Mechanical analysis of main roof breakage with dip oblique coal mining method

In order to understand the mechanism of main roof breakage with dip oblique coal mining method,this study investigated the breakage of mine main roof,established a mechanical model and obtained a support load function once the main roof was caved based on the elastic thin plate theory.Using the Rayleigh-Ritz method and the deflection superposition principle,a main top deflection function was derived and a basic roof breaking process was analyzed based on the caving process in a mined-out area with the dip oblique coal mining method.The results show that the asymmetry of the main roof deflection occurs because of the incomplete caving of falling gangues in vacant place with the dip oblique coal mining method.The maximum deflection is 60.9 cm,located in the upper part of caving roof.The main roof breaks into various sections from upper to lower section,and forms a relatively stable hinged structure.The distances of break between sections are also different,the breakage distance in upper part is less than that in lower part.Also,the theoretical calculation results are consistency with the site mine pressure monitoring.