矿井水害是煤矿开采过程中重要致灾因素之一，严重威胁着煤矿及工人的生命和财产安全。近年来老空水突水事故频发，隔水煤柱是重要的安全防范措施。老空水多为酸性，其对隔水煤柱强度的持续损伤和弱化是致灾的重要原因之一。本研究以酸性矿井水浸蚀的煤岩为研究对象，以表征浸蚀煤岩的特征规律，揭示其损伤机理，确定其长期强度为研究目的。采用三轴力学试验获取了浸蚀煤岩的宏观力学特征，PFC数值模拟反演获取了力学损伤细观特征；扫描电镜（SEM）、计算机断层扫描（CT）、¹H核磁共振（NMR）获取了微观结构变化特征；运用X射线衍射（XRD）、红外线光谱（FIRT）测试以及气蚀理论，从化学损伤和物理损伤两个方面揭示了煤岩的损伤机理；通过煤岩三轴蠕变试验和长期强度理论确定了浸蚀煤岩的长期强度，并在四台煤矿进行了工程应用。取得了以下研究成果和结论。

（1）建立了浸蚀煤岩的宏观力学特征与溶液酸性（pH）和浸蚀时间（t）两个影响因子的映射关系。浸蚀煤岩的强度与影响因子的强化呈负相关，压密阶段最大应力持续减小，线弹性阶段有效抗压区间持续较小，微裂隙产生的阈值逐渐降低，煤岩的强度持续弱化，最大减小58.51%。相比之下，酸性影响因子对煤岩强度的弱化更显著。基于能量守恒定律，首次建立了化学能对煤岩浸蚀损伤的本构模型。

（2）揭示了浸蚀煤岩的破坏机制和细观特征。随着影响因子的强化，内聚力和接触抗拉强度累计损伤在逐步增加，但增幅在逐步减小；接触力骨架高受力区，裂缝区和低受力区箱体呈现减小趋势；颗粒移动速度呈减小趋势，移动速度箱体区间越来越小；微裂缝的发育均呈增大趋势；颗粒位移均趋向减小，不同浸蚀酸度减小的幅度有差异，时间因子对颗粒位移的影响稍弱一些。

（3）表征了浸蚀煤岩的微观结构变化特征。随着影响因子的强化，面孔率成增大趋势，在浸蚀初期，酸性因子对面孔率的影响比较大。随时间因子的增大，面孔率增长呈现出加速溶蚀、稳定溶蚀、减速溶蚀的阶段律动性。分形维数D呈增大，平面孔隙结构变趋向杂乱，在pH3.8处呈现明显界线。孔隙三维分布特征表明，在酸度较小的时候，较大孔隙容易渗透的地方有明显的扩孔作用。随着酸度增强，其面孔率整体增大，面孔率在0.12%以下的，增大幅度很小，在0.3%以上的，浸蚀后面孔率几乎扩大了一倍多，部分面孔率发生减小的现象。浸蚀煤岩的孔隙度、渗透率、T₂截止值、可流动体饱和度均呈现减小趋势，煤岩的微孔径比例减小、过渡孔、中孔、大孔隙的比例均在增大。

（4）揭示了浸蚀煤岩的损伤机理。煤岩微晶体的层间间距（d₀₀₂）、平均高度L_c、微晶体的层数N均呈减小趋势；煤微晶的平均直径L_a呈增大趋势。(d₀₀₂ )值对浸蚀煤岩宏观强度影响的重要分界点为0.35nm，影响因子在pH3.8处。煤有机质的芳香结构中的芳香氢率（）、芳香碳率（）、相对丰度指标（I）均逐渐降低，芳香核的缩合度（DOC）呈增大趋势；脂肪族中的A(CH2)/A(CH3)降低，支链烷基的脱离引起脂肪链缩短；含氧结构中'C'增大，煤中富含C=O基团的醇、酚和醚基团转化为羰基、羟醛和羧基。

（5）确定了浸蚀煤岩的长期强度。随着酸性因子的增强，煤岩的长期强度呈减小趋势，最大弱化为原煤长期强度的38.40%。时间因子对煤岩长期强度的弱化过程为时间积累、加快弱化、再次积累的过程。长期强度与抗压强度的关系分为两段，快速减小段从87.35%减小至80.42%；另一段减小趋势相对平稳，围绕80%附近浮动变化。pH4为明显的分界点。

（6）分析了四台煤矿隔水煤柱长期强度及稳定性。通过试验测试获得原煤和浸蚀后煤岩的强度为 36.3MP_a和19.6MP_a，长期强度分别 28.22 MP_a和15.35MP_a。随着煤岩侵蚀和垮塌，应力持续迁移，煤柱在0.19L₂处达到浸蚀煤岩的长期强度，在0.56 L₂时，整个煤柱将失稳。

Mine water damage is one of the important disaster-causing factors in the process of coal mining, which seriously threatens coal mining and the safety of people's lives and properties. In recent years, water inrush accidents have occurred frequently in old air, and water-proof coal pillars are an important safety precaution. Most of the old empty water is acidic, and its continuous damage and weakening of the strength of the water-resistant coal pillar is one of the important reasons for the disaster. In this study, the coal rock statically etched by acid mine water is taken as the research object, to characterize the characteristic law of the etched coal rock, reveal its damage mechanism, and determine its long-term strength. The macroscopic mechanical characteristics of the etched coal rock were obtained by triaxial mechanical test, and the mesoscopic characteristics of mechanical damage were obtained by PFC numerical simulation and inversion. Scanning electron microscopy (SEM), computed tomography (CT) and 1H nuclear magnetic resonance (NMR) Microstructure change characteristics; using X-ray diffraction (XRD), infrared spectroscopy (FIRT) test and cavitation theory, the damage mechanism of coal and rock was revealed from two aspects of chemical damage and physical damage; The long-term strength theory determines the long-term strength of the etched coal and has been applied in engineering in Sitai Coal Mine. The following research results and conclusions are obtained.

(1) The mapping relationship between the macro-mechanical characteristics of etched coal and the two influencing factors of solution acidity (pH) and etching time (t) was established. The overall strength of eroded coal and rock is negatively correlated with the increase of the strength of the influence factor. The maximum stress in the compaction stage continues to decrease, the effective compression range in the linear elastic stage continues to be small, the threshold for the generation of micro-cracks gradually decreases, and the strength of the coal rock continues to decrease. Weakened, with a maximum reduction of 58.51%. In contrast, the degree of damage to coal rock by acidic influence factors is more significant. Based on the law of conservation of energy, the constitutive model of chemical energy damage to coal and rock is established for the first time.

(2) The mesoscopic characteristics of mechanical damage of eroded coal and rock are revealed. With the strengthening of the influence factor, the cumulative damage of cohesion and contact tensile strength is gradually increasing, but the increase is gradually decreasing. The velocity is decreasing, and the moving speed box interval is getting smaller and smaller; the development of micro-cracks is increasing; the particle displacement tends to decrease, and the reduction range of different etching acidity is different, and the time factor affects the particle displacement. The effect is slightly weaker.

(3) The microstructure change characteristics of the etched coal rock were characterized. With the strengthening of the impact factor, the surface porosity tends to increase. In the early stage of etching, the acid factor has a greater impact on the surface porosity. With the increase of time factor, the increase of surface porosity shows the stage rhythm of accelerated dissolution, stable dissolution and deceleration dissolution. The fractal dimension D increases, and the planar pore structure tends to be chaotic, showing an obvious boundary at pH 3.8. The three-dimensional distribution characteristics of pores show that when the acidity is small, there is obvious pore expansion in the places where the larger pores are easy to penetrate. As the acidity increases, the surface porosity increases as a whole. If the surface porosity is below 0.12%, the increase is very small. If it is above 0.3%, the surface porosity has almost doubled after etching, and some surface porosity occurs. decrease phenomenon. The porosity, permeability, T2 cut-off value and flowable body saturation of eroded coal showed a decreasing trend. The proportion of micro-pore size decreased, and the proportion of transition pores, mesopores and macropores increased.

(4) The damage mechanism of eroded coal and rock is revealed. The interlayer spacing (d002), the average height Lc, and the number of layers N of the coal microcrystals all showed a decreasing trend; the average diameter La of the coal microcrystals showed an increasing trend. The important demarcation point of the influence of (d₀₀₂ ) value on the macroscopic strength of eroded coal rock is 0.3500nm, and the influence factor is at pH 3.8. The aromatic hydrogen ratio ( ), aromatic carbon ratio () and relative abundance index (I) in the aromatic structure of coal organic matter gradually decreased, and the degree of condensation (DOC) of aromatic nucleus showed an increasing trend; A(CH2 )/A(CH3) decreases, the detachment of branched alkyl groups causes the shortening of the aliphatic chain; the 'C' in the oxygen-containing structure increases, and the alcohol, phenol and ether groups rich in C=O groups in coal are converted into carbonyl, Aldol and carboxyl.

(5) The long-term strength of the etched coal rock was determined. With the increase of the acid factor, the long-term strength of coal and rock shows a decreasing trend, and the maximum weakening is 38.40% of the long-term strength of raw coal. The weakening process of the time factor to the long-term strength of coal is the process of time accumulation, accelerated weakening and re-accumulation. The relationship between long-term strength and compressive strength is divided into two sections. The rapid reduction section decreases from 87.35% to 80.42%; the other section has a relatively stable decreasing trend, which basically fluctuates around 80%. pH4 is the clear cut-off point.

(6) The long-term strength of water-resistant coal pillars in Sitai Coal Mine is analyzed. The strengths of raw coal and etched coal are 36.3Mpa and 19.6Mpa, and the long-term strengths are 28.22Mpa and 15.35Mpa, respectively. As the coal erodes and collapses, the stress continues to migrate, and the coal pillar reaches the long-term erosion of the coal rock at 0.19 L₂, and at 0.56 L₂, the entire coal pillar will be unstable.