METHOD FOR PREVENTING DETACHMENT OF OUTER TUBE IN UNDERGROUND DRILLING OPERATION

摘要

PROBLEM TO BE SOLVED: To prevent an outer tube from being extruded outwardly together with an inner tube under the operation of pulling out the inner tube while leaving the outer tube in the ground after drilling by means of a drill rod having a double-tube structure composed of the outer tube and the inner tube and enable the prevention of the outward extrusion of the outer tube under the operation of injecting a filler into the outer tube left in the ground. SOLUTION: A cylindrical elastic body 2 is interposed between the outer tube 1a and the hole wall of a drilled hole 3a in the vicinity of an insertion opening 3b, and a nut 3a screwed to the outer end of the outer tube 1a is rotated and made to progress in an underground direction. Consequently, the radial expansion of the elastic body 2 permits the elastic body 2 to be attached to the inner wall of a drilled hole 4a by pressure for the purpose of firmly fixing the outer tube 1a.