PIT MOUTH STRUCTURE OF STARTING PIT WALL AND ARRIVAL PIT WALL IN PROPULSION METHOD

摘要

PROBLEM TO BE SOLVED: To prevent damage of a seal material due to a drilling machine while guaranteeing cut-off action in pit mouths a, b of a starting pit A and an arrival pit B.SOLUTION: There is provided a pit mouth structure of a starting pit and an arrival pit in a propulsion method for constituting a pipeline connecting a propulsion pipe from a starting pit to an arrival pit by press-fitting a drilling machine 1 and a propulsion pipe T into the ground while drilling the foundation G with the drilling machine 1 from the starting pit toward the arrival pit. In pit mouths a, b, concentric movable cylindrical bodies 13, 23 are fitted in a movable manner in the axial direction in a circular hole 11 with inner diameter larger than the drilled bore of the drilling machine, and seal materials 12, 22 contacting the external cylinder of the drilling machine and the whole circumference of the outer peripheral surface of the propulsion pipe are provided in the whole circumferences of the inner surfaces or the whole circumferences of the outer surfaces of the movable cylindrical bodies. At this time, there is no damage in the seal materials since the seal materials do not contact with a rotating drilling blade, and the movable cylindrical bodies are moved following the movement of the drilling machine, therefore the cut-off action with the outer peripheral surface of the drilling machine is guaranteed by the seal material. Consequently, the axial length of the pit mouth can be shortened by the amount of movement in the starting pit, and recovery of the drilling machine is facilitated in the arrival pit.