Patent ID: 7192220

Claim:
A rotary tool for drilling into a soil formation from its surface, controllably injecting water and dry binder at known depths below the surface of said formation, and mixing said soil, water and dry binder to form an in-situ piling, said tool comprising: a rotary shaft having a central axis of rotation adapted to be driven bi-directionally around said axis, and bi-directionally along said axis; a vane on and extending radially from said shaft to be rotated around and moved axially by said shaft, said vane being so disposed and arranged as to move through the formation along a helical path to drill into said formation, to stir the material of the formation, and ultimately to mix the material of the formation with water and dry binder; a water injector and a binder injector carried by said tool, each injector having a respective axis of emission of water or of dry binder, said axes of emission being directed away from said tool into said formation at a respective location along said central axis; said injectors being so disposed and arranged relative to one another that the material of their emissions will during a limited number of revolutions of said shaft, encounter one another, there to be mixed as a pre-determined ratio of water and of dry binder, said water including water emitted from the water injector and water which may have already been present at that location; said injectors being set in said shaft with their axes of emission substantially normal to said central axis, and located along said central axis such that the emission of one of them will, within a limited number or rotations of the shaft encounter and mix with the other in a temporally suitable time related to the curing of the binder and drainage of the water; there being a pair of said water injectors and at least one of said binder injectors set in said shaft, with said binder injector located axially between said water injectors.