煤岩体结构组分特性及应力损伤机制研究

    Structural components and stress damage mechanism of coal and rock mass

    • 摘要: 为研究静态应力条件下的煤岩体矿物组分与裂隙产状在其损伤破坏历程中的分布规律和发育机制,综合运用X射线衍射仪(XRD)和电子显微镜(SEM)探究煤岩体内固体骨架的矿物组分和表面裂隙形态,利用离散节理网络模型(DFN)构建可视化“块体-合成体”三维对照模型,并对比煤岩块体“载荷-位移”曲线完成合成体单轴压缩模拟分析。结果表明:因煤层和围岩体试样矿物组分以高岭土、石英为主且随衍射角度变化组分含量不同,表体裂隙形态排列复杂且附着天然缺陷(孔洞、裂隙),表明沉积作用形成的煤岩体具有非均质和多向异性特征;煤岩实体在单轴压力作用时宏观应力行为均历经“压密-弹性-塑性-破坏”4个阶段;将合成体内随机分布、大小各异的盘状裂隙依据相互交叉、联通规模,划分为Ⅰ单一型、Ⅱ切块型和Ⅲ贯穿型3类,单轴压缩作用初期Ⅰ型裂隙通过减小自身孔隙容积、密度或间距度过煤岩体受力压密阶段,块体塑性区呈现大范围的单一裂隙剪切劣化;Ⅱ型裂隙内含三角、四边和多边裂隙随应力作用相互挤压、交叉摩擦发生块间剪切滑移进入弹性阶段并维护自身结构稳定;随压应力继续增大,Ⅲ型裂隙互相贯通、连接后发生大范围张拉损伤并进入不可恢复的塑性段,最终导致块体破坏失稳。

       

      Abstract: In order to study the distribution law and development mechanism of coal and rock mineral composition and fracture occurrence in its damage and failure process under static stress conditions, X-ray diffractometer(XRD) and electron microscope (SEM) are used to explore coal and rock mass. The mineral composition and surface fracture morphology of the solid skeleton are used to construct a visualized “block-composite” three-dimensional fracture structure using the discrete joint network model (DFN), and to compare the “load-displacement” curve of the coal block to complete the uniaxial compression of the composite simulation analysis. The results of the study show that the mineral components of the coal seam and surrounding rock samples are mainly kaolinite and quartz, and the content of the components of the diffraction angle changes are different. In addition, the surface body’s fissures are complex in arrangement and attached to natural defects(holes, cavities, cracks), indicating that the coal and rock mass formed by sedimentation has the characteristics of heterogeneity and multi-anisotropy; the macroscopic stress behavior of coal and rock entities under uniaxial compression goes through the four stages of “compaction-elasticity-plasticity-failure”; the randomly distributed disc-shaped fissures of various sizes in the composite body are divided into three types: single type, block type and penetration type according to the mutual intersection and interconnection scale. TypeⅠfractures reduce the pore volume at the initial stage of uniaxial compression. Over the compressed section of coal and rock mass, the block plastic zone presents a wide range of shear degradation; the type Ⅱ fracture contains triangular, quadrilateral and multilateral fractures which are squeezed by each other with the action of stress and cross friction, resulting in interblock shear slip to enter the elastic stage and maintain its structural stability; when the type III cracks are connected to each other and cause extensive tensile damage, they enter the unrecoverable plastic section, which will eventually lead to the failure of the block.

       

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