Experimental and numerical modelling of time-dependent behaviour in deep cement mixing column improved montmorillonitic clay

The time-dependent behaviour of soft and clayey soils treated with Deep Cement Mixing (DCM) columns is important for analyzing the long-term performance of civil engineering infrastructures. Previous studies on DCMinstalled composite soil (CS) have primarily focused on examining the soil strength and stiffness characteristics. The limited focus on the time-dependent settlement and stress-strain distribution of CS underscores the need for a more comprehensive understanding of this complex phenomenon. In this study, a lab-scale physical ground model is designed and developed to investigate the time-dependent settlement profile of the composite Montmorillonitic Clay soil (MMC). The settlement behaviour of the ground model is assessed using Creep Hypothesis B and the results are further validated with the Power Law Model. Additionally, a FEM-based numerical simulation is performed to examine the time-dependent settlement and the stress distribution between the column and surrounding clay soil at different depths. The results from the physical model test show that the time-dependent parameter of the ground model (i.e., DCM column installed in MMC) is proportionate to the loading rate until the failure of the DCM column is reached. However, the time-dependent parameter was found to be decreased by 59.04 % in the post-failure phase of the DCM column. This reduction indicates that the DCM column was the primary load-bearing component before its failure. The numerical study shows that the pore water pressure dissipation in the clay soil and DCM column interface was similar at various depths. The top and bottom sections of the DCM column possess higher stress levels, which demonstrates its susceptibility for failure in the DCM column.