Staggered development based method of mining for underground extraction of a critically[1] thick coal seam standing on pillars and development made along the roof horizon
Selection of a suitable mining method for a critically thick coal seam, developed on pillars along the roof, is an extremely challenging and complex problem. Extraction of top section first may jeopardize the scope of safe extraction of bottom section i.e. the coal left along the floor. An idea of staggered development based depillaring by caving of whole seam in one lift is conceived for safe, efficient and economical working of the seam. Staggered development of bottom section was supported by laboratory investigations on simulated models and it can be used to extract complete thickness of the seam in one lift. Field validation is in progress under an S& T Project of Ministry of coal and patent application has been filed for this method.
[1] Superimposed development is a statutory requirement for contiguous sections. While, on the other hand, minimum 3m thickness of the parting is must between the workings of two close/contiguous sections/seams. Critically thick seam are those, which do not provide the required minimum 3m thickness of parting between the two contiguous sections to be developed for optimal exploitation of the seam.