| 摘要 |
<p>1. Method of drilling in rock or gravel soils, in which the drillings are conveyed outwards out of the drilled hole along a directed drilling column by means of compressed air exiting from the drill during drilling against the drill advance direction, characterized in that the exiting compressed-air jet, without any substantial effect resulting from the wall of the drilled hole, forms, in the immediate vicinity of the exit opening(s) (18) leading out of the drill, a self-contained compressed-air jet annular in cross-section and directed substantially axially upwards.</p> |
