DefinePK

Abstract

Roof strata tend to have sagging effect due to gravity loading, in the zone of extraction under bord and pillar underground coal mining with caving, with subsequent development of mining induced stress which keeps on increasing gradually with extractions. Such induced stress may influence workings as dynamic loading effect, posing as a threat to stability of working geometries. In general, when the cavable roof strata are considerably weak in formations, such loading effect remains within the goaved out area, resulting to a safer caving scenario. But, under such situation, presence of any weaker working geometries nearby, such as rib extraction zone, geologically disturbed places etc. may attract the dynamic load to get released with possibilities of sudden premature strata failures. The effective preventive measure for such adverse situation is to go for proper study of strata movement to predict / apprehend the peak limits, so that suitable control measures including roof & side support actions may be actuated. This is a study for analysis of strata behavior under weak roof formations during depillaring with caving and predicting / apprehending the safe limits of strata movement by working over the ‘Roof Fall Warning Index’, already developed by the principal author. For the study, information were used on different main falls from the depillaring panels of two different underground coal mines with weak and easily cavable roof strata.