E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
E21D15/00—Props; Chocks, e.g. made of flexible containers filled with backfilling material
E21D15/14—Telescopic props
E21D15/16—Telescopic props with parts held together by positive means, with or without relative sliding movement when the prop is subject to excessive pressure
E21D15/20—Telescopic props with parts held together by positive means, with or without relative sliding movement when the prop is subject to excessive pressure with pawl, pin, cross-piece, or the like engaging with ratchet teeth, notches, holes, or the like, spaced apart at intervals
Landscapes
Engineering & Computer Science
(AREA)
Mining & Mineral Resources
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Mechanical Engineering
(AREA)
Structural Engineering
(AREA)
Life Sciences & Earth Sciences
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General Life Sciences & Earth Sciences
(AREA)
Geochemistry & Mineralogy
(AREA)
Geology
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Refuge Islands, Traffic Blockers, Or Guard Fence
(AREA)