不同强度比煤岩组合体力学特性及破断演化分析

    Mechanical properties and fracture evolution laws of coal-rock composites with different strength ratios

    • 摘要: 为研究煤炭开采过程中煤岩体的稳定性及其破裂演化规律,采用水泥、石膏、河砂等原材料,制备不同强度比的相似材料煤样、岩样及煤岩组合体试样。基于单轴压缩试验和数字散斑(DIC)技术,系统分析煤样、岩样及煤岩组合体的力学特性、破坏模式及破裂演化全过程。研究结果表明:煤岩组合体的峰值强度与弹性模量受煤样与岩样强度比的影响显著,且二者均介于单一煤样与对应岩样之间,即大于煤样的峰值强度和弹性模量,小于相应岩样的峰值强度和弹性模量。其中,煤岩组合体中岩样部分强度越高,组合体相较于单一煤样的强度提升幅度越大,且组合体强度与加载受力面的设置密切相关,而组合体的弹性模量整体更接近单一岩样的弹性模量。此外,煤岩组合体的破坏模式受强度比影响较小,破坏主要集中于煤体部分:当煤体部分直接承受荷载时,煤体以剪切−拉伸复合型破坏为主,且裂纹极少扩展至岩样部分;当岩样部分直接承受荷载时,煤体发生剪切型破坏,且裂纹均从煤体部分出发,经煤岩交界面中部竖直向上扩展至岩样部分。

       

      Abstract: To study the stability and fracture evolution law of coal and rock masses during coal mining, raw materials such as cement, gypsum, and river sand were used to prepare similar material coal samples, rock samples, and coal-rock composite samples with different strength ratios. Based on uniaxial compression tests and digital image correlation (DIC) technology, the mechanical properties, failure modes, and the entire fracture evolution process of coal samples, rock samples, and coal-rock composites were systematically analyzed. The research results show that the peak strength and elastic modulus of coal-rock composites are significantly affected by the strength ratio of coal samples to rock samples, and both are between those of single coal samples and corresponding rock samples, that is, greater than the peak strength and elastic modulus of coal samples, and less than the peak strength and elastic modulus of corresponding rock samples. Among them, the higher the strength of the rock sample part in the coal-rock composite, the greater the strength improvement range of the composite compared with the single coal sample, and the strength of the composite is closely related to the setting of the loading surface; while the elastic modulus of the composite is overall closer to that of the single rock sample. In addition, the failure mode of coal-rock composite is less affected by the strength ratio, and the failure is mainly concentrated in the coal part: when the coal part directly bears the load, the coal part is mainly dominated by shear-tension composite failure, and cracks rarely extend to the rock part; when the rock part directly bears the load, the coal part undergoes shear failure, and all cracks start from the coal part and extend vertically upward to the rock part through the middle position of the coal-rock interface.

       

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