Caving mechanisms of loose top-coal in longwall top-coal caving mining method

The top-coal caving mining method, developed steadily in the past two decades, has become the main method for thick seam coal mining in China. In recent years, the core research areas in the top-coal caving mining are the mechanisms of top-coal caving and the improvement of top-coal recovery ratio. In this paper, the mechanisms of the top-coal caving are illustrated by a large number of physical simulation experiments and numerical modelings of actual cases. The marker method, which has sufficient accuracy to calculate the top-coal recovery ratio, is also described in detail.