Strength variability of deep cement mixed columns on the overall performance of column-supported embankments

Abstract

Deep Cement Mixed (DCM) column improved ground is known to have large strength variability across the material domain. However, the effect of strength variability on the performance of embankments supported by DCM columns is not well studied due to scarcity of numerical modelling facilities to incorporate spatial variability of material properties directly into a finite element analysis and lack of comprehensive field monitoring data. This paper investigates the effect of spatial variability on the performance of an embankment with attached DCM column walls beneath the side slopes. The analysis was carried out using numerical models developed using ABAQUS finite element program incorporating the spatial variability of DCM columns. The strength field in the material domain was randomly generated, from a lognormal distribution, using a computer program written in MATLAB. The sensitivity of embankment deformations to spatial correlation length, coefficient of variation (COV) and partial factor of safety (PFOS) was investigated by analysing a series of models. The reliability of the embankment in each analysis case was assessed using 1500 Monte Carlo realizations. Results demonstrate that the spatial correlation length of strength properties has a great influence on the reliability-based performance of the embankment. Larger spatial correlation lengths resulted higher upper bound in the lateral deformation data of the embankment. COV also affected the upper and lower bounds of the lateral deformation data. The PFOS significantly affected the skewness of the deformation distribution, however PFOS does not affect the upper and lower bounds of the distribution