Abstract: A method for breaking a hard compact material such as rock or concrete. The method includes drilling a hole into the material, gripping a portion of the wall of the hole by applying a radially outwardly directed force thereto, and applying an axially outwardly directed force to the gripped region in order to cause cracks to arise in the wall of the hole. One of the forces is generated by means of sequentially repeated axially directed impacts. The apparatus for carrying out the method comprises a gripping means and a wedge means slidable relative to the gripping means. The gripping means and the wedge means have cooperating wedge surfaces. A rear extension member having a shoulder is attached to the wedge means. A hammer piston reciprocable in the apparatus housing delivers sequentially repeated axially directed impacts upon the shoulder.

Abstract: A method of breaking hard compact material such as rock adjacent a hole drilled thereinto and an apparatus for performing the method are described. Two forces contribute to efficiently breaking the rock: a force for firmly gripping a region of material adjacent the hole and an axial outwardly directed force. When breaking the material the force for firmly gripping the material is unidirectional with but separate from the axial outwardly directed force. To generate these forces wedge means and sleeve means of the apparatus are inserted into the hole and an axial outwardly directed thrust is exerted on the sleeve means by means of cooperating sliding wedge surfaces of the wedge means and sleeve means which converge towards the apparatus power means. This power means as well as the thrust transmitting means for transferring the reaction force are situated outside the hole.

Abstract: A hard compact material, such as rock, is broken by delivering a hydraulic fluid, such as water, into at least one hole which has been pre-drilled in the material to be broken, the hole functioning as an hydraulic fluid cylinder. A piston is driven into the hole to impact the fluid to generate a high pressure in the fluid and to cause tensile stress cracks in the material by the established pressure. Due to the concentration of the stress at the bottom of the hole, the cracks are initiated and spread generally radially outwardly substantially normal to the principal stress direction. A plurality of said holes may be drilled and the cracks linked together by appropriate choice of form, depth, orientation, spacing and number of the holes. Preferably, the piston is driven into the hole by means of a gun at speeds ranging up to several hundred meters per second.