| 摘要 |
A drill unit for forming a column in ground which includes an outer drill and a concentric inner drill, where 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 θ 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. |
