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煤体内部裂隙-矿物组构模态对其力学行为的影响

Influence mechanism of fracture-mineral spatial fabric on the mechanical behavior of coal body

  • 摘要: 煤体内含有多尺度原生裂隙与充填矿物,二者空间分布的各向异性显著,相对位置关系多样,共同影响着煤体的力学性质与采动力学行为。研基于CT扫描与数字岩心技术,实现了煤样裂隙-矿物空间分布特征辨识,构建了试样尺度下煤体内部典型裂隙-矿物空间分布典型组合场景,并在此基础上进一步揭示了不同裂隙-矿物空间组合分布模式对煤体力学行为的影响机制。结果表明:(1)基于研究的有限样本分析,裂隙-矿物空间组构有平行和垂直2种典型空间位置关系。(2)裂隙与矿物的垂直间距对裂隙扩展方向影响显著,且存在一间距临界值(SCV),当间距小于SCV时,裂隙扩展沿原生裂隙发育方向向矿物边界靠拢;当间距大于SCV值时,裂隙扩展仍沿原生裂隙方向进一步延伸,矿物对裂隙扩展方向的控制作用减弱。(3)充填矿物的存在改变了试件的力学性质(抗压强度、应力应变、弹性模量),这种改变的程度仍然与SCV存在相关关系,当间距小于SCV时,试样的单轴抗压强度与间距大小呈正相关,但均低于无充填矿物时煤体的单轴抗压强度;当间距大于SCV时,试样的单轴抗压强度与间距大小无显著相关性,但均高于无充填矿物时煤体的单轴抗压强度。在此基础上根据SCV,进一步量化了4种“模态”(平行相离、平行共面、垂直相交、垂直相离)的判断依据。(4)裂隙-矿物空间组构模态控制着煤体的力学性质与行为响应,“平行共面”和“垂直相交”模态会弱化煤体强度,与无充填矿物试件相比,单轴抗压强度分别降低了8.42%和8.96%;“平行相离”和“垂直相离”模态会强化煤体强度,与无充填矿物试件相比,单轴抗压强度分别升高了7.17%和10.42%。

     

    Abstract: The coal body contains multi-scale primary cracks and filling minerals. The anisotropy of the spatial distribution of the two is significant, and the relative positional relationship is diverse, which affects the mechanical properties and mining dynamic behavior of the coal body. Based on CT scanning and digital core technology, the spatial distribution characteristics of fracture-mineral in coal samples were identified, and the typical combination scenes of typical fracture-mineral spatial distribution in coal samples were constructed. On this basis, the influence mechanism of different fracture-mineral spatial combination distribution modes on the mechanical behavior of coal was further revealed.The results indicate that:(1) Based on the limited sample analysis of this study, the fracture-mineral spatial fabric exhibits two typical spatial positional relationships: parallel and vertical.(2) The vertical spacing between fractures and minerals exerts a significant influence on the direction of fracture propagation, and there exists a Spacing Critical Value (SCV). When the spacing is less than the SCV, fracture propagation tends to approach the mineral boundary along the development direction of primary fractures. When the spacing exceeds the SCV, fracture propagation continues to extend further along the direction of primary fractures, and the mineral's control over the fracture propagation direction is weakened.(3) The presence of filled minerals alters the mechanical properties of the specimens (including uniaxial compressive strength, stress-strain behavior, and elastic modulus), and the degree of such alteration is still correlated with the SCV. When the spacing is less than the SCV, the uniaxial compressive strength of the specimens is positively correlated with the spacing, but all values are lower than that of coal without filled minerals. When the spacing is greater than the SCV, the uniaxial compressive strength of the specimens has no significant correlation with the spacing, but all values are higher than that of coal without filled minerals. On this basis, the judgment criteria for the four "modes" (Parallel Separation, Parallel Coplanar, Vertical Intersection, Vertical Separation) are further quantified according to the SCV.(4) The fracture-mineral spatial fabric mode dominates the mechanical properties and behavioral responses of coal. The "Parallel Coplanar" and "Vertical Intersection" modes weaken coal strength; compared with specimens without filled minerals, their uniaxial compressive strengths decrease by 8.42% and 8.96%, respectively. The "Parallel Separation" and "Vertical Separation" modes enhance coal strength; compared with specimens without filled minerals, their uniaxial compressive strengths increase by 7.17% and 10.42%, respectively.

     

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