Suffusion erosion, characterized as the selective detachment and transportation of finer particles by seepage flow, is hazardous to the stability and serviceability of geotechnical structures. The removal of finer particles deteriorates the structure and fabric of the soil, leading to the degradation of its mechanical properties. Studies into the effects of suffusion on mechanical behavior have so far produced disparate results depending on the pre-erosion relative density of the specimens tested. To investigate this issue, small cyclic and monotonic loading tests were performed on intact and eroded gap-graded silty sand specimens in three dispersed density states, using a triaxial cell modified for the purpose of erosion. The variation of Young's modulus showed an inverse relationship with the pre-erosion density of the specimen, as the small strain stiffness decreased in the dense cases and increased in the loose cases. Conversely, Poisson's ratio increased in value as suffusion progressed regardless of the initial density of the specimens. In the contractive phase of monotonic loading, the densification of the coarse soil skeleton by the downward seepage flow resulted in a decrease in contractiveness and an increase in secant stiffness. In the dilative phase, the increase in porosity by the erosion of finer particles reduced the dilatancy and peak strength of the specimens. The results suggest that the pre-suffusion density determines the primary locus of affected mechanical behavior in triaxial compression, which shifts from the contractive phase to the dilative phase with the increase in pre-suffusion density. The critical state strength, inferred using stress–dilatancy theory, was largely unaffected by the erosion of finer particles. As the results indicate, pre-erosion density may be of practical significance in assessing the vulnerability to deterioration and collapse of geotechnical formations and structures subjected to suffusion erosion.

渗流侵蚀是指渗流对细小颗粒的选择性分离和输送，对岩土结构的稳定性和可使用性是有害的。去除更细的颗粒会破坏土壤的结构和结构，导致其机械性能下降。迄今为止，关于渗流对机械性能影响的研究已经产生了不同的结果，具体取决于测试样品的预侵蚀相对密度。为了研究这个问题，使用为侵蚀目的而修改的三轴单元，对三种分散密度状态的完整和侵蚀的间隙级配粉砂试样进行了小循环和单调加载试验。杨氏模量的变化与试样的预冲蚀密度呈反比关系，因为小应变刚度在密集情况下降低，在松散情况下增加。相反，泊松比值随着浸液的进行而增加，而与样本的初始密度无关。在单调加载的收缩阶段，向下渗流使粗土骨架致密化，导致收缩性降低，割线刚度增加。在膨胀阶段，由于细颗粒的侵蚀而增加的孔隙率降低了试样的膨胀性和峰值强度。结果表明，预灌注密度决定了三轴压缩中受影响机械行为的主要轨迹，随着预灌注密度的增加，三轴压缩从收缩阶段转变为扩张阶段。临界状态强度，使用应力-剪胀理论推断，在很大程度上不受细颗粒侵蚀的影响。结果表明，侵蚀前的密度可能对评估遭受浸蚀的岩土地层和结构的退化和倒塌的脆弱性具有实际意义。