| 摘要 |
<p>The tool comprises a body (40) with a lower end (42) provided with several mechanical cutting parts (44) and with nozzles (46) for creating a pressurized fluid jet for breaking up the ground. It has an upper end (48) provided with connections (50) to a drilling string and a pressurized fluid supply. A valve (56) gives the pressurized fluid jet a temporary non-symmetrical distribution relative to the tool longitudinal axis.</p> |
