Effects of extreme temperature cycles on deterioration of unsaturated embankment: centrifuge and THM modelling

Although previous studies have examined embankment behaviour under wetting/drying cycles, coupled effects of temperature cycles on embankments remain poorly understood. In this study, centrifuge tests were carried out using a novel environmental chamber to investigate behaviour of unsaturated clay embankments under 10 air temperature cycles. Back-analysis was carried out using a recently developed THM constitutive model, implemented in the commercially available finite element software. Both measured and computed results consistently reveal that temperature cycles induce seasonal variations in pore water pressures. After cycles, both total and differential settlements exceed allowable service limits, despite only 17% of design service life having elapsed. This deterioration can be primarily attributed to thermal softening. Temperature cycles lead to a maximum increase in deviatoric stress of 11% at the base of embankment, driving stress states towards critical state. Plastic deviatoric strain initially increases with depth due to higher dilatancy angle, while subsequently decreases as amplitude of soil temperature change diminishes. It reaches maximum value of 4% at depth of 1-2 m, indicating potential shallow slip surface after extreme temperature cycles. The numerical package equipped with the state-dependent constitutive model satisfactorily simulates these coupled THM responses under extreme temperature cycles. These findings underscore the need to incorporate extreme thermal effects into embankment design to mitigate degradation and shallow instability in changing climate. This would be particularly important for critical infrastructure such as high-speed rail and road embankmen