Forecast climate change impact on porewater pressure regimes for the design and assessment of clay earthworks

Understanding and mitigating the impact of climate change on the built environment is becoming increasingly important worldwide. Earthworks (embankments and cuttings) supporting road and rail transportation networks often have direct contact with the atmosphere and are therefore influenced by extreme weather events and seasonal weather patterns. Atmospheric wetting and drying alters porewater pressures (PWPs) within earthworks, potentially contributing to the deformation and failure of earthwork slopes. Consequently, it is essential to understand the influence of climate change on PWPs within earthwork slopes, to inform strategies for their design, assessment and maintenance. Extensive 1D seepage analyses were carried out for typical railway embankments in the London area. The analyses showed that forecast hotter, drier summers will increase the water storage capacity of earthworks. This will lead to increased net infiltration in the winter months owing to both a forecast increase in rainfall and a longer time being required to saturate the soil pores and bring the water table back to the slope surface. Hence, despite the forecast increase in winter rainfall, this will not lead to higher design PWP regimes. The analyses were conducted for the London area, but this approach and conceptual framework can be readily adapted for other locations.