| 摘要 |
A drill head 10A is domed at 26 and carries cutting teeth. A tubular drill string 16 can be used to drive the head 10A into the ground. An off-centre aperture 30 communicates with the bore 18 of the string 16, by means of a connecting passage 38, which defines an oblique cone. During drilling, a flushing medium can be pumped down the bore 18 and out through the aperture 30. As the drill string 16 and head 10A are withdrawn, an elongate member can be introduced down the bore 18, out through the aperture 30, to be left in the passage drilled by the head 10A. The form of the mouths 30, 36 and connecting passage 38 avoid the elongate member encountering any discontinuities which would prevent it leaving the head, as described. The elongate member could be reinforcing bar for a cast-in-situ pile, or part of a ground loop for a ground heat energy system. |
