Effect of Short- and Long-Term Seasonal Climate Change Variations on the Stability of a Vegetated Slope in London Clay

Abstract

Slopes, such as in a soil cutting, are prone to instability caused by seasonal climate variations. The seasonal climate variations result in drier/wetter summers and winters, causing fluctuations in pore-water pressure (PWP) and suction within a slope. Alternating cycles of such seasonal climate variations over time cause PWP to fluctuate between high PWP and high suction, resulting in progressive shear failure and instability of a slope. Existing studies focus on the hydraulic behavior of slopes without simultaneously considering their mechanical behavior. This study presents a methodological framework for evaluating the impact of short- and long-term seasonal climate variations on the hydrology and stability of a vegetated slope in London clay. The effects of historical and future climate variations of precipitation, humidity, air temperature, wind speed, and potential evaporation are examined using a numerical model. A validation of the numerical model shows that the PWP and suction predictions made from the present study are in good agreement with on-site measurement and numerical modeling data available in the literature. The validated numerical model is used to predict PWP and suction variations, slope displacement, and the global factor of safety of the slope. It is observed that significant fluctuations in PWP and suction occurring due to extreme weather scenarios, such as longer, drier summers and wetter, warmer winters, adversely affect slope stability. While periods of high suction during dry seasons temporarily enhance slope stability, the following periods of high PWP during wet seasons reduce it, posing a significant threat to the stability of the slope. Using 30-year future climate projections, the study predicts intensified cycles of drying and wetting and, as a result, more PWP and suction fluctuations, further challenging slope stability. The findings highlight the critical need to integrate future long-term seasonal climate variations in the design and maintenance of geotechnical structures.