Abstract: Method and apparatus for crushing the earth under the ground by boring a hole; inserting a drill head having radially directed water jet thereon down the hole to the desired stratum; rotatingly moving the drill head upwardly while jetting water radially to form a cylindrical crushed area; lowering the drill head to the original depth; extending a water jet extender arm radially to a projecting position; again rotatingly moving the drill head upwardly while jetting water from the nozzles on the radial outward portions of the extender arm to radially enlarge the cylindrical crushed area, the rotation of the extender arm also stirring the already crushed area; returning the extender arm to an original waiting position; and lifting the drill head out of the hole.

Abstract: This invention concerns with a high pressure grouting process. For lateral cutting of earth in the ground, a high speed core water jet, having its injection velocity equal to at least a half of the sonic one and surrounded by an air ring jet is used. For solidifying the crushed earth, a cement milk is used which is poured separately and at a lower level than that of the air-water combined jet into the space in the ground which space has been formed by the action of the core water jet.

Abstract: The method of digging by piercing soil and rock with a jet of liquid discharged at high velocity from a nozzle together with high-velocity air jets discharged from another nozzle arranged concentrically around the liquid nozzle, characterized by the velocity of the air jets being at least half the velocity of sound.