Wang Xu, Yin Shangxian, Lian Huiqing, Cao Min, Hou Enke, Xia Xiangxue, Yi Sihai, Yan Tao, Li Qixing, Wang Haorui
College of Geology and Environment, Xi'an University of Science and Technology, Xi'an, 710054, Shannxi, China.
Hebei State Key Laboratory of Mine Disaster Prevention, North China Institute of Science and Technology, Beijing, 101601, China.
Sci Rep. 2025 Aug 12;15(1):29478. doi: 10.1038/s41598-025-11176-7.
The softening and instability of the coal pillar caused by water immersion is the primary factor contributing to water inrush in the goaf of the same layer. Similarly, the softening and instability of underground reservoir dam bodies due to water immersion is a critical factor leading to reservoir water failure and dam breakage. Investigating the dynamic process of coal pillar softening and instability under water immersion conditions is of paramount importance for the prevention and control of mine water hazards in mining areas and the safety assessment of underground reservoirs. This study uses the mining of the A ore strip as an engineering background, conducts theoretical analyses and laboratory tests on coal pillars subjected to varying soaking durations, and examines the macroscopic and microscopic damage and deterioration processes of coal pillars under soaking conditions from the perspectives of mechanical properties, hydrochemical characteristics, and microstructural characterization. The experimental results indicate that within 0 to 40 days of soaking, the uniaxial compressive strength of the coal pillar decreases by 50%, the pH value of the solution shifts from weakly acidic to weakly alkaline, multiple ion concentrations undergo significant changes, mineral compositions alter, and porosity exhibits a pronounced changing trend. Based on these research findings, this paper explores the physicochemical coupling mechanism of internal structural evolution and damage deterioration in soaked coal pillars, elucidating the entire process of damage-deterioration-instability. The dynamic process of water-immersed coal pillars was studied and visualized using similar materials with water-blocking additives, revealing their spatiotemporal evolution laws. Through mechanical derivations and laboratory test results, this paper identifies the key factor influencing the instability of the overlying rock mass above the coal pillar roof, termed the "effective support width," and investigates the mechanical deterioration mechanisms of water-immersed coal pillars. Finally, based on theoretical research and indoor experiments, considering the dual effects of stress and water pressure, the calculation formula for the effective support width of water-immersed coal pillars was derived, clarifying the evolution mechanism of "damage-deterioration-instability" in the overburden rock mass above the coal pillar roof. This study discusses the dynamic process of coal pillar softening-instability under water immersion conditions in goaf areas, which holds significant implications for the retention of waterproof coal pillars in coal mines, safe mining practices, and the protection and recycling of coal pillars. Additionally, research into the damage-deterioration-instability of coal pillars provides valuable guidance for the construction of underground reservoirs and the determination of appropriate widths for coal pillar dam bodies.
煤柱浸水软化失稳是造成同层采空区突水的主要因素。同样，地下水库坝体浸水软化失稳是导致水库溃坝失事的关键因素。研究煤柱在浸水条件下的软化失稳动态过程，对于矿区矿井水害防治及地下水库安全评价具有重要意义。本研究以A矿带开采为工程背景，对不同浸泡时间的煤柱进行理论分析和室内试验，从力学性能、水化学特征及微观结构表征等方面研究煤柱在浸泡条件下的宏观与微观损伤劣化过程。试验结果表明，浸泡0～40 d内，煤柱单轴抗压强度降低50%，溶液pH值由弱酸性变为弱碱性，多种离子浓度发生显著变化，矿物成分改变，孔隙率呈现明显变化趋势。基于这些研究成果，本文探讨了浸水煤柱内部结构演化与损伤劣化的物理化学耦合机制，阐明了损伤—劣化—失稳的全过程。采用含止水添加剂的相似材料对浸水煤柱动态过程进行研究并可视化，揭示其时空演化规律。通过力学推导和室内试验结果，确定了影响煤柱顶板上方覆岩失稳的关键因素“有效支撑宽度”，并研究了浸水煤柱的力学劣化机制。最后，基于理论研究和室内试验，考虑应力和水压双重作用，推导了浸水煤柱有效支撑宽度计算公式，阐明了煤柱顶板上方覆岩“损伤—劣化—失稳”演化机制。本研究探讨了采空区煤柱在浸水条件下的软化失稳动态过程，对煤矿防水煤柱留设、安全开采及煤柱保护与回收具有重要意义。此外，煤柱损伤—劣化—失稳研究为地下水库建设及煤柱坝体合理宽度确定提供了有益指导。
