基于CFD-DEM的渗蚀研究:细粒含量与围压的影响

Research of erosion based on CFD-DEM method:The effect of fine particle content and confining pressure

为了揭示渗透水流对砂土渗蚀破坏的规律,利用流固耦合方法(CFD-DEM)建立具有应力边界的长方体砂土试样,进行了不同围压和细粒含量条件下间断级配砂土的渗蚀模拟。结果表明,1)对于高细粒含量试样,围压越高渗蚀颗粒流失量越高,但对于低细粒含量试样,围压对渗蚀的促进作用并不明显。2)当细颗粒含量较高时,细粒流失会引起力链屈曲,促使颗粒间接触力减小,并且高围压下试样力链屈曲量越多,导致细颗粒流失增多。当细粒含量较低时,细颗粒不能填满粗颗粒间的空隙,承担外力的程度也较低。围压的增大主要由粗颗粒承担,细颗粒间接触力和接触数变化不大,因此围压对砂土细颗粒在渗蚀过程中的流失影响也较小。所得结论明晰了渗透水流作用下土体细颗粒在粗颗粒形成的骨架中选择性流失的过程,对控制砂土渗蚀破坏具有借鉴作用。

In order to reveal failure mechanisms of sandy soil induced by seepage flow,a series of sand test samples were established by using discrete element method(CFD-DEM),and with different confining pressures and fines contents,the erosion simulation of discontinuous graded sand was carried out.The results show that:1)for the samples with high fines contents,the higher the confining pressure is,the higer the loss of erosion particles is,while for the samples with low fines contents,the confining pressure has a slight influence on erosion.2)when the content of fine particles is high,the loss of fine particles causes the buckling of the force chain,and the contact force between fine particles decreases.Under high confining pressure,the larger the number of the buckled force chain is,the more the loss of the fine particles is.When the content of fine particles is low,the fine particles underfill the voids between coarse particles,and the degree of bearing external force is also low,the increase of confining pressure is mainly borne by the coarse particles,resulting in little change in the contact force and contact number between the fine particles.Therefore,the confining pressure has little effect on the loss of fine particles during erosion.The conclusions accurately reveal the selective loss process of fine particles in the skeleton of coarse particles formation under the action of seepage flow and can provide reference for the control of sand erosion damage.