Desiccation Cracking: A Weather-driven Deterioration Phenomenon Affecting Infrastructure Slope Resilience

Abstract

Weather-driven deterioration of infrastructure embankments is an increasingly severe threat to their stability, longevity, and safe operation. Dry-wet cycles within compacted clay fill instigate shrinking and swelling, forming micro- and macro-scale cracks that drive irrecoverable microstructural changes. This degradation reduces the clay fill’s water retention capacity, exacerbating the rate, magnitude, and consequence of these dry-wet cycles. Therefore, understanding the timescales of microstructural degradation and desiccation cracking’s role within this is crucial to ensure the long-term serviceability of the transport network. Laboratory tests, while informative, often fail to capture field scale heterogeneity. To bridge this gap, an intermediate-scale, compacted clay slope was constructed within an outdoor lysimeter. This novel approach provided high-resolution spatial and temporal monitoring, revealing that cracking severity depends on exposure to physical and environmental boundary conditions. Desiccation cracks significantly altered slope hydrology, locally deepening evaporation and infiltration fronts by up to 400 mm and extending weather-driven deterioration to 200 mm. Deep summer crack networks (2021-2022) markedly increased rainfall storage capacity, allowing full infiltration of three simulated 1-in-100-year storm events (each delivering 52 mm of rainfall in one hour, with climate change uplifts applied) and producing no runoff. The resulting soil moisture increase resulted in a sharp decrease in suction, culminating in complete suction loss by the end of the third event. In contrast, shallower crack networks in Spring 2023 generated runoff under the same storm profiles. Seasonal drying patterns were also disrupted, maintaining high moisture contents that suppressed suction generation and inhibited deep cracking observed in prior summers The lysimeter slope enabled real-time monitoring of desiccation drivers, informing targeted laboratory-scale tests. These experiments provided insight into how altering the physical and environmental boundary conditions through modifying parameters in the Penman-Monteith (1965) equation can influence moisture transfer dynamics and desiccation behaviour within Ampthill Clay fill. Overall, this research qualitatively and quantitatively underscored desiccation as a key accelerator of weather-driven deterioration. Furthermore, it emphasised that all contributing elements to desiccation must be considered to fully assess their risk to infrastructure embankment stability.