| 摘要 |
<p>The system is used for opening up cavities in an underground coal mine. Break-in is effected by hydromechanical attack produced by one or more jets of water from a nozzle, the rest being extracted by widening, after which the nozzle is moved on. During the break-in process, the nozzle (12,13) is guided along, as the hole becomes deeper. The break-in is opened up, with a min. cross-section permitting introduction of water jets across the borehole axis. With these, widening is effected from inside, by hydromechanical engagement of the faces (18,19). Large proportions of the cross-section can be extracted with high output, and sharp limitation of the hole size is possible.</p> |
