Abstract: For achieving better surrounding rock control in shallow working face, the mechanism of abnormal overlying strata behavior such as large-scale shear-caving along the rib is analyzed in this paper. The scale between the height and the length of key block increases because of the increase of the overburden load, mining height and the length of working face. Limit position of rotary instability is obtained according to the principle of minimum potential energy. The slope of horizontal extrusion pressure curve decreases while the slope of the height of articulated surface increases in the turning process of the key block because of increasing of the scale between the height and the length, and the allowing rotation angle before the hinged structure turning to the limit equilibrium position also increases, which is not likely to cause rotary instability of the hinged structure. However, sliding instability is apt to occur. According to the specific instability form of shallow high-intensity mining face, dynamic method for the determining of the supporting resistance is put forward, then first weighting of 31402 working face in Wulanmulun Mine is analyzed.

Key words: shallow working face, main roof, broken block, the scale between the height and the length, rotary instability, sliding instability