Mine Design To Maximize Coal Extraction In Longwall Mining

One of the most difficult problems associated with modern mechanised longwall mining is the lack of system flexibility to deal with local changes in geology, seam thickness and the face design parameters. As a consequence of system rigidity and the quest for increasing the coal face performance, the percentage extraction in the U.K. is currently below 52%. The paper outlines the current guidelines used in face design which permit coal to be left in situ for various purposes and discusses the strata control implications in extracting subsequent panels in the same and adjacent coal seams. The paper examines the application of strata mechanics to the design of longwall layouts for maximizing .the percentage of coal extraction. Remedial measures include optimizing pillar dimensions, reduction in roof coal left for support purposes by improving the use of available powered support technology and application of thick seam mining methods including sub-level caving and techniques of extracting coal from odd shaped pillars. Case studies are described where coal extraction has been maximized by adopting a new single heading retreat mining system; a shallow seam partial extraction system utilizing, existing heading machines and minimisin8 coal sterilization in pillars by replacing longwall access roadways by goaf scour.