Influence of Failure Mechanisms on Probabilistic Stability in Embankments Supported by Deep Mixing Columns with Spatial Variability in Column Strength

Deep mixing (DM) columns are extensively employed to reinforce soft soil foundations. However, the strength of these columns exhibits significant spatial variability due to inhomogeneities in the mixing process and the inherent variability of the soil. This variability complicates the interaction between the columns and the soil, thereby increasing the likelihood of inaccurately predicting the failure mechanisms of the DM columns. Previous deterministic investigations have demonstrated that the failure mechanisms govern embankment stability, highlighting the critical need to accurately identify and predict these mechanisms amid uncertainty for effective risk assessment. This study investigates the impact of spatial variability in the undrained shear strength of the columns on failure mechanisms and embankment stability. A random finite difference method, incorporating random fields with varying characteristics and Monte Carlo simulations, is utilized to model the column strength as a stochastic parameter. Failure mechanisms are quantitatively identified and characterized through statistical analysis of multiple realizations. The study further examines how variations in these failure mechanisms impact embankment reliability and the failure envelope curve. Sensitivity analysis evaluates the effects of random field characteristics on failure mechanisms, revealing that transitions in failure mechanisms lead to high failure probabilities and significant variations in envelope curves.