Embankment dams constitute most of Sweden’s dam infrastructure, serving hydropower production and tailings storage. Most of these structures were built more than 50 years ago, with a central core consisting of glacial tills, which is a natural material widespread availability and low hydraulic conductivity. Today, several dams have experienced problems related to internal erosion such as sinkholes or leakage, making internal erosion an essential safety issue. Suffusion is a mechanism of internal erosion that occurs in embankment dams where fines are washed out under seepage forces. The initiation of internal erosion depends on factors such as particle size distribution of the soil, hydraulic gradient and stress conditions. Broadly graded glacial tills are heterogenous material more susceptible to internal erosion by suffusion than other soils. Understanding the initiation and progression is essential for ensuring the long-term safety and performance of embankment dams. However, the initiation of this mechanism remains partially understood. Transparent soils modelling has emerged as a valuable experimental tool for geotechnical research processes that cannot be directly observed in natural soils. By matching the refractive indices of solid particles and pore fluids, transparent soils can mimic hydro-mechanical behaviors of sands and clays, enabling non-intrusive observation of deformations, seepage, and particle migration. This capability provides a unique opportunity to observe the onset of fines detachment and migration, which are critical in the initiation of suffusion, and to reproduce soil–water interactions similar to those in natural soils such as glacial tills. The thesis investigates the applicability of transparent soils for studying the initiation of suffusion. The scope of this work comprises (i) a synthesis of current knowledge on internal erosion and transparent soil technologies, (ii) the development and characterization of transparent soil mixtures with consolidation and hydraulic conductivity properties similar to various glacial till gradations, and (iii) the design of a laboratory setup for suffusion testing using these materials. The scope is limited to validating transparent soils as surrogates for glacial tills. Suffusion tests on transparent soils will be conducted in future work to fulfill the aim of this project to study the initiation of suffusion on glacial till.
Shane Aulestia (Thu,) studied this question.