Towards migration of fines within a soil matrix

Abstract

Suffusion is an internal erosion mechanism observed in embankment dams, caused by washing out fine-grained particles within the dam core as a consequence of seepage with various hydraulic gradients. The initiation of internal erosion is conditional upon three primary factors: grain size distribution, stress conditions, and hydraulic gradient. Graded moraines, such as glacial tills, exhibit an increased susceptibility to suffusion when compared to other soil types used in dam construction. Many Swedish embankment dams in mining and hydropower industry were constructed with glacial till cores over 50 years ago, lacking specific guidelines related to grain size boundaries for core and filter materials. This deficiency has given rise to instances of internal erosion, therefore elevating safety concerns. Previous research aimed to enhance dam safety by exploring the susceptibility of glacial till soils to suffusion. Silva (2022) reviewed existing methods for assessing soil susceptibility, comparing testing conditions, and presents an experimental study on critical hydraulic gradients for suffusion initiation in glacial till soils. Results indicate the critical hydraulic gradient depends upon testing conditions, including axial loading, the rate of gradient increase, and time intervals. Furthermore, it underscores the efficacy of Kenney and Lau (1985, 1986) method for assessing suffusion susceptibility. These insights offer valuable contributions to the assessment and mitigation of internal erosion in embankment dams, thereby addressing a significant safety concern within the Swedish dams infrastructure. Silva (2022) has offered valuable insights into suffusion phenomena while the intricacies of erosion processes remain unclear, hindering the implementation of rehabilitation measures to ensure the longevity of embankment dams. A follow-up project utilizing the advantages of transparent soil seeks to further comprehend the migration of fines within a soil matrix. Transparent soils, emerging as a viable alternative with likely properties to sand and clays, consist of a two-phase medium by refractive index allow solids to represent the soil skeleton and a fluid solution to mimic pore fluids. Various solids, such as amorphous silica, silica gel, hydrogel, fused quartz, and laponite, have been employed in conjunction with fluid solutions, depending on the solid, as mineral oil and paraffinic solvent, calcium bromide brine, sucrose solution, or water. Transparent soils offer the potential to replicate the behavior of glacial till cores employed in embankments, particularly those designed for the storage of tailings material in the mining industry, and water retention for hydropower. The applicability of these findings may address and enhance rehabilitation measures in such structures, which are imperative to mitigate potential socio-economic and environmental ramifications in the event of failure. Given the escalating global demand for mining resources and renewable energy, proactive measures are essential to predict long-term issues looking for a more sustainable and efficient construction methodologies to extend infrastructure lifespans.