Abstract: A grab having at least one shoe for support against the walls of the hole that the grab is digging, and elements for moving the shoes between a folded-in position in which they remain alongside the frame and an unfolded position in which they press against the walls of the hole. Preferably, unfolding of the shoes is performed automatically when the grab reaches the bottom of the hole. The excavator of the invention is provided with such a grab. A very high digging force is achieved without an increase in the volume or in the weight of the grab.

Abstract: A method for making foundation piles in soil with a drilling device having an auger, the auger including two concentric tubes, an outer tube occupying an upper part of the auger and an inner tuber projecting partially as a prolongation of the upper part and occupying a lower part of the auger, the inner tuber having a first screw and the outer having one of a second screw and a plurality of blades, both of said tubes being displaceable with respect to each other, the method including the steps rotating the inner tube in a first direction, simultaneously rotating the outer tube in an opposite direction of the first tube and advancing the auger through said soil whereby the soil is compacted against a wall of a formed hole by the combined action of the first screw and the one of the second screw and plurality of blades of the inner and outer tubes.