Abstract: A tool comprises two coaxial casings, a leading and a trailing ones, connected by a tubular element provided with ports for discharging a fixing material into a hole. The leading casing comprises a cylindrical portion, and frontal and rear conical tips provided with spiral tapered surfaces intended for consolidating soil. The trailing casing has a cylindrical portion of a greater diameter than that of the cylindrical portion of the leading casing. In the trailing casing there is provided an axial duct communicating with a cavity of the coupling element for supplying a fixing material. A method of forming holes having fixed walls includes formation of a pilot hole using the leading casing, and subsequent formation of a hole of a predetermined diameter using the trailing casing in the advancing sinking of a pilot hole.

Abstract: A tool for the formation of holes without extracting the soil comprises a body having a cylindrical calibrating portion, coaxial portions with surfaces for the compaction of the soil and radii decreasing stepwise in the direction away from the calibrating portion, and terminating in an end piece. The body has also transition portions with surfaces for the compaction of the soil, forming a smooth transition from a coaxial portion with a larger radius to an adjacent coaxial portion with a smaller radius. The surface for the compaction of the soil of each coaxial portion is a conical surface having the configuration of a ribbon wound from the calibrating portion to the end piece and comprising the transition portions.