粗粒土渗透变形特性的细观数值试验研究

为深入探究渗透变形对粗粒土渗透特性的影响,基于室内粗粒土渗透变形物理试验成果分析,利用颗粒流软件PFC3D对粗粒土的渗透性演化全过程进行细观数值仿真试验。数值试验研究成果表明:随着试验水头升高,试件中的细小颗粒从渗流"上游区"向"下游区"逐渐迁移、汇聚,形成渗透挤密区;渗透挤密现象的产生导致试件整体渗透系数减小;随着试验水头持续升高,渗透挤密区中的细颗粒在不断增加的渗透力作用下随水流被陆续带出,渗透系数逐渐增大。颗粒迁移导致原有孔隙增大,土骨架结构发生变化,进而导致粗粒土渗透性越来越大,最终形成渗透变形现象。细观数值试验方法可以较好地再现粗粒土的渗透变形过程。

Mesoscopic numerical tests on seepage failure characteristics of coarse grained soils

To deeply explore the influences of seepage failure on permeability feature of coarse grained soils, based on the analysis of indoor experiment results of seepage failure tests on coarse grained soil samples, the software named PFC^3D is employed to simulate the whole process of seepage failure with similar test situation. The research results show that the fine particles in the samples migrate from“upstream” to “downstream” location with the increment of water head. The fine particles are gathered at the downstream location of the seepage path in the test samples and the compaction area is formed due to seepage. The phenomenon of seepage compaction induces the decrease of permeability of the test samples. Under the action of the increasing water head, the fine particles in the compaction area migrate out of the samples with seepage water. The coefficient of permeability also increases gradually. The porosity of the test samples becomes large due to the loss of the fine particles. The skeleton structure of the soil test samples is also changed. This is the reason for the increase of permeability of the coarse grained soils due to seepage. When a larger mount of the particles are brought out of the soil samples, the phenomenon of seepage failure is then formed. It is also indicated that the mesoscopic numerical test method can recreate the process of seepage failure reasonably.