Abstract: The device has a hollow cylindrical housing pointed at the front end and accommodating a hammer piston, which defines with the housing a front end work chamber and, which has at a rear end portion a cylindrical space and an open-ended radial passage. The cylindrical space receives the large portion of a stepped pipe in order to define with the hammer piston a rear end work chamber. The small portion of the pipe is received in the rear end portion of the housing for rotation about its axis within limits defined by a locking member and is connected, by means of a flexible hose, to a source of compressed air for permanent supply to the rear end work chamber of compressed air. The large portion of the stepped pipe opens the radial passage of the hammer piston at regular intervals to establish communication between the front end work chamber and the rear end work chamber, thereby enabling forward movement of the device.

Abstract: The apparatus has a pointed-nose hollow cylindrical body with a closed rear portion. Disposed inside the body, so as to enable reciprocation and rotation about the axis of the body, is a stepped striker which can be locked against rotation about the axis of the body in two positions, the positions corresponding to forward and reverse movement of the apparatus.For the purpose of admitting compressed air into a forward working chamber, the striker is provided with a central passage permanently connected to a rear working chamber and at least two radial passages which provide communication between the central passage and an outer cylindrical surface of a large step of the striker. The radial passages are displaced relative to each other both circumferentially and longitudinally along the axis of the body.

Abstract: Method consisting in forming a borehole in the ground preferably having a diameter smaller than the desired diameter of a pile, compacting a concrete mix poured into the borehole by repeatedly passing a pneumatic mole through the borehole filled with concrete to compact the concrete mix in the peripheral zone of the borehole thereby concurrently expanding the reinforcement.

Abstract: A percussive device comprising a housing with a pointed front end and a hammer piston accommodated in the housing to form a front working chamber therewith. The hammer piston is provided, in the rear portion thereof, with a cavity in permanent communication with a source of compressed air, the cavity serving as a rear working chamber. An airdistribution mechanism includes a tube mounted in the housing within the hammer piston cavity so that it is conjugated with the walls of the cavity, the piston having air passages therein positioned in such a manner that, during the reciprocation, the tube alternately communicates the front working chamber, via these passages, with either the rear working chamber or ambient atmosphere.