Influence of stratigraphic facies variations on the roof stability by physical modeling study

Controlled by depositional environment, the combined structure of roof rock layers behaves as vertical cyclically, thickening or thinning up to pinchout discontinuously in horizon. Thereby, the roof stability is dominantly dependent on it. In order to investigate how the roof sedimentary combined structure and thickness of sandstone influence on the roof stability during and after coal mining, a physical modeling study is conducted in this paper. It is shown that with stronger sandstone of roof strata, roof has a longer distance of initial weighting and periodic weighting, higher abutment stress on the coal workings, larger caving and fracture zone. It is quite different in case of roof rock-mass without any framework sandstone. While in the transition zone of nipped sandstone, roof rock-mass is broken and with poor stability.