Impacts of intensive seepage flow on suffusion development in cohesionless soil: Insight from a theoretical model

Intensive seepage widely occurs due to seepage area constriction and local soil grading coarsening, which will mutually accelerate the suffusion process with greater particle loss and rapid soil structure changes. However, less research has focused on the quantitative impacts of the various intensive seepage degrees and locations on suffusion. This paper uses a verified one-dimensional model to theoretically simulate these impacts by considering two mechanisms: seepage area constriction and local soil grading coarsening. These two mechanisms are realized with gradual constricted seepage areas formed by external boundaries and coarsened soil grading of a specific layer with higher permeability. The results indicate that the two mechanisms can significantly accelerate the particle loss rate in suffusion. The acceleration is nonlinear, with the increasing proportion of the particle loss being much larger than the constriction rate. The outlet constriction causes a more extensive increase in particle movement than the midlayer constriction in the whole soil column, with the particle loss increasing by many times in most layers under the 50% constriction. Local soil grading coarsening promotes particle loss in the upstream layers. The midlayer coarsening causes a greater violence of suffusion than the outlet coarsening by serving as another outlet for particle loss. Midlayer coarsening may lead to stronger particle movement and a severalfold soil permeability increase. Intensive seepage can further promote heterogeneous development and the upward erosion of the suffusion process and then contribute to the formation of preferential paths. (C) 2022 Elsevier Ltd. All rights reserved.