Abstract
To improve the resource recovery efficiency of mining face in thick coal seams, the correlation between deformation failure of bottom coal in the gob-side entry and coal pillar width was analyzed by theoretical analysis, numerical calculation, and similar simulation experiments. The results showed that, when the coal pillar was strong, with the decrease of pillar width, the failure depth of the bottom coal in the gob-side entry and floor heave increased. The deformation failure depth of the bottom coal in the entry was inversely related to the width of the coal pillar. The bottom coal was further fractured and dispersed under the action of tension, shear, and extrusion in the process of floor heave. Based on the floor heave induced by the narrow coal pillar, a recovery technique of the bottom coal with thick coal seams in the gob-side entry was developed. The width of the narrow pillar to be reserved was obtained by theoretical calculation and revised by numerical simulation; ultimately, the reasonable width was determined. Under the complex stress of the narrow pillar, the bottom coal in the gob-side entry was fully heaved, cracked, and separated. To realize the comprehensive mechanization and resource recovery of bottom coal, a matching mining excavator loader, transfer conveyor, and retractable belt conveyor were selected to transport the crushed bottom coal in the entry. This method has been successfully applied to the return airway of working face 8407 in the No. 5 Coal Mine of Yangquan Coal Group with remarkable economic and social benefits.
Highlights
Coal, as one of the main energy resources, still accounts for 60% of primary energy consumption in China [1,2]
Over three billion tons of coal were produced in 2019, and 45% of coal production came from thick coal seams in underground coal mining [3,4,5]
Co., Ltd., the relationship between the failure depth of the bottom coal and the width of the narrow coal pillar in the thick coal seam mining roadway was studied through theoretical analysis and numerical simulation
Summary
As one of the main energy resources, still accounts for 60% of primary energy consumption in China [1,2]. The study on the induced mechanism of bottom heave by narrow pillars has a great significance for increasing the recovery ratio of coal resources. Research on the induced mechanisms of floor heave in roadways has been widely investigated [9]. Zhong et al [10] analyzed the occurrence mechanism and main influencing factors of the floor heave in soft-rock tunnels. Considering the post-failure deformation of rock, Wang et al [13] established a theoretical model based on the strain energy theory to analyze the floor heave. Co., Ltd., the relationship between the failure depth of the bottom coal and the width of the narrow coal pillar in the thick coal seam mining roadway was studied through theoretical analysis and numerical simulation. This study provides a reference to recover the bottom coal under similar conditions
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