POWER ELEMENT FOR BREAKING ROCK

PURPOSE:To exert the action of radial compression on a porous wall so as to strengthen the ability of a power element to break rock by providing a protrusion on a wedge for supporting a thrust member, in the power element that includes the thrust member, a rubber tube and the wedge. CONSTITUTION:Two thrust members 3 of circular cross section of a power element 1 are arranged opposite to each other into cylindrical shape, and the two members are supported from inside by two wedges 2. A rubber tube 5 having one end closed is disposed between the wedges 2 and each of the wedges 4 is driven outward by expansion of the rubber tube 5 so as to expand the thrust members 3. A protrusion 6 is mounted to each of the wedges 4. When the power element 1 is actuated the thrust members driven by the wedges expand the porous wall end at the same time the protrusion 6 protrudes outwardly from a space between the thrust members and invades into the porous wall so as to accelerate propagation of cracks.