Secondary settling

SECONDARY SETTLING within the underground mine (EN: secondary settling; DE: wiederholtes Absetzen; FR: affaissement secondaire; ES: hundimiento secundario; RU: вторичная осадка) is the spontaneous periodic settling of the rock within the roof of the longwall stope during the process of its movement. The secondary settling is the consequence of the disturbance of the equilibrium state of the massif of the overlying rocks, prevalently within the major roof. The process proceeds intensively, is accompanied by the dynamic bumps within the zone of the influence of the clearing mine working, by the settling of the individual and powered roof supports within the significant areas of the space near the longwall stopes, and by the sound effects.

The parameters, which are characterizing the secondary settling: the magnitude and speed of the lowering of the roof (the major parameters), the area, which is subjected to the settling, the duration of the secondary settling, the interval of the secondary settling along the strike (along the dip), and the frequency. The manifestations of the secondary settling, and their parameters, are mutually associated with the modes of the work of the roof supports within the clearing stope. The secondary settling is taken into account during the compiling of the classification of the rocks within the roof according to the tendency to collapse. For the purposes of the prevention of the harmful influence onto the work of the clearing stopes, the secondary settling is taken into account during the choice of the method for the control over the rock pressure. In case of the development of the tabular deposits (coal, manganese, and so on) with the roofs, which are difficult to collapse, there are performed the additional activities, which are excluding the manifestation of the sudden settlings of the rocks within the major roof (the leading torpedoing or hydroprocessing of the rocks within the major roof, the stowing within the goaf space, the preliminary underworking, and so on).