理想胶结砂土力学特性及剪切带形成的离散元分析

Mechanical behavior and shear band formation in idealized cemented sands by DEM

根据近期胶结铝棒接触力学特性的实测结果,提炼出用于模拟胶结砂土粒间胶结作用的胶结接触模型,并将该模型引入二维离散元商业软件PFC2D。通过对不同胶结强度和不同围压下胶结砂土的平面应变双轴压缩试验的离散元模拟,分析了理想胶结砂土的宏观力学特性及其剪切带的形成规律。结果表明:相比同一孔隙比的无胶结试样,胶结试样具有更高的峰值强度、显著的应变软化和剪胀现象以及明显的剪切带,宏观力学特性与其胶结接触微观力学机理密切相关,模拟结果与已有室内试验结果具有规律上的一致性;由胶结试样内部的微观信息统计可知,胶结试样剪切带的形成一般在其峰值强度之后,且剪切带的形成是试样变形、胶结破坏、孔隙比、平均纯转动率和位移场等微观参量局部化的综合表现。

Focus is placed on the mechanical behavior and shear band formation in idealized cemented sands by a series of DEM biaxial compression tests involving different bond strengths and confining pressures. The DEM software PFC2D is applied with user-defined contact model, which is resulted from the mechanical tests on the bonded granules idealized by two glued aluminum rods. The results show that the cemented sands have a higher strength and more significant post-peak softening and dilatancy than the reconstituted sands, and that the simulation is consistent with the laboratory tests and closely associated with the micro bonded contact mechanism. In addition, the shear bands in the cemented sands form with the simultaneous localization of micro parameters, such as deformed specimens, void ratio, averaged pure rotation rate （APR）, displacement field and distribution of bond breakage.