Discrete element simulation of mechanical properties of shale with different bedding inclinations under triaxial compression
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摘要: 基于页岩室内常规三轴压缩试验结果,采用离散元程序PFC2D对不同层理倾角页岩在常规三轴压缩下进行颗粒流模拟研究,以此来分析层理倾角及围压对页岩力学特性的影响。研究结果表明:(1)页岩的峰值强度、粘聚力随层理倾角的增加整体呈“U”形变化,其中峰值强度在不同围压下的变化趋势有所区别;内摩擦角随层理倾角的增大呈非线性变化。(2)不同层理倾角页岩破坏模式不尽相同,β = 30°~45°试样易发生沿层理的剪切破坏,β = 0°~15°与β =60°~90°试样易发生共轭剪切破坏。(3)同一层理倾角试样最终破坏时的微裂纹总数随着围压的升高有所增加;在同一围压下,试样最终破坏时的微裂纹数目随着层理倾角的增加呈现先减少后增多的趋势。(4)同一层理倾角页岩的脆性随围压的增长整体呈下降趋势;低围压情况下,页岩脆性随层理倾角的增加呈两端大中间小的规律。Abstract: Based on experimental results of shale specimens under triaxial compression, PFC2D was used to simulate the mechanical properties of shale with different bedding inclinations under triaxial compression. The influence of bedding inclinations and confining pressure on shale mechanical properties is analyzed. The results reveal that: (1) With the increase of bedding inclination, the peak strength and cohesion of shale all display "U"-type variation, but the trend of peak strength is different under different confining pressures; the internal friction angle varied nonlinearly with the bedding inclination increases. (2) The failure modes of shale with different bedding inclinations are different. Specimens with β=30°~45° are prone to shear failure along the bedding, while Specimens with β=0°~15° and β=60°~90° are prone to conjugate shear failure. (3) At the same bedding inclination, the number of microcracks at the final failure of the specimen increases with the increases of confining pressure. Under the same confining pressure, the number of microcracks in the final failure of the specimen decreases first and then increases with the increases of bedding inclination. (4) With the increases of confining pressure, the brittleness of shale with the same bedding angle decreases as a whole. Under low confining pressure, shale brittleness is larger at both ends and smaller in the middle with the increase of bedding inclinations.
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Key words:
- shale /
- bedding inclinations /
- failure mode /
- brittleness index /
- discrete element simulation
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