| 摘要 |
PROBLEM TO BE SOLVED: To obtain cut-off effect even when a plurality of tunnel linings are formed at one start port.SOLUTION: There is provided an entrance structure for a tunnel which includes a plurality of tunnel linings 20, 20 arranged side by side at an interval, an outside entrance 30, and an inside entrance 50. The outside entrance 30 includes first cutoff means 31 coming into contact with an outer peripheral surface of the inside entrance 50, which includes a plurality of ring parts 51, 51 provided corresponding to the plurality of tunnel linings 20, 20, a connection part 52 closing a gap between the adjacent ring parts 51, 51, and a plurality of pieces of second cutoff means 55 provided for the plurality of ring parts 51, 51 respectively. The respective ring parts 51 surround the respective tunnel linings 20, and the second cutoff means 55 comes into contact with an outer peripheral surface of each tunnel lining 20, and is adjustable in frictional force against outer peripheral surfaces of the tunnel linings 20, 20. |
