| 摘要 |
<p>A tunnelling machine is provided with three flushable zones 23, 31, 41 including a forward crushing zone 23 adjacent a cutter 26, a rear zone 41 and an intermediate zone 31. A flow control device 43 is provided to provide variable control of flow of material from the intermediate zone to the rear zone. A valve 60 selectively diverts water to the three zones. The arrangement enables the machine to tunnel through various types of material by adjustment of the valve and the flow control device. The valve is designed to permit back-flushing without blockage. <IMAGE></p> |
