| 摘要 |
PROBLEM TO BE SOLVED: To provide a tunnel excavation method capable of reducing the amount of outbreak of a tunnel to reduce an amount of use of concrete.SOLUTION: In a tunnel excavation method, a plurality of blastholes 2 are drilled in a working face 1 of a natural ground, and thereafter the blastholes are loaded with explosives and blasted to excavate a tunnel 3. Next, rock bolts are driven into the natural ground from the surface of the tunnel and concrete is sprayed onto the surface to form a primary lining 7. Then, concrete is arranged on the surface of the primary lining to form a secondary lining 8, and thereby, when forming the tunnel, a drilling starting point a in the working face of the blastholes obliquely formed in the outer peripheral part and outside of the tunnel is located on more inner peripheral side than a planned excavation line PL while a drilling end point b is located on more outer peripheral side than the planned excavation line. Then, after further drilling and blasting, a pointed end part 4a on more inner side than the planned excavation line of a pointed part 4 remained in a saw blade-shape on the inner wall surface of the tunnel is removed by an electric discharge crusher. |
