Expansive clay materials are characterised by their low hydraulic conductivity, high plasticity, and volume increase upon contact with water. These properties are highly relevant in geotechnical engineering, as they pose challenges for structures on expansive ground while also offering advantages in sealing applications.

The objective of the project is to analyse the swelling behaviour and coupled hydro-mechanical processes through experimental investigations on reconstituted clay samples. This includes radial stress measurements under oedometer conditions, determination of the critical state for dry and saturated material, and cyclic wetting and drying tests. Based on these experimental investigations, a numerical model developed by the applicants will be reviewed and extended. The modelling approach will be capable of predicting the evolution of swelling deformation and swelling pressure, as well as swelling-induced changes in hydraulic conductivity, as a function of mechanical boundary conditions.

To account for large deformations, the model will be implemented into an existing Particle Finite Element Method (PFEM) . The developed methods will be tested and validated using benchmark problems and realistic geotechnical applications.

The predictive capabilities of the developed numerical model are demonstrated by the animation and figures below. The animation visualises the progression of the saturation front in a reconstituted Opalinus clay sample and the resulting vertical deformation due to swelling.

The time-dependent development of swelling deformation due to water intake shows excellent agreement between simulation and experiment (see Figure 1b). Similarly, the simulations of loading, unloading, and reloading after the swelling phase (Figure 1c) align closely with the corresponding experimental data (Figure 1d).