Impacts and applications of full-cycle floor drift on excavation and working face

摘要

To investigate the impact of full-cycle floor drifts on the production and safety of mining faces, this study aims to clarify the overlapping range of fracture zones between coal roadways and floor gas drainage drifts during excavation, as well as the stability-maintaining parameters and functional mechanisms of full-cycle floor drifts during mining. The time-varying superimposed effects of fracture zones in full-cycle floor drifts and coal roadways were analyzed, leading to the determination of the optimal layout interval between full-cycle floor drifts  (with different service lives) and coal roadways. Additionally, the optimal goaf pressure reduction coefficient was identified using the comprehensive mean difference, and the depth and width of fracture development in the mining face floor were quantified. Based on these theoretical results, numerical simulations were performed using FLAC^3D software, field tests were conducted to verify the reliability of the theoretical deductions and numerical models. The verification results indicate that when the full-cycle floor drifts in the Xin'an Coalfield is arranged 17 m below the coal seam floor and 10 m inward offset from the coal roadway, it can fully satisfy to the technical requirements of face excavation and mining. Specifically, the height and width deformations of the full-cycle floor drifts are reduced from 800–950 mm and 510–520 mm to 450–550 mm and 250–350 mm, respectively, with deformation reduction rates of 42–43% (height) and 32–50% (width). Meanwhile, temporary boreholes in the full-cycle floor drifts can effectively extract gas from the coal seam (around the open-off cut of the mining face) and goaf, reducing the gas emission rate of the working face by 0.95 m³/min and ensuring that the gas concentration in the return airflow remains stable within 0.22% during mining in thick coal zones.