Research Of Deep-ground Coal Bed Thick And Hard Roof Breaking Regular Pattern

Based on the disaster that the thick and hard roof while mine excavation, this paper research the crack theory of the deep coal bed under load, the regular pattern of the thick and hard roof breaking, the reasonable hanging distance and weighting step of the thick and hard roof. Finally, numerical simulation the crack situation of a common and the thick hard roof under the first and cycle pressure. The author integrated use of computer simulation values, and reach to the reliable data. The results are consistent with the theoretical results. The research suggest that:1. Introduced several theoretical and mechanics foundation of the rock crack, elaborated Griffith crack theory, Orowan correction theory, three types of crack and the rock crack toughness test, summed up the characteristics of rock crack mechanics properties.2. Initially identify the method to select the reasonably hanging distance and the pressure step of the thick hard roof of the deep-ground coal bed. Start from the movement regular pattern of the mechanized mining surface overburden, list three mechanics models of the roof surrounding rock, which is:elastic foundation plate continuous mechanics model, elastic foundation crack plate (beam) mechanics model, elastic-plastic hanging plate mechanics model. Finally, author introduce two types mechanics models of the thick hard roof surface, which is:the rock beam model and the rock plate model. Based on elastic-plastic theory, author introduce, analyze and finally derivate the first and cycle pressure step of both the rock beam model and the rock plate model, get the simplified formula of the first and cycle pressure step, identified that rock plate model is a more reasonable model than others in thick and hard roof in deep-ground coal bed.3. Author briefly introduce the numerical simulation software ANSYS. Then numerical simulation analyze both the first and cycle pressure step of both ordinary roof and thick and hard roof under the deep-ground coal bed, and compared with the theoretical values. It shows that ANSYS can simulate the actual situation well, and it is consistent with theory calculation. Finally, author compare the ordinary roof and the thick hard roof in deep-ground coal bed, and find the thick hard roof in the deep-ground coal bed has long caving step, large hanging area, large shearing stress along the working surface, strong pressure.This paper can guide the safe mining under thick hard roof in deep-ground coal bed mining surface and stope roof control, and this paper also has its reference value.