Investigation of temperature effects on slope serviceability and subsequent rainfall-induced instability: a comparative centrifuge study

Under a changing climate, the serviceability and stability of slopes are significantly influenced by the extreme temperature and rainfall. However, the distinct impacts of varying temperature loading patterns on the thermo-mechanical response of slopes and the resulting instability during subsequent extreme rainfall events remain underexplored. This research investigates the effects of different temperature loadings on slope serviceability and explores the role of temperature-induced desiccation cracks in compromising slope stability during subsequent extreme rainfall. Two centrifuge tests were conducted, each involving a temperature loading (i.e. thermal cycles or elevated temperature) followed by extreme rainfall with 100-year return period. During the temperature loading phase, both slopes experience settlement exceeding 1% of their height, approaching the threshold for serviceability breach. The slope subjected to elevated temperature continuously settles, whereas the slope subjected to thermal cycles exhibits downslope ratcheting movement. Due to the higher evaporation rate induced by more extreme temperature boundary, the slope subjected to elevated temperature possesses higher crack intensity factor (1.2% vs. 0.6%) and deeper crack depth (5.4 m vs. 3.8 m) compared to the slope subjected to thermal cycles. These crack characteristics are critical in influencing failure mode during extreme rainfall period, as they alter the rate at which preferential flow saturates the soil. This can further affect the rate of soil shear strength reduction and the formation of slip surface. Consequently, the slope subjected to elevated temperature experiences progressive failure with its slope angle degrading to the soil friction angle, while the slope subjected to thermal cycles undergoes substantial settlement over 10% of its original height.