Geotechnical mechanisms of roof fall ahead of face support in longwall mining

Longwall mining is one of the most productive methods for extracting underground coal seams. Although the understanding of longwall mining-associated geotechnical mechanisms has been significantly improved that contributes to better ground control, roof rock/top coal fall ahead of support (roof fall) has not been fully understood that causes severe damage to equipment and casualty at face. Empirical, theoretical and modelling methods were successfully used in past studies to understand the mechanisms driving roof fall; however, key mechanisms and their interactions during the fall were not satisfactorily investigated due to limitation of each method. This study aims to gain a systematic understanding of roof fall mechanisms in longwall operation. A review of past studies on roof fall is implemented with emphasis on the principles of applied research methods. The study confirms that the interaction between roof strata, coal seam and face support largely controls roof fall while numerical modelling shows great potential in studying roof fall complex mechanisms. The paper’s findings provide mining engineers/scientists with a systematic understanding on roof fall from which more effective roof control strategies can be further developed.