Reliability assessment for serviceability limit states of stiffened deep cement mixing column-supported embankments

The reliability and deterministic analyses of wood-cored stiffened deep cement mixing and deep cement mixing column-supported embankments (referred to as WSCSE and DCSE, respectively) considering serviceability limit state requirements are presented in this paper. Random field theory was used to simulate the spatial variability of soil−cement mixing (SCM) material in which the adaptive Kriging Monte Carlo simulation was adopted to estimate the failure probability of a column−supported embankment (CSE) system. A new method for stochastically generating random values of unconfined compressive strength (qu) and the ratio (Ru) between the undrained elastic modulus and qu of SCM material based on statistical correlation data is proposed. Reliability performance of CSEs concerning changes in the mean (μ), coefficient of variation (CoV), and vertical spatial correlation length (θv) of qu and Ru are presented and discussed. The obtained results indicate that WSCSE can provide a significantly higher reliability level and can tolerate more SCM material spatial variability than DCSE. Some performance of DCSE and WSCSE, which can be considered satisfactory in a deterministic framework, cannot guarantee an acceptable reliability level from a probabilistic viewpoint. This highlights the importance and necessity of employing reliability analyses for the design of CSEs. Moreover, consideration of only μ and CoV of qu seems to be sufficient for reliability analysis of WSCSE while for DCSE, uncertainties regarding the Ru (i.e. both μ and CoV) and θv of qu cannot be ignored.