循环载荷作用下裂隙煤岩组合体宏细观力学行为
Macro-meso mechanical behavior of fractured coal-rock composites subjected to cyclic loading
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摘要: 为研究循环载荷作用下含相同裂隙煤岩组合体损伤劣化特征, 通过室内试验与数值模拟, 研究了煤岩比例、循环加载幅值对岩−煤−岩组合体损伤演化及宏细观破坏机制的影响。结果表明: 煤体裂隙网络主导组合体强度与破坏。在循环加卸载过程中, 应力−位移曲线呈现滞回效应, 初期小且密集, 后期大而疏松, 位移随时间正弦波动变化, 在失稳前几次循环位移整体增加。当颗粒受力大于颗粒胶结强度时, 裂纹首先萌发于煤裂隙尖端处, 之后受力集中点转移至周围颗粒, 使得裂纹呈条带发育, 多组裂纹条带与破碎区间形成贯穿裂纹带, 使试样失去其承载能力。随着组合体中煤的比例增加, 组合体强度降低、位移增大, 声发射b值减小, 发生失稳的循环次数降低。随着循环加载幅值增大, 组合体位移增大, 声发射b值减小, 对组合体劣化程度加深, 更易导致组合体试件失稳。Abstract: To study the damage and deterioration characteristics of coal-rock combinations with the same fractures under cyclic loading, experiment and numerical simulation were conducted to investigate the effects of coal-rock ratio and cyclic loading amplitude on the damage evolution and macro-micro failure mechanisms of rock-coal-rock combinations. The results show that the coal fracture network dominates the strength and failure of the combination. During the cyclic loading and unloading process, the stress-strain curve shows a hysteresis effect, which is small and dense at the initial stage and large and sparse at the later stage. The displacement changes sinusoidally with time, and the overall displacement increases in the first few cycles before instability. When the force on the particles is greater than the particle bonding strength, cracks first initiate at the tip of the coal fractures, and then the force concentration point shifts to the surrounding particles, causing the cracks to develop in a band-like manner. Multiple sets of crack bands and fracture zones coalesce through crack bands, causing the specimen to lose its load-bearing capacity. As the proportion of coal in the combination increases, the strength of the combination decreases, the displacement increases, the b value of acoustic emission decreases, and the number of cycles before instability decreases. As the cyclic loading amplitude increases, the displacement of the combination increases, the b value of acoustic emission decreases, the degree of deterioration of the combination deepens, and it is more likely to cause instability of the combination specimen.
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