基于不规则颗粒的砾岩力学性能数值模拟研究

砾岩非均质性强,力学性质复杂。本文基于离散元方法,使用三维激光扫描技术获取了真实砾石的颗粒形态,建立了含不同粒径颗粒的砾岩三维数值模型。基于此数值模型开展单轴抗压模拟实验,将实验结果与均质数值岩心对比,分析了砾岩破坏形式和规律,讨论了颗粒粒径大小和颗粒形态对砾岩力学性质的影响。结果表明:在加载过程中,由于砾石颗粒的阻碍,裂缝需绕过砾石颗粒逐步贯通,从而导致岩样的位移和破坏形式较为复杂,没有形成与均质岩心类似的剪切带。在加载初期裂纹数目少、增加缓慢,在应力峰值附近裂纹数量迅速增加,岩样瞬间破坏,表现出较为明显的“鼓涨”效应。砾石颗粒粒径对砾岩的破坏机理和形式影响不明显,但随着粒径的增加,砾岩单轴抗压强度和弹性模量降低。相对于圆形颗粒,基于真实砾石颗粒形态的数值模型,能够模拟砾石间的摩擦力,拥有更高的强度,能更好的反应砾岩力学性质。

Numerical simulation for mechanical properties of conglomerate based on irregular particles

Conglomerate has strong heterogeneity and complex mechanical properties. In this paper, 3D laser scanning technology obtained the particle morphology of real gravel. Based on discrete element method (DEM), a 3D numerical model of conglomerate with different particle sizes is established. Based on the numerical model, uniaxial compression simulation experiments were carried out, and the experimental results were compared with the homogeneous numerical cores. The failure modes and laws of conglomerate were analyzed, and the effects of particle size and shape on mechanical properties of conglomerate were discussed. The results show that in the loading process, cracks need to bypass gravel particles gradually through. Therefore, the displacement and failure modes of rock samples are more complex, and no shear zone similar to homogeneous core is formed. At the initial stage of loading, the number of cracks is small and increases slowly. But near the stress peak, the number of cracks increases rapidly, and the rock sample is destroyed instantly, showing an obvious "bulge" effect. The effect of gravel particle size on the failure mechanism and form of conglomerate is not obvious, but with the increase of gravel particle size, the uniaxial compressive strength and elastic modulus of conglomerate decrease. Compared with the round particles, the numerical model based on the real gravel particle shape can simulate the friction between gravel, has higher strength, and can better reflect the mechanical properties of conglomerate.