressure water from the pipe 14 is jetted from a jet port 4 to cut the ground, and the cut earth and sand is fed backward by the discharge pipe 11 through an earth and sand inlet 16. The leading body 1 performs the excavation with the discharge pressure of the jet water from a discharge nozzle 12 and through the rotation by a driving device 6, and its direction is corrected by correcting the opening angle of an attitude control fin 13. A hole wall protecting sheet 9 is delivered backward from a delivery port 10, the hardening agent 8 is poured outside from a pouring port 7, and hardened to form the hole wall. Execution can be achieved without any large starting shaft or buried tubes, the gravel bed or hard pan can be coped with, and a curve can be executed.