TUNNEL CONSTRUCTION METHOD AND SHIELD DEVICE USED THEREFOR

PURPOSE:To construct a tunnel of large and flat cross section with high workability and economically. CONSTITUTION:Pilot tunnels 3b and 3b are drilled in advance and side wall concretes 33 and 33 are placed therein. A shield device 5 having a front end 6a sloping in such state as set back from the top end of a hull 6 to right and left lower sections is installed and supported on the concretes 33 and 33 via support shoes 10 and 10 formed on right and left lower sections. Then, the shield device 5 is placed in front of a tunnel face 2a in such state as placed in each pilot tunnel 3b. Thereafter, the tunnel face 2a is excavated, while a foot 7 being projected to support a tunnel wall, with the device 5 inclined at an angle alpha approximately equal to the angle of the repose of the natural ground 2. Then, an upper half annular segment ring 15 is erected in tunnel space 3 in such sate as following the device 5 and laid on the concretes 33 and 33, thereby constructing a lining body 30.