Abstract: By the means of force equilibrium analysis of the arc roof, four major factors affecting its balance have been identified. The four key factors have been used in the simplification of irregular triangular body model. And the formula for calculating volume change during the roof caving has been derived, which has indicated that if the sum of the volume change during roof caving, volume change of work surface interior and the lower corner during weighting process substracts the air leakage into goaf, the incremental value of emission gas from the upper corner position during the weighting process can be calculated. By analyzing the upper corner CH4 volume fraction monitoring records of four mine working face, the change rule of upper corner gas volume fraction during the weighting process has been concluded, which has shown that the upper corner gas emission is influenced by the upper arc roof. With periodic roof caving, emission of upper corner gas has significantly increased periodically. According to the air monitoring data near upper corner of Kangcheng and Yunjialing coal mine, the increased air volume of upper corner during the weighting process has been conducted. Based on the comparison between the measured data and theory calculation, the error is less than 5%.

Key words: curved failure, periodic fracture, rotary disturbance, upper corner