An innovative approach to thin coal seam mining of complex geological conditions by pressure regulation

The hard rock parting contained in thin coal seams constrains the development of high-efficiency mining due to high level of equipment wear and low mining advance rate. To achieve safe and high-efficiency mining in thin coal seam with such complex geological conditions, an innovative mining approach using pressure regulation was proposed to substitute traditional deep-hole blasting technique to pre-break the coal and hence promote the flaking of hard parting during mining. Firstly, the strata pressure behaviors in the thin coal seam containing hard iron sulphide concretion parting were investigated by field monitoring and modeling study. Then, the feasibility of abutment pressure regulation via supporting force adjustment to pre-break the coal was proved by numerical experiments. The results show that the existence of hard iron sulphide concretions resulted in localized stress concentration by 30% and the profile of damage zone transforms to be radial and discontinuous. However, it does not enlarge the size of effective damage zone much. The results also reveal that the width of damage zone increases linearly with the decrease of supporting force at the logarithmic scale. This provides a theoretical guidance for the fully-mechanised thin coal seam mining face with hard rock parting. The implementation of pressure regulation in actual mining demonstrates that it can effectively enhance the mining advance rate and significantly reduce mining machine wear.