DOUBLE TUBE HOLE DRILLING DEVICE AND ANCHOR MATERIAL ARRANGING METHOD USING SMALL DIAMETER DOUBLE TUBE HOLE DRILLING DEVICE

摘要

PROBLEM TO BE SOLVED: To improve workability of a natural slope stabilizing construction method, by providing a double tube hole drilling technology having the spinning powder discharge function particularly effective in a small diameter, for precisely and stably transmitting impact force, and further smoothly discharging spinning powder, in a limited outside dimension of an impact force transmitting diametrally expansive part formed on the inner bit side.;SOLUTION: An outer bit 6 is constituted to be capable of advancing and retreating to an outer pipe 2, and for transmitting impact force applied to an inner bit 5 to the outer bit 6, the diametrally expansive part 10 having a locking part engageable with the outer bit 6 side, is formed on the inner bit 6 side. A divergent discharge groove 13 communicating with a discharge passage 14 formed in an outer peripheral part of the inner bit 5 and having a lateral width gradually expanding to the downstream side, is formed in its diametrally expansive part 10. A bottom surface of the discharge groove 13 is also formed in a slope shape to substantially coincide with an outer peripheral surface on the down-the-hole hammer side in a downstream side end part by gradually diametrally expanding toward the downstream side.;COPYRIGHT: (C)2007,JPO&INPIT