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Supports have developed according to the aperture and slope of the longwall concerned. Increases in load-bearing have generally been in response to problems resulting from the lie of the land. The study was carried out in two ways: an analytical approach which was as advanced as possible allowing for the available means and conditions at the bottom and an overall study using appropriate statistical methods. The latter confirmed the previous results but did not provide any new ones. On the other hand the analytical approach, applied at high performance working points, made it possible to specify the properties of the face by reference to the mechanics of the stratified deposits. Old results can be re-interpreted in the light of the new, and rules can be put forward for selecting the support according to the nature of the hanging roof. Two situations may be encountered: a) It is technically possible to envisage a load-bearing capacity which would prevent the roof from caving in at the face and would deposit it behind the support; under these conditions the required support can be calculated exactly. b) It is impossible to avoid crevasses in the face, and the support must prop up the blocks formed. Conventional estimating methods are used in this case.

Additional information

Authors: POIROT B, Cerchar, Tour Albert 1er, 65, Avenue de Colmar, F-92507 Rueil-Malmaison (FR)
Bibliographic Reference: EUR 12314 FR (1989) MF, 99 pp., ECU 8, blow-up copy ECU 12.50
Availability: (2)
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