Permeability property variation in sandy soil induced by suffusion via a horizontal seepage laboratory test

Suffusion is a typical kind of internal erosion that changes the permeability property of soil without destroying its structure. A horizontal laboratory test was conducted to analyze the permeability property variation in sandy soil caused by suffusion, and the content of fine sand ( R f ) varied from 5 to 25%. Water-level along the seepage path is monitored, and the average hydraulic conductivity of the whole experimental soil ( k av ) and hydraulic conductivity between two adjacent monitoring tubes ( k ij ) were obtained. The suffusion process experienced diffuse, strong and gentle-migration phases temporally according the variation tendency in k av . The rate of change in k av ( R av ) enhanced after suffusion, and the critical value of R f resulted in the largest variation in R av was 11.8%, and this conclusion was verified by a discrete element method, in which the corresponding value was 12.2%. According to the variation in R f along the seepage path, three areas were divided as the runoff, transited and accumulated areas spatially. Moreover, values of the rate of change in k ij ( R ij ) in the runoff and the accumulated areas were much larger than that in the transited area, which were resulted from loss of fine sand, rebound of water-level and comprehensive effect of migrated and accumulated fine sand.