Abstract
For sustainable utilization of limited coal resources, it is important to increase the coal recovery rate and reduce mine accidents, especially those occurring in the entry (gateroad). Entry stabilities are vital for ventilation, transportation and other essential services in underground coal mining. In the present study, a finite difference model was built to investigate stress evolutions around the entry, and true triaxial tests were carried out at the laboratory to explore entry wall stabilities under different mining conditions. The modeling and experimental results indicated that a wide coal pillar was favorable for entry stabilities, but oversize pillars caused a serious waste of coal resources. As the width of the entry wall decreased, the integrated vertical stress, induced by two adjacent mining panels, coupled with each other and experienced an increase on the entry wall, which inevitably weakened the stability of the entry. Therefore, mining with coal pillars always involves a tradeoff between economy and safety. To address this problem, an innovative non-pillar mining technique by optimizing the entry surrounding structures was proposed. Numerical simulation showed that the deformation of the entry roof decreased by approximately 66% after adopting the new approach, compared with that using the conventional mining method. Field monitoring indicated that the stress condition of the entry was significantly improved and the average roof pressure decreased by appropriately 60.33% after adopting the new technique. This work provides an economical and effective approach to achieve sustainable exploitation of underground coal resources.
Highlights
Coal is among the most important foundational energies, accounting for approximately 30% of the total energy consumption around the world [1,2]
Wang et al [12] proposed an approach to simulate the static and dynamic behaviors of the coal pillar. They concluded that the width-to-height (W/H) ratio of the coal pillar was important in affecting entry wall stabilities
In China, coal provides most of the energy for the development of economy and industrialization
Summary
Coal is among the most important foundational energies, accounting for approximately 30% of the total energy consumption around the world [1,2]. Basarir et al [5] predicted the stresses around the entry using empirical and numerical analysis of different mining methods (the fully mechanized traditional longwall and longwall top coal caving methods) Such issues have been addressed in the literature [6,7,8,9,10]. Wang et al [12] proposed an approach to simulate the static and dynamic behaviors of the coal pillar They concluded that the width-to-height (W/H) ratio of the coal pillar was important in affecting entry wall stabilities. Gob-side entry retaining by filling artificial materials is a frequently used non-pillar mining method to optimize sustainable mining In this method, the former entry is artificially retained as the tailgate for the mining panel by using pigsties, paste-like backfill material, high-water packing material, and other fill materials. The applicative effects indicate that the proposed approach is effective and has broad application prospects in sustainable mining of underground coal resources
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