A new cavability assessment criterion for Longwall Top Coal Caving

This paper describes the main results of project aimed at developing a new cavability assessment criterion for top-coal, and improving the overall understanding of the caving mechanism in Longwall Top Coal Caving (LTCC) technology. The research methodology for this study incorporated a combination of analytical, observational and empirical engineering methods. The two major outcomes of the study were an improved understanding of the caving mechanics, and a new cavability assessment system, the Top-Coal Cavability Rating (TCCR). New conceptual models were introduced for better understanding of top coal caving mechanism. The results of the conceptual investigations suggest that six major parameters can influence the cavability of a typical coal seam, i.e. 1—deformation modulus; 2—vertical pre-mining stress; 3—sub-horizontal pre-mining stress; 4—seam thickness; 5—spacing of sub-horizontal joints; and 6—spacing of sub-vertical joints. The applicability of TCCR system was investigated by back analysing the cavability in earlier LTCC practices.