Patent ID: 7341405

Claim:
A method of preparing an in-situ piling in soil, the soil which occupies the situs of the intended piling constituting aggregate soil into which binder and water will be mixed to form said piling, said method utilizing a tool having a central axis of rotation, said tool having a head adapted selectively to be driven rotationally in both directions around said axis, and selectively driven axially in both directions along the axis, said head including at least two blades extending radially away from said axis, said blades depending at an angle relative to a plane normal to the axis so as to tend to move into the soil when rotated in a first direction, pressing down into it, and cutting into the soil, and to move into substances above it when turned in a second, opposite rotational direction and drawn axially upward, said blades having confronting edges, said method comprising the following steps in the order recited: a. rotating the tool in said first direction, while forcing the head into the soil in the situs, injecting water into the bore at said head to provide water to provide lubrication for the blades and for incorporation in an interface formed in the soil when it is pierced by the blades, and also to provide at least part of the water needed for hydrating binder that is to be injected into the situs; b. during step a, injecting from the tool into the situs less than the amount of binder ultimately required to form the piling, at a rate of supply along the length of the intended piling respective to the anticipated amount of binder required for bonding of the type of soil at respective depths to form a piling, said binder being injected along with air under pressure; c. after finishing step b, rotating the head in said second direction and pulling it from the situs, while adding additional binder and water in an amount at each depth which with the binder and water already added in steps a and b will provide a stoichiometric mixture of binder, soil, and water and also water in excess of the stoichiometric requirement, along with air under pressure used to inject said binder; d. the rate of axial removal of the tool and its rate of rotation in step c relative to the rotation and rate of entry of the tool in step a being such that the vane will have impacted substantially the entire volume of material in the situs, thereby thoroughly to mix the material and reduce the particle size of the soil; e. removing the tool from the situs and permitting the mixed materials to cure to form the in-situ piling, the amount of water supplied during steps a, b, c and d being in substantial excess of the amount required to furnish sufficient water for stoichiometric hydration, and sufficient that in step d, the mixture of binder, aggregate and water is sufficiently fluid that a substantial portion of the air which was injected in steps b and c can percolate through the mixture to the surface and escape from the mixture.