Arbitrary Lagrangian-Eulerian method to analyse the disturbed zone around controlled modulus columns

Ground improvement has become an important research area in geotechnical engineering due to the scarcity of naturally suitable ground conditions for construction. Application of column inclusions is one of the most popular ground improvement methods used in practice to reduce the loads transferred to the existing ground with low bearing capacity. One such technology is Controlled Modulus Columns (CMC), and they have gained popularity for their efficiency and simplicity in installation. CMC are installed using a displacement auger that laterally displaces surrounding soil. In sandy soils, CMC creates a compacted region, while in soft soils, it leads to partial consolidation and a region with reduced permeability around CMC. This study focuses on sandy soils to investigate the disturbed zone, which exhibits increased stiffness and strength relative to undisturbed ground, enhancing its ability to transfer loads. Despite its practical significance, behaviour of disturbed zone during and after CMC installation remains poorly understood in literature. This paper presents a detailed numerical investigation into installation effects of CMC in sandy soils, focusing on the formation and characteristics of the disturbed zone. Due to the large soil deformations and highly nonlinear soil behaviour involved in the installation process, conventional small-strain finite element methods are inadequate. To address these challenges, the Arbitrary Lagrangian-Eulerian (ALE) technique available in ABAQUS/Explicit is employed, enabling realistic simulation of large soil deformations. The constitutive behaviour of sand is modelled using the SANISAND model. Simulation results provide insights into the evolution of load-displacement behaviour, radial stress distribution, radial displacement and void ratio changes around the column during installation and highlight the development of significant densification and increased confinement within the disturbed zone as penetration depth increases. These findings contribute to a better understanding of ground modification mechanisms and provide a foundation for more accurate performance prediction and design optimisation of CMC.