Ain Shams Engineering Journal (Nov 2023)
Installation effect of rigid inclusions in soft clay improvement
Abstract
Rigid Inclusions have been increasingly used as a successful technique for improving soft clay deposits. This technique was first introduced by Menard in the 1990s and is known commercially as Controlled Modulus Columns (CMC’s) [1]. Unlike ordinary piles that transfer the entire external loads to the stiffer-bearing soil layers, rigid inclusions are mainly used to reduce the total and differential settlements by reducing the external loads transferred to the soft soil layers. One of the challenging tasks associated with this type of improvement is to reasonably estimate the ground deformations under different loading conditions [2]. Previous research focused mainly on getting reliable estimates of the ground movements and the straining actions acting on the rigid inclusions; however, the importance of the installation effect on the predicted deformations and straining actions was not clearly considered. The current paper aims to develop a realistic approach that takes into consideration the installation effect of rigid inclusions by utilizing the cavity expansion theory to estimate the improvement in the surrounding soil properties and accordingly enhance the accuracy of estimating the deformations and the straining actions. A case study of a zone loading test performed in New Mansoura City, Egypt, is analyzed utilizing the three-dimensional finite element method, taking into consideration the installation effect of the rigid inclusion by applying radial deformations to the soil layers and estimating the enhanced soil parameters particularly the deformation modulus and the over consolidation ratio. Results of the study showed that considering the improved soil parameters results in a better prediction of the settlement values of footings resting on the improved soil compared to the measured values. The average error in the settlement values is reduced from about 74 % to about 24 % after considering the enhancement in the soil parameters due to the installation effect.
