Abstract:  In order to better control and avoid the roof accidents, we put forward the roof accident prevention and control system of “roof caving mechanism-roof control design- roof support quality and dynamic monitoring-roof accident warning” in this paper. In addition,  taking separation type roof accident as research object, considering the roof as isotropic body, and simplifying the movement and destruction of strata as simply supported beam, we deduced the calculation formula for critical separation area Smax of roof breakage according to the deflection curve equation of simply supported beam, and proposed Smax as the warning criterion of separation type roof accident. Through the engineering example analysis, the accuracy of Smax warning criterion for separation type roof accident is verified.

Key words:  roof accident, critical separation area, warning criterion