Experimental evaluation of physical, mechanical, and permeability parameters of key aquiclude strata in a typical mining area of China

Abstract

Coal production safety and protection of water resources in coal mines located under aquifers requires an in-depth analysis of key aquiclude strata (KAS), including their physical, mechanical, and seepage characteristics. Based on hydrogeological conditions of thickness and buried depth of coal seam, thickness and water abundance of the aquifer, KAS thickness, etc., the experimental comprehensive testing method of mechanical and permeability parameters of KAS in the Wugou Coal Mine, China, are proposed. This paper applies state-of-the-art X-ray diffraction (XRD), scanning electron microscopy (SEM), and mechanical test methods to study mineral composition, microstructure, mechanical properties, water absorption, and softening coefficient of KAS rock samples collected from the mine under study. The comprehensive analysis of the results obtained made it possible to clarify the particular water-inrush mechanism and stability control of KAS using the revealed stress-strain-permeability dependencies of composite KAS and non-Darcy seepage behavior of post-peak fractured KAS. The model of KAS damage status with different backfill effects is established and successfully applied to the case study. Findings of this study are considered instrumental in the KAS-based prevention of water-inrush hazards and more rational exploitation of coal resources.