Experimental and numerical study of seepage-induced suffusion under K_0 stress state

Abstract

Suffusion in gap-graded soil involves selective erosion of fine particles through the pores formed by coarse particles under seepage forces. As the fines content (FC) decreases, the hydraulic and mechanical behavior of the soil will change, posing a huge threat to engineering safety. In this study, we first conduct a series of experimental tests of suffusion by using gap-graded soils and then analyze the evolution process of suffusion and the effect of the hydraulic gradient. Subsequently, according to the physical model, a discrete element method (DEM) numerical model with dynamic fluid mesh (DFM) is developed to extend the experimental study to the pore scale. Our results reveal the migration process of fines and the formation of erosion zones. A parametric study is then conducted to investigate the effect of the hydraulic gradient, FC, and K _0 pressure (which limits the lateral displacement of the sample and applies vertical pressure) on eroded weight. The results show that the eroded weight increases with the increase of the hydraulic gradient and FC but decreases with the increase of K _0 pressure. 目的 目前,潜蚀过程并不能被直接观察到。本研究期望采用透明仪器直接观察潜蚀的演化过程,探讨 K 0应力状态下间断级配土的潜蚀过程。 创新点 1. 研制出一个透明潜蚀仪器,可直接观测间断级配土的潜蚀过程;2. 建立数值模型,扩展试验参数,在颗粒尺度上解释潜蚀规律。 方法 1. 采用透明的潜蚀仪器,直接观测间断级配土的潜蚀过程,并记录潜蚀质量;2. 通过离散元数值模拟的方法,在颗粒尺度上揭示颗粒的迁移规律。 结论 1. 随着侵蚀的进行,试样内部形成侵蚀带并逐渐扩大;从力链分析可知,细颗粒在水流作用下逐渐堆积在粗颗粒形成的孔隙中,并被粗颗粒堵塞。2. 当侵蚀和阻塞区形成时,流速也逐渐局部化;在侵蚀区,孔隙度增大,流速普遍较快,但在阻塞区,流速较慢。3. 参数分析表明,最终潜蚀重量与水力梯度呈正相关关系,且潜蚀重量随 K 0压力的增大而减小;随着细粉含量的增加,潜蚀重量增加。