Displacement discontinuities and stress changes between roof strata and their influence on longwall mining under aquifers

Summary The results of physical model tests are analysed with special attention to the development of displacement discontinuities (bed separations) at the two stages of roof stratum movement over a longwall coal face. The relationships between roof displacement and stress concentration or relief are explored. The stress-displacement relationship is further examined by an analytical model, based on the assumption of laminated rock beams, which is used to identify possible displacement discontinuities in the roof strata which would form water inflow passages from an ovelying aquifer. Also demonstrated is the potential of the analytical model for serving as a theoretical approach or, at least, a complement to empirical methods in estimating the critical and the safe distance of mining under an aquifer.