Abstract: To analyze the roof first caving span based on the plate structure theory, considering the roof strata are loaded by continuous linear action, the roof first caving spans in the simply supported and clamped boundaries were investigated respectively by using the theoretical analysis and field measurement. In this paper, the relationship between the bending moment in the rupture peril point of roof and ratio of roof length in the two directions (strike and inclined directions) were obtained, and the largest bending moment expression under the random length ratio of the two directions were provided. Meanwhile, the largest stress distribution expressions in the simply supported and clamped roof boundaries were obtained when considering the trapezoidal loading of the inclined roof. Moreover, a simple calculation method for roof first caving span based on the plate structure theory was proposed. According to the contrast results between the field measurement and theoretical analysis of the roof first caving span in 8281 coal face in Taoyuan mine, Huaibei mining area, the measured first caving spans which are ranging 25~34 m basically match the theoretical calculation results (26.5~35.5 m), which indicates that the calculation method has good adaptability for the roof first caving span forecasting.

Key words: plate structure theory, caving span, trapezoidal load, roof bending moment