A novel vertical stress-controlled apparatus for studying suffusion along horizontal seepage through soils

In this study, a novel apparatus was developed for the study of horizontal suffusion behavior of compacted soils under vertical stress. The apparatus consists of a permeameter chamber to accommodate specimen preparation and testing, a pressurized water supply system to generate horizontal seepage flow, a vertical loading system to apply and maintain the vertical stress onto the specimen, a pore water pressure measuring system and a soil–water collection system both to capture the characteristics of the suffusion. The apparatus is featured with a tailor-made flexible pressure bladder for vertical stress control and a modified vacuumizing method for specimen saturation. It has been verified to well perform during the horizontal suffusion, in terms of the specimen uniformity and repeatability of test results. Preliminary tests with this apparatus have been carried out to investigate the suffusion behavior of a gap-graded cohesionless soil. It can be found that suffusion can heterogenize the soil specimen along the seepage direction and that the level of vertical stress significantly affects the horizontal suffusion, such as the initiation and failure hydraulic gradient for suffusion as well as accumulated eroded weight.