Critical Physical and Hydraulic Condition for Fine Grains Migration, Deposition and Self-dredging in Seepage Erosion of Gravel Soil

Fine particle migration mechanism is the basis and key to understand the seepage erosion process of gravel soil, and it is important to study the fine view disaster-causing mechanism of rainwater erosion process of gravel soil slope. In this work, the types of movement of fine particles and the critical points of transformation during sand and gravel soil erosion are discussed, and in particular, the influencing factors and mechanisms affecting the transport of fine particles are analyzed. The results showed: under the action of hydraulic force, the overall movement state of the fine grains can generally be divided into two modes: deposition and self-dredging. The internal stability of the gravel soil and the external hydraulic conditions determine whether the fine particles are deposited or self-dredging. It is found that the particle size ratio can well describe the internal stability of sandy gravel soil, so the critical curve of fine particle deposition-filtration is established by particle size ratio and hydraulic gradient.