Research and Engineering Practice of Coupled Unloading and Supporting Technology for Rock Burst Prevention in Hard Coal Seams of the Ordos Region

Gang Han^1,2,3*Linming Dou¹Jiahao XIE^1,2,3Qian Zhao⁴Yawu Shao^1,2,3Mingming Sun^1,2,3Liang Mou^1,2,3

• ¹China University of Mining and Technology, Xuzhou, China
• ²China Coal (Ordos City) Energy Technology Co Ltd, Ordos Inner Mongolia, China
• ³China Coal Energy Research Institute Co Ltd, Xi'An, China
• ⁴China Coal Energy Company Limited, Beijing, China

Hard coal seams in the Ordos region are key geological factors triggering rock bursts. To tackle the limitations of conventional drilling methods—such as poor pressure relief, the need for high-density multi-round pressure relief, and support failure—a non-isobaric stress field model was established. A mechanical analysis was conducted to investigate how the plastic zone radius of drilling is influenced by coal seam strength and drilling diameter. A "shallow support and deep pressure relief" coupling technology for hard coal seam unloading support was proposed. An on-site 70-meter comparative industrial test was conducted, utilizing coal powder monitoring, coal cannon monitoring, stress monitoring, and surrounding rock deformation monitoring to assess the pressure relief and support effects. The key conclusions are as follows: (1) The plastic zone radius of drilling is mainly influenced by coal seam strength and drilling diameter. Higher coal seam strength leads to a smaller radius, while a larger drilling diameter increases the radius; however, the effect of growing diameter diminishes beyond a certain threshold, and simply expanding the diameter cannot continuously improve pressure relief. (2) In terms of pressure relief effect, the amount of coal powder in the expanded pressure relief zone was 3.1 times that of conventional drilling. "Coal cannon" events were concentrated in the 7–14m section of the coal wall, effectively releasing the accumulated elastic energy in the coal. After pressure relief, the peak stress of the coal was lower and recovered more slowly, achieving significant unloading of static load-concentrated areas. (3) Regarding the support effect, during and after the borehole expansion pressure relief period, the stress on the roadway roof and side anchor cables remained stable and lower than that in conventional drilling. The maximum reduction in roadway side convergence was 63%, and that in roof-floor convergence was 51%, showing better surrounding rock deformation control than conventional large-diameter drilling. (4) A comprehensive anti-burst technology and equipment system based on mechanical drilling and pressure relief was developed and successfully applied in engineering demonstrations. The research results provide a theoretical basis and practical reference for mines with similar conditions in the Ordos region.