Abstract: By using UDEC software, we have simulated the coal wall deformation and spalling processes when the mining heights of longwall face in shallow seam are 4，5，6，7 m，respectively, and found that the coal wall spalling of large mining-height presented “vertical slice” failure feature. Then, the vertical slice mechanical model was set up. The results show that the most easily spalling position is at the 0.6 times of mining height through the deflection analysis of vertical slice. In addition, with the increase of mining height, the width of coal wall plastic zone, the vertical slice number, and the horizontal deformation of vertical slice will increase, while the stability of vertical slice will decrease. The stability of coal wall can be effectively improved, and the coal wall spalling will be well controlled, by enhancing the roof support, speeding up the mining speed, protecting the coal wall properly, and improving the constraint conditions of coal wall vertical slice.

Key words: large mining height, spalling mechanism, vertical slice model, numerical simulation