Abstract
The Highway embankments in the United Kingdom are experiencing deterioration over their life cycle. A lack of understanding the long-term behaviour and the different factors that can affect the stability like vegetation, can lead to uncontrolled deformation and reduce the service performance. It is well known that the complex root-soil interaction is one of the key factors thatsignificantly influence the stability of these embankments. Additionally, rainfall events can increase the possibility of shallow landslides. However, there is a lack of information about the mechanical and hydrological impact of vegetation on highway embankments in the UK under different rainfall events and vegetation types. This research provides a decision support tool to the engineers and designers regarding the behaviour of the landslide-prone vegetated highway
embankment, and it will help to understand which slope is expected to need detailed investigations and early maintenance.
To provide a better understanding of the mechanical behaviour of roots, a 3D-printed root analogue model that represents real root architecture was designed using 3D CAD software. Additionally, a Large Direct Shear Apparatus was designed, and a series of large direct shear tests were performed to investigate the mechanical impact of roots on the strength behaviour of different soil types and densities. This includes the impact of root area ratio and root morphology.
The slopes that are used in this research represent typical landslide-prone highway embankments in the southeast of England in the UK
The Combined Hydrology And Stability Model (CHASM) was used to provide a better understanding of the mechanical, and hydrological slope dynamics and vegetation effects on the stability of highway embankments in the UK. Using CHASM enabled performing 6,912 simulations in a short period of time. Those simulations were a result of a number of combinations of soil properties, slope geometries, rainfall events and vegetation types. This helps to overcome the
uncertainties regarding available data on highway embankments in the UK. The big number of CHASM outputs (6,912 output results) enabled the quantification of the main factors that can affect the stability of vegetated highway embankments. It also enabled the recognition of the factors that can cause detrimental impacts on the vegetated slopes.
Finally, the stability of vegetated slopes was analysed using Finite Element Model (PLAXIS). This enabled an understanding of the lessons learned from using FEM and LEM (CHASM) in analysing the stability of vegetated slopes. It also verified the mechanical impact of the root analogue models compared to the additional cohesion model from the literature. Furthermore, provide a suitable vegetation plan for three-real life case studies by using the PLAXIS model and the previous understanding of the behaviour of vegetated embankments.
| Date of Award | 20 Oct 2025 |
|---|---|
| Original language | English |
| Awarding Institution |
|
| Supervisor | Erdin Ibraim (Supervisor), Elizabeth A Holcombe (Supervisor) & Andrea Diambra (Supervisor) |