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Transparent Soils for Studying Internal Erosion
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.ORCID iD: 0009-0002-8074-129X
2026 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Luleå: Luleå University of Technology, 2026.
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keywords [en]
Internal erosion, Suffusion, Glacial tills, Transparent soils
National Category
Geotechnical Engineering and Engineering Geology
Research subject
Soil Mechanics
Identifiers
URN: urn:nbn:se:ltu:diva-115609ISBN: 978-91-8048-957-7 (print)ISBN: 978-91-8048-958-4 (electronic)OAI: oai:DiVA.org:ltu-115609DiVA, id: diva2:2017465
Presentation
2026-02-06, E246, Luleå University of Technology, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2025-12-01 Created: 2025-11-28 Last updated: 2026-01-16Bibliographically approved
List of papers
1. Internal erosion in tills: mechanisms and a novel approach using transparent soils - A review
Open this publication in new window or tab >>Internal erosion in tills: mechanisms and a novel approach using transparent soils - A review
(English)Manuscript (preprint) (Other academic)
National Category
Geotechnical Engineering and Engineering Geology
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-115608 (URN)
Available from: 2025-11-28 Created: 2025-11-28 Last updated: 2025-12-01Bibliographically approved
2. Study of development of internal erosion by use of transparent materials
Open this publication in new window or tab >>Study of development of internal erosion by use of transparent materials
2025 (English)In: Book of Abstracts of the 30th Meeting of the European Working Group on Internal Erosion in Embankment Dams, Levees and Dikes, and their Foundations and of the 5th Meeting of the European Working Group on Overflow and Overtopping Erosion / [ed] Laura Tonni; Stéphane Bonelli; Jean-Robert Courivaud; Michela Marchi, University of Bologna , 2025, p. 37-38Conference paper, Oral presentation with published abstract (Refereed)
Place, publisher, year, edition, pages
University of Bologna, 2025
Keywords
Internal erosion, transparent soils, suffusion, silica
National Category
Geotechnical Engineering and Engineering Geology
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-115032 (URN)
Conference
30th Meeting of the European Working Group on Internal Erosion (EWG-IE) and the 5th Meeting of the European Working Group on Overflow and Overtopping Erosion (EWG-OOE), Bologna, Italy, September 9-13, 2024
Projects
Swedish Centre for Sustainable Hydropower - SVC
Available from: 2025-10-07 Created: 2025-10-07 Last updated: 2025-11-28Bibliographically approved
3. Towards migration of fines within a soil matrix
Open this publication in new window or tab >>Towards migration of fines within a soil matrix
2024 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

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.

Place, publisher, year, edition, pages
Copernicus GmbH, 2024
National Category
Geotechnical Engineering and Engineering Geology
Research subject
Soil Mechanics
Identifiers
urn:nbn:se:ltu:diva-113084 (URN)10.5194/egusphere-egu24-20090 (DOI)
Conference
EGU General Assembly 2024, Vienna, Austria, April 14-19, 2024
Note

Full text license: CC BY

Available from: 2025-06-10 Created: 2025-06-10 Last updated: 2025-11-28Bibliographically approved

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Aulestia, Shane

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Citation style
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