Study on top-coal recovery ratio distribution law of longwall top-coal caving mining in steeply thick coal seam

In order to grasp the distribution law of top- coal recovery ratio of longwall top- coal caving mining in steeply thick coal seam and improve the coal resour ce recovery ratio, the 3D loose top- coal drawing experiment, numerical simulation and field test were applied to analyze the top- coal recovery ratio from the aspects of shape of top- coal drawing body and the boundary of top- coal. The results showed that the top- coal recovery ratio shows“π 'shape distribution along the dip direction i n the 3D loose top- coal drawing experiment; the drawing body had an obvious developing tendency towards the upper end of the working face; the difference value of t op- coal loss at the upper and lower end of working face resulting from the' jujube core shape' of drawing body and the asymmetry of interface between coal and rock wa s the root cause of the“π”shape distribution of top- coal recovery ratio. Such distribution law was also verified by the numerical calculation and the filed test.