EXCAVATING TOOL

PROBLEM TO BE SOLVED: To form a drilled hole without loosening a stratum or making a void, by suppressing the diffusion of air into the surrounding stratum, even when cuttings are discharged by discharging the compressed air to the leading end side of a tool body in the excavation of highly-permeable stratum. SOLUTION: A cylindrical member 12, the center of which is an axis line O, is arranged on the outer periphery of the leading end 2 of the tool body 1 formed in an disc-like outer shape centering on the axis line O; an inner peripheral surface of the cylindrical member 12 faces the outer peripheral surface of the leading end 2 of the tool body 1 at a spacing between them; and a compressed-air supply hole 13B formed in the tool body 1 is opened on the outer peripheral surface of the leading end 2 of the tool body 1, facing the inner peripheral surface of the cylindrical member 12, via a decompression chamber 14 having an area of an opening on the outer peripheral surface set larger than a cross-sectional area of the supply hole 13B. COPYRIGHT: (C)2010,JPO&INPIT