Abstract
Aiming to reduce the high mining stress observed in large-space roof structures during mechanized mining of thick coal seams, a control technique based on protective-seam mining is proposed. This technique was used to investigate the 8108 working face of the No. 3–5 thick coal seam of the Tashan mine located in the Datong area of Shanxi, China, by means of simulations and field measurements. The numerical simulation revealed that the No. 3–5 coal seam undergoes expansion and deformation, accompanied by stress relief due to the mining of the overlying No. 4 coal seam. The physical simulation demonstrated that mining the protective seam changes the structural characteristics of the overlying strata in advance and reduces the integrity of the roof in the No. 3–5 coal seam. Field measurements showed that the support loads in the 8108 working face are significantly weaker than those in the adjacent 8107 working face, where protective-seam mining was not performed. In the absence of high resistance on the support and distinct periodic weighting characteristics, the rock masses around the 8108 working face and roadway could be easily supported.
Highlights
In China, the mining of coal seams thicker than 14 m accounts for 44% of the reserve coal resources.A sublevel-caving method is widely employed for mining because of its high efficiency and output.when mining thick coal seams, the strata are likely to move over a wide range because the mining height is considerable, leading to complex and potentially violent strata behavior [1,2,3,4,5,6].This is so when the coal seam is covered by an overlying hard roof that breaks during mining
When mining thick coal seams, the strata are likely to move over a wide range because the mining height is considerable, leading to complex and potentially violent strata behavior [1,2,3,4,5,6]
The results suggest that protective-seam mining is an effective method effective method of controlling adverse strata behavior while mining thick coal seams
Summary
In China, the mining of coal seams thicker than 14 m accounts for 44% of the reserve coal resources. When mining thick coal seams ( super thick), the strata are likely to move over a wide range because the mining height is considerable, leading to complex and potentially violent strata behavior [1,2,3,4,5,6] This is so when the coal seam is covered by an overlying hard roof that breaks during mining. To control the high mining pressure occurring in the overlying structures, hydraulic fracturing and blasting has been developed to deal with the stress concentration based on weakening the hard roof [5,10,11,12,13,14]. Hydraulic fracturing is achieved by using fracturing equipment and high pressure water [12]; the blasting is done by placing an explosive in the borehole [14] Through such methods, the overlying strata with well-developed fractures are more likely to cave. The method employed is feasible and effective in controlling the high mining pressure in large mining spaces while mining the thick coal seams
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