Impact of specimen preparation on erosion and post-erosion response of gap-graded soils

University of Melbourne, Department of Infrastructure Engineering, Melbourne, Australia

^* Corresponding author: mahdi.miri@unimelb.edu.au

Abstract

Internal erosion is a major threat to the safety and operation of water management structures. Recent failures of embankment dams reported in Australia, Canada, and the US are fresh reminders of the importance of this ongoing issue. Suffusion, the focus of this paper, is one of the main modes of internal erosion occurring in internally unstable soils. It initiates internally, continues slowly with no visible signs, and leads to complete failure if not detected early. Despite recent advances in understanding the influence of suffusion on the mechanical behaviour of internally unstable soils through laboratory investigations, the impact of sample preparation techniques on the soil response during erosion and afterwards is yet to be fully undrstood. When it comes to laboratory investigation of remoulded soils, it has been understood that soil specimens prepared by different techniques show different characteristics and soil fabrics. This research studied the influence of sample preparation methods on the erosion of non-plastic fine particles in internally unstable soils and their mechanical consequences. Soil samples with two gradations, on the borderline of stable and unstable and one fully unstable, were prepared using moist-tamping and wet pluviation techniques and were subjected to a two-hour downward seepage. The erosion progress and pre- and post-erosion drained mechanical behaviour of samples were investigated. Tests result showed a difference in the erodibility of fine particles for the sample on the borderline of internal stability prepared by different techniques, but similar mechanical behaviours for both gradations.