| 摘要 |
During excavation of the hole, the spoil (5) is dumped onto a support (14), which is tipped on completion of the work below ground level for back-filling. The excavation work may be for e.g. the laying of cables and piping, the hole being oblong, with excavation, laying and backfilling taking place simultaneously at different points. This can be done where space is limited, e.g. along a railway track. The support can comprise a tipping frame to which a supporting component of folding material is fixed. Tipping is by a pneumatic ram acting between this frame and a fixed one. Alternatively a sack which can be filled with gas can be used, this being so shaped that its top surface slopes on inflation.
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