Thesis
An experimental investigation into the mechanics of clay erosion
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2025
- Thesis identifier
- T17403
- Person Identifier (Local)
- 201779183
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- This thesis presents an experimental investigation of the erosion behaviour of clay, both in saturated and unsaturated states and a numerical simulation study to promote the adoption of performance-based design in flood embankments retrofitting. The erosion detachment mechanism of saturated reconstituted clay have been investigated with a miniaturized jet erosion device (μ-jet) and a imaging system. Direct observation of the detaching unit, identified as ‘flake’, during erosion has been performed and characterized based on sample preparation. A layered fabric within the samples has been identified as root cause of flake detachment and further investigated based on clay particle physio-chemical interaction. A micro-mechanical interpretation of the observed detaching unit and layered fabric have been put forward. The unsaturated soil mechanics framework have been used to re interpret a well known, standard de facto, test to measure soil erosion: the Jet Erosion Test. Different erosion responses at varying compaction water contents and dry densities were detected using a laser scanner. This enabled the measurement of both scour depth and scoured volume. The experimental study also investigated the effect of submergence time. The experimental results have shown that the submerged water jet generates a scour with a relatively complex geometry, made of a step extending over the entire cross-sectional area of the sample and a scour hole localised in the centre of the sample. The depths of both the erosion step and the scour hole evolve with the submersion time in a different fashion depending on the compaction water content. At the same time, the compaction water content generates different rates and mode of penetration of the waterfront that propagates from the surface of the sample once the sample is submerged in water before the Jet Erosion Test starts. The step developing at the top of the sample was modelled successfully by considering the failure of a horizontal infinite layer subjected to the tangential hydrodynamic stresses generated by the impinging jet. The central scour hole was assumed to be generated by a bearing capacity mode of failure triggered by the normal hydrodynamic stresses and modelled accordingly. The numerical simulation work examines the case of flood embankments in the tidal area of the Elbe River in Germany. These embankments require to be retrofitted by raising their crest from 5m to 7m because of the new projection of extreme river levels due to climate change. The conventional ‘prescriptive’ design consisting of raising the embankment by maintaining the 1:3 inclination of the landside slope is compared with the ‘performance-based’ design where the inclination of the slope on the landside could be potentially increased up to 1:1, which is shown to be sustainable if partial saturation and transient water flow are considered. Raising the flood embankment with 1:1 landside slope (rather than 1:3) could lead to expropriation cost savings of the order of €3.9M/km. For the case of a newly built embankment of 7 m height, the saving would become €4.5M/km. An approximate estimation of embodied carbon suggests that the carbon saving would be of the order of 3,100-4,200tCO2e/km.
- Advisor / supervisor
- Lunn, Rebecca
- Tarantino, A. (Alessandro)
- Resource Type
- DOI
- Funder
Relations
Items
| Thumbnail | Title | Date Uploaded | Visibility | Actions |
|---|---|---|---|---|
|
|
PDF of thesis T17403 | 2025-06-18 | Public | Download |