针对具有初始各向异性的间断级配砂土细粒潜蚀问题,引入可以考虑颗粒投影面积影响的Ganser拖曳力计算模型,实现非球形颗粒的计算流体动力学(computational fluid dynamics,简称CFD)和离散元(discrete element method,简称DEM)的双相耦合.通过与单颗粒下沉试验的对比,验证了该数值方法在解决异形颗粒与流体相互作用时的适用性.在此基础上,生成具有不同沉积方向和不同细粒含量的初始各向异性试样,模拟向上渗流潜蚀试验,并在试验中监测细粒流失量、强弱力链组成以及颗粒组构变化等宏微观特性,研究不同充填状态下(欠填充和过填充)不同组构各向异性土体渗流潜蚀特征.之后,对受潜蚀前后的试样进行了排水三轴试验,探究渗流对土体强度弱化的影响.结果表明,过填充试样质量损失随着颗粒沉积角度的增大而增大,而欠填充试样质量损失随沉积角度先增大后减小;欠填充试样细粒损失主要来源于低连通性细颗粒,而对于过填充试样,潜蚀则会导致低连通性和高连通性细颗粒数量同时减小.此外,三轴试验表明,潜蚀致土体峰值强度发生显著弱化,且峰值强度随沉积角度的变化也会受到土体充填状态的影响.
Computational fluid dynamics-discrete element fluidsolid coupling analysis on suffusion in anisotropic sandy soils
For the problem of suffosion in gap-graded sand with initial anisotropy,the Ganser drag force model,which can take into account the effect of the projected area of particles,is introduced to achieve a two-phase coupling of computational fluid dynamics(CFD)and discrete elements method(DEM)for non-spherical particles.The applicability of the numerical method in solving the interaction between the non-spherical particles and fluid is verified by comparing with single particle settlement tests.On this basis,specimens with different bedding orientations and fine contents are further generated to simulate upward seepage suffosion tests,during which both macroscopic and microscopic properties,such as the fine loss,composition of strong and weak force chains,and changes in grain fabric,are monitored to explore the seepage suffosion characteristics of anisotropic soils with various fabrics under different filling states(underfilled and overfilled).Drained triaxial tests are carried out on specimens before and after erosion to investigate the effect of seepage on the weakening of soil strength.The results show that the mass loss of the overfilled specimens increases with increasing bedding angle,while the mass loss of the underfilled specimens firstly increases and then decreases with the bedding angle.The loss of fines in the underfilled specimens is mainly due to the low connectivity fines,whereas for the overfilled specimens,suffosion leads to a simultaneous reduction in the number of both low and high connectivity fines.In addition,the triaxial tests show that suffusion causes a signifiicant weakening of the peak strength of the soil,and the change in peak strength with the bedding angle is also influenced by the soil filling state.
CFD-DEMsuffosionnon-spherical particlesdrag force modelanisotropymicroscopic fabric
国家科技期刊平台
NSTL
万方数据
维普
