Mechanical properties of oil shale-coal composite samples
Mechanical properties of oil shale-coal composite samples
复制标题
油页岩-煤复合样品的力学性能
DOI：
10.1016/j.ijrmms.2019.104120
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发表时间：
2019-11-01
影响因子：
7.2
通讯作者：
Zhao, Zenghui
中科院分区：
文献类型：
--
作者：
Chen, Shaojie;Yin, Dawei;Zhao, Zenghui
本研究对具有高强低弹性模量特征的煤与油页岩复合试样进行了单轴压缩试验。通过声发射（AE）装置和数字摄像机监测其破裂和破坏扩展过程。分析了复合材料试样的强度、宏观破坏起始（MFI）和破坏特征。煤与油页岩力学性能的差异影响了界面附近的应力状态，导致煤的强度增大，油页岩的强度减小。复合试样的强度特征主要取决于远离界面的煤的强度σ (C)，受煤的原始缺陷和与油页岩的相互作用的影响。油页岩的大变形减少了煤中的损伤积累，相对完整的复合试样强度大于σ (C)；相比之下，煤原缺陷较多的复合试样强度较低，且小于σ (C)。MFI发生在煤体内部，在能量指数峰值信号出现的同时，引起应力的阶梯式变化，代表复合试样宏观破坏的开始。MFI模型包括煤在界面附近的拉伸断裂、煤的原始裂纹的起裂和扩展以及煤的原始裂纹之间的表面剥落。煤体局部的抛射或表面剥落破坏诱发其周边部分的链式破坏，形成大面积的抛射或表面剥落破坏带。最后，煤沿原裂隙面表现为劈裂抛射破坏或剪切破坏。油页岩破坏主要表现为煤中裂纹扩展引起的拉伸破坏或混合破坏。
In this study, uniaxial compression tests were conducted on the composite samples of coal and oil shale characterised by high strength and low elastic modulus. Their fracturing and failure propagation processes were monitored by an acoustic emission (AE) device and a digital video camera. The strength, macro-failure initiation (MFI) and failure characteristics of composite samples are analysed. Differences in mechanical properties between the coal and oil shale influence the stress states near the interface area, resulting in strength increasing in the coal and strength decreasing in the oil shale. Strength characteristics of composite samples mainly depend on the strength sigma(C) of the coal far away from the interface, which is influenced by the coal's original defects and interactions with the oil shale. The large deformation of oil shale reduces the damage accumulation in the coal and the strengths of relatively intact composite samples are greater than sigma(C); in contrast, the strengths of composite samples with more coal's original defects are low and less than sigma(C). MFI occurs within the coal, causing a step-wise stress change accompanying the peak signal of the energy index and representing the beginning of macro-failure in composite samples. MFI models include the tensile fractures of coal near the interface, initiation and propagation of coal's original cracks, and surface spalling between coal's original cracks. The local ejection or surface spalling failure in the coal induces the chain destruction of its peripheral parts to form a large ejection or surface spalling failure zone. Finally, the coal displays the splitting ejection failure or shear failure along the original crack surface. The oil shale is destroyed through the tensile failure or mixed failure by crack propagation in the coal.