Integrating FEM with reliability-based serviceability limit state design for a test embankment on low-carbon column-stabilised soil

Dry deep mixing (DDM) is one of the primary stabilisation methods used to reduce compressibility and increase bearing capacity of soft clays under road embankments. However, geotechnical designers encounter considerable uncertainty in designing DDM columns, arising from the properties of both soil and binder, as well as the stabilization techniques employed. These uncertainties are exacerbated when using novel binders, whose behaviour in real field conditions is still under investigation. In such cases, probabilistic simulation provides a systematic approach to quantifying and managing these uncertainties. This paper presents a reliability-based design framework that combines finite element (FE) analysis using the volume averaging technique and Monte Carlo simulation. The framework accounts for the uncertainty in the calculation of residual settlements of both soil and stabilised soil parameters in the case of a testing embankment built on low-carbon end-bearing and floating stabilised soil columns. The volume averaging technique approach was validated using field measurements and was found to reasonably capture the behavior of length-varying columns. Probabilistic results show that longer columns reduce significantly not only the residual settlement but also the range of plausible outcomes and the absolute variability. However, by linking failure probabilities with binder carbon emissions, an optimal length can be obtained, enabling sustainable design and reliability adjustments based on environmental and performance trades-offs. Lastly, a global sensitivity analysis on the risk of exceedance was performed to identify the influential parameters to target in soil investigations and requiring additional testing to reduce the probability of exceedance most effectively.