E21D—SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS
E21D15/00—Props; Chocks, e.g. made of flexible containers filled with backfilling material
E21D15/50—Component parts or details of props
E21D15/51—Component parts or details of props specially adapted to hydraulic, pneumatic, or hydraulic-pneumatic props, e.g. arrangements of relief valves
E21D15/517—Extension elements
Landscapes
Engineering & Computer Science
(AREA)
Mining & Mineral Resources
(AREA)
Mechanical Engineering
(AREA)
Structural Engineering
(AREA)
Life Sciences & Earth Sciences
(AREA)
General Life Sciences & Earth Sciences
(AREA)
Geochemistry & Mineralogy
(AREA)
Geology
(AREA)
Tents Or Canopies
(AREA)
Pit Excavations, Shoring, Fill Or Stabilisation Of Slopes
(AREA)