| 摘要 |
Hollow drills for forming stone columns are known however the material being fed through the hollow drill can bridge or not compact as intended and as such a less than ideal stone column can be produced. In addition the granular material used to form the column and the surrounding ground material, or even adjacent column material, can migrate inwardly compromising the integrity of the stone column formed. The present invention provides a drill unit for forming a column in ground which includes an outer drill, where: - the outer drill is a tube which includes a first cavity, a first outside surface and a first terminal end; - the first cavity is an interior void extending along the outer drill which, in use, provides a pathway for material used to form the column to exit at the first terminal end; - the first outside surface is an exposed outer surface of the outer drill; and - the first terminal end of the outer drill is the terminal end of the outer drill that, when the drill unit is in use, enters, or is within, the ground; such that attached to the outer drill there is at least one drill tooth which includes a first face, a second face and a base face wherein: - the first face and the second face are immediately adjacent one another and are coterminous at a first edge and a second edge; - the base face is the face closest to, or coterminous with, the first terminal end; - all faces, except the base face, are independently coterminous with the base face; and extend away from the base face in the same direction; - at least part of the at least one drill tooth extends away from the first terminal end to terminate at the second edge; - the second edge is the edge of the at least one tooth that is most longitudinally distant from the first terminal end; - the first face further includes a first alpha edge, where the first alpha edge is an edge of the first face opposite the first edge; - a line joining the first edge and the first alpha edge, where the first face and the base face are coterminous, a first face alignment line, is at an angle of ɸ to a perpendicular extending from the first outside surface; - the second face further includes a second alpha edge which is an edge of the second face opposite the first edge; and - a line joining the first edge and the second alpha edge, where the second face and the base face are coterminous, a second face alignment line, is at an angle of &thetas; to a tangent on the first outside surface; such that, when in use forming the column, the first edge is configured to be a leading edge. The tooth is intended to guide material away from the first cavity to form an improved stone column of improved consistency and density by minimising the amount of foreign material incorporated into the column. The tooth also acts to improve the density of the wall of the column formed. |
