Shallow Seam And Large Mining Height Working Face Roof Structure And Stability Research

In northern shaanxi, shallow seam reserves abundant and large mining height technology applies widespread. With the mining height increases, not only support selection is increasing, but also support costs continue to increase, reasonable working resistance identified is short of scientific basis for restricting the safety and economic exploitation. Research shallow seam and large mining height working face roof structure and stability, determine a reasonable bracket resistance has important theoretical and practical significance.Through shallow seam 4m, 5m, 6m, 6.8m large mining hieght working face measured data analysis, derived with mining height increases, support resistance is increasing, especially mining height reaches 6.8m, the working resistance increases rapidly, dynamic load coefficient increased general gentle. Coal of zhang jia mao and san dao gou coal similar physical simulation experiment result: shallow seam and large mining height working face lead abutment pressure away from coal mining height of the wall of coal is about 2 times, the influence of peak is range to 60~80m, increased stress coefficient average value was 1.72 times rock stress. With the increased mining height, increasing the thickness of equivalent immediate roof. The study found that the change thickness of equivalent immediate roof is a major factor in large mining height roof structure effects; Failure modes of equivalent immediate roof have a significant effect on the characteristics of large mining height to pressure. Because of the equivalent immediate roof thickening, mian roof structure hinged position constantly on the move, goaf does not fill the full, the lower key stratum of main roof presented " lean step voussoir beam " structure, the upper key stratum of main roof presented " masonry beam " structure, working face pressure major influence is the lower key stratum structure.According to equivalent immediate roof collapsed different structures of filling,the large mining height equivalent immediate roof is divided into three types,namely fully filling type,general filling type and less filling type, equivalent immediate roof and mining height ratio have an effect on the filling rate of collapse.For the main roof breaking located the wall of coal and the rear walls of coal conditions, established the large mining height working face roof " lean step voussoir beam " structure model, obtained the two conditions support working resistance calculating formula,through engineering examples demonstrate the models and formulas. Analysis of the equivalent immediate roof thickness, the length of main roof, the key stratum thickness of mian roof, the key stratum breaking angle of mian roof, the breaking angle of equivalent immediate roof, the key stratum of mian roof is away from breaking point to the rear wall of coal roof support resistance impact.