Behaviour of Gravel Compaction Piles in Soft Clay

Gravel Compaction Pile (GCP) is one of the most widely used ground improvement techniques in the field of civil engineering for enhancing soft ground characteristics. However, notable knowledge gaps remain in understanding the behaviour of GCP-improved ground. Therefore, a numerical analysis was conducted using Plaxis-2D software to study the behaviour of GCP improved ground. Two models were developed using plane strain and axi-symmetric conditions and both models were validated using the data collected from the actual projects and existing literature. A parametric analysis was then performed using both models. The effect of permeability of GCP material was studied by considering the permeability ratio between GCP and surrounding soft soil. Based on the analysis, it was identified that when the permeability ratio exceeds 100, the stability of the GCP improved ground increases. The effect of the stiffness of the surrounding soil was also examined for different permeability ratios by considering different volumetric compressibility ratios. Additionally, this paper discusses the impact of encasement on composite ground by considering different encasement stiffnesses. Finally, the critical length of the GCP was determined as 11-12 m for ground improvement in very soft soil.