Pit prop for in situ casting has a water porous sheath with filling valve and with separate fitting valve for top of prop

摘要

A pit prop system for casting in situ has a plastic fabric sheath (7) of water porous construction filled via a valve (10) and allowed to set. The sheath is hung by integral straps (12, 13) from an overhead support and shrinkage of the filler is made up via other valves (16) in the padded top end (11) of the sheath. The additional filler is introduced at a slower rate before the main charge has set, to form a one piece casting.