Lu H F , Wang J Z, et al. Research on resistance to permeability failure in shallow coal seam mining under unconsolidated aquifer［J］. Journal of Henan Polytechnic University（Natural Science），doi: 10.16186/j.cnki.1673-9787.2026050004

doi: 10.16186/j.cnki.1673-9787.2026050004

Received：2026-05-07

Revised：2026-07-05

Online：2026-09-29

Research on resistance to permeability failure in shallow coal seam mining under unconsolidated aquifer

Lu Haifeng^1,2, Wang Junzhe¹

(1.School of Earth and Environment, Anhui University of Science and Technology, Huainan 232001, Anhui, China；2.State Key Laboratory of Fine Exploration and Intelligent Development of Coal, Beijing, Haidian District, 221116）

Abstract: [Objective] To address the challenge of quantitatively evaluating resistance to permeability failure in shallow coal seam mining under unconsolidated aquifers, the 8201 working face of the Wobei Coal Mine was selected as the engineering background. Laboratory geotechnical tests, fluid-solid coupling numerical simulation, and groundwater dynamics analytical methods were comprehensively employed to investigate the seepage evolution behavior of mining-induced overburden fractures connecting the Fourth Aquifer (hereinafter referred to as the "No. 4 aquifer") and the highly weathered zone.[Methods] The critical hydraulic gradients of the No. 4 aquifer and the highly weathered zone were first obtained through laboratory geotechnical tests. The FLAC³D fluid-solid coupling numerical simulation was then adopted to inversely analyze the mining-induced seepage field. The distributions of actual hydraulic gradients at the base of the No. 4 aquifer and within the weathered zone during the mining process were obtained. Concurrently, an analytical model of fully penetrating confined well flow was established. The theoretical radial hydraulic gradient distribution at the water inrush channel was derived from this model. Finally, the critical and actual hydraulic gradients were compared to comprehensively evaluate the risk of permeability failure.  [Results] The critical hydraulic gradients of the No. 4 aquifer and the highly weathered zone were determined to be 1.42 and 1.62, respectively. The numerical simulation yielded maximum actual hydraulic gradients of 1.30 at the base of the No. 4 aquifer and 1.50 within the weathered zone. The groundwater dynamics analytical solution gave a maximum hydraulic gradient of 1.25 at the channel wall. The results obtained from the two methods mutually validated each other. The actual seepage driving forces across the entire field were all strictly below the critical resistance thresholds.  [Conclusion] Under the current design of the sand-control coal pillar, the risk of permeability failure and water-sand inrush at the 8201 working face was found to be extremely low. A quantitative evaluation method for permeability failure of sand-control coal pillars was established, with the comparison between critical and actual hydraulic gradients as its core. The multi-method collaborative approach enables accurate quantitative assessment and provides a reliable scientific basis for safe mining of shallow coal seams and water hazard prevention and control.

Key words:loose aquifer; sand-proof coal pillar; hydraulic gradient; seepage failure;fluid-solid coupling

CLC:TD821