| 摘要 |
<p>PROBLEM TO BE SOLVED: To increase efficiency of a crushing operation performed by a wedge type chisel, by restraining the wedge type chisel from being engaged in a drilled hole.SOLUTION: A wedge type chisel includes a first rock breaking part 12 that assumes a tapered shape toward a tip. The wedge type chisel breaks a rock around a drilled hole by having the tip pushed into the drilled hole formed in a first direction (+X) with respect to an object 2 to be crushed and thus making a side surface of the first rock breaking part 12 push an inner wall of the drilled hole in a second direction Y orthogonal to the first direction (+X). A crack introduction part 15 is provided on a tip side with respect to the first rock breaking part 12. The crack introduction part 15 has a crack introduction surface 16 that is inclined so that a tip-side outside diameter can be smaller than an inside diameter of the drilled hole, so that an outside diameter can become larger toward a back end side and so that a back end-side outside diameter can be larger than the inside diameter of the drilled hole. An angleθ16 of inclination of the crack introduction surface 16 with respect to the first direction (+X) is larger than an angleθ13 of inclination of a side surface of the first rock breaking part 12 with respect to the first direction (+X).</p> |
