Simulation of weather-driven deterioration of clay embankments

Clay embankments used for road, rail, and flood defense infrastructure experience several weather-driven deterioration processes that lead to a progressive degradation in their hydromechanical performance. This paper presents a numerical modeling approach that accounts for the development of desiccation cracking in clay embankments. Specifically, a bimodal soil-water retentivity model was adopted to capture the long-term hydraulic behavior of clay embankments prone to weather-driven desiccation cracking. A numerical model was developed for a heavily instrumented and monitored full-scale research embankment with long-term field data. The model was able to capture the variation of near-surface soil moisture and matric suction over a monitored period of nine years in response to weather cycles. The developed and validated numerical modeling approach enables forecasting of the long-term performance of clay embankments under a range of future climate scenarios.</p

Strength parameter selection framework for evaluating the design life of clay cut slopes

Design of engineered earthworks is predominately conducted through limit equilibrium analysis requiring strain independent strength criteria. Previous studies for deep-seated first-time failures within over-consolidated clay cut slopes have proposed the use of fully softened strength parameters for design. A study investigating shallow first-time failures in clay cut slopes due to seasonal stress cycles has been undertaken using a validated numerical model capable of capturing seasonal ratcheting and progressive failure. It is shown that fully softened strength criteria are inappropriate for the assessment of shallow first-time failures due to seasonal ratcheting and that slopes at angles between the material’s fully softened and residual friction angle may be at risk of failure in the future due to this behaviour. However, adopting residual strength parameters will likely result in overly conservative solutions considering the required design life of geotechnical assets. It is shown that the strain softening behaviour of clay defines the rate of strength deterioration and the operational life of engineered slopes. While general guidelines for analysis considering shallow first-time failures in clay cut slopes are made, detailed understanding of a material’s strain-softening behaviour, the magnitude and rate of strength reduction with strains, is needed to establish strength criteria for limit equilibrium analysis

Evidence for the weather-driven deterioration of ageing transportation earthworks in the UK

Seasonal, weather-driven pore pressure cycles alter and degrade the hydro-mechanical engineering properties of earthworks as they age. The accumulating effects of deterioration over many years can lead to the excessive deformation or failure of earthworks; requiring interventions to ensure their reliable performance. This paper reviews the evidence for the weather-driven deterioration of ageing transportation earthworks, with a focus on clay earthworks in the UK. These include earthworks of various ages (up to ∼200 years old), formed from a range of clay-rich strata and at various stages of deterioration. Evidence is considered for both past behaviour and projected behaviour in response to continued ageing and a changing climate. There is clear evidence that some clay earthworks are influenced by the cumulative effect of seasonal weather cycles over many decades. Simulations show that seasonal slope ratcheting will become an increasingly dominant driver of shallow failures in high-plasticity cut slopes as they age and in response to projected climate change. The evidence can inform performance curves describing the deterioration of individual earthworks in response weather-driven ageing. This can help identify earthworks with the highest likelihood of failure and inform decisions made by earthwork asset managers.</p