煤矿地下水库的连续运行使煤柱坝面临采矿扰动和长时间的浸水,导致煤柱力学性质恶化,对大坝的稳定性构成严重威胁。为此,选取神东矿区大柳塔矿5-2煤层拟建柱坝的煤样进行了反复浸水条件下的吸水试验和三轴压缩试验,为了研究水岩作用下煤样的力学性质和声发射破坏特征以及煤样劣化的机理。结果表明:(1)随着浸水次数的增加,煤样的饱和水含量逐渐增加,但是增长率递减。(2)随着水浸次数的增加,抗压强度,凝聚力,煤样的内摩擦角逐渐减小。值得注意的是,劣化效应在抗压强度和内聚力方面更为明显,虽然内摩擦角的下降相对较小,上述三者的总恶化程度和阶段恶化程度具有明显的累积性和不均匀性。水浸时间的逐渐增加导致恶化效果的逐渐减弱。同时,围压对煤样强度劣化有一定的抑制作用。(3)与干煤样相比,一次水浸煤样的平均AE计数率显着下降,和随后的水浸泡两个,三,四次导致平均AE计数率下降很小。(4)随着水浸次数的增加,煤样中的AE累积振铃计数表现出不同程度的降低。具体来说,AE累积振铃计数的最显著减少发生在初始水浸后,随后逐渐减少。煤样的能量释放能力下降,而它们的可塑性表现出逐渐增加。(5)建立了基于水浸次数的煤样损伤模型。该模型表明,随着水浸次数的增加,煤样的损伤增加,损伤率逐渐下降并最终趋于稳定。(6)解释了水岩作用下煤的变质机理。通过反复的水浸,物理,化学,和水和煤之间的机械相互作用引起的煤样内部微观结构的变化,导致压缩强度等机械性能恶化,凝聚力,和内摩擦角,这是一个从微观到宏观的累积损伤过程。
The continuous operation of coal mine underground reservoirs exposes the coal pillar dams to mining disturbances and prolonged water immersion, resulting in the deterioration of coal pillars\' mechanical properties and posing a serious threat to the dam stability. To this end, coal samples from the proposed pillar dam in the 5-2 coal seam of Daliuta Mine in Shendong Mining Area were selected for conducting water absorption tests and triaxial compression tests under conditions of repeated water immersion, in order to
study the deterioration of the mechanical properties and acoustic emission damage characteristic of coal samples as well as the mechanism behind the deterioration of coal samples under the water-rock interaction. The results indicated that: (1) the saturated water content of coal samples exhibited a progressive increase as the water immersion times increased, but with a diminishing rate of growth. (2) As the water immersion times increased, the compressive strength, cohesive force, and internal friction angle of coal samples gradually decreased. Notably, the deterioration effect was more pronounced in compressive strength and cohesive force, while the decline in internal friction angle was relatively minor, and the total deterioration degree and the stage deterioration degree of the above three had evident cumulativity and non-uniformity. The progressive rise in water immersion times led to a gradual attenuation of the deterioration effect. Meanwhile, the confining pressure exhibited a certain inhibitory impact on the strength deterioration of coal samples. (3) Compared to the dry coal samples, the average AE count rate of coal samples subjected to a single water immersion exhibited a significant decrease, and subsequent water immersion for two, three, and four times resulted in a very minor decrease in the average AE count rate. (4) The AE cumulative ringing counts in coal samples exhibited varying degrees of reduction as water immersion times increased. Specifically, the most significant decrease in AE cumulative ringing counts occurred after the initial water immersion, followed by a gradual decrease thereafter. The energy-releasing capacity of coal samples decreased, while their plasticity exhibited a gradual increase. (5) A damage model was developed for coal samples based on the water immersion times. The model indicated that the damage to coal samples increased as the water immersion times increased, and the damage rate gradually decreased and eventually stabilized. (6) The deterioration mechanism of coals under the water-rock interaction was explained. Through repeated water immersion, the physical, chemical, and mechanical interactions between water and coal induced alterations in the internal microstructure of coal samples, resulting in the deterioration of mechanical properties such as compressive strength, cohesive force, and internal friction angle, which was a cumulative damage process from the microscopic to the macroscopic level.