Abstract

ABSTRACT
Neutral Plane in Single Pile and Pile Group in Clay under Indirect Loading

Mehrdad Ghavi,
Concordia University, 2025
Clayey soils pose significant challenges for geotechnical engineering due to their compressibility and tendency to undergo considerable settlement under loading or long-term consolidation. These soils may exhibit moderate strength initially but can soften over time, especially when subjected to changes in moisture content or sustained stress, potentially leading to excessive settlements and foundation performance issues. Pile foundations are commonly used to support structures in clayey soils; however, they are susceptible to the development of negative skin friction (NSF), particularly when interacting with soft or consolidating clay layers. This condition induces additional axial loads on the piles and may compromise the structural integrity of the foundation system.
This thesis investigates the behavior of pile foundations embedded in clay through detailed finite element analysis using Abaqus. The study focuses on the effects of pile group configuration—including pile spacing, pile diameter, pile length—the influence of soil strength and deformation properties, and loading conditions on the development of negative skin friction, total load capacity, and overall foundation performance. The analysis considers both single piles and groups of four piles arranged in different configurations. Several parametric studies were conducted to assess the sensitivity of these variables under various soil and loading condition.
A numerical model was developed and calibrated based on previous experimental findings and literature data to simulate the complex interaction between the pile and the surrounding soil. Special attention was given to modeling soil behavior before and after varying key parameters. Comparative analyses of different pile group arrangements were performed to evaluate group interaction effects and their influence on drag load distribution, load capacity, and settlement behavior.
The numerical results align well with findings from the literature and contribute to a deeper understanding of pile performance in clayey soils. Practical recommendations are proposed for optimizing group pile design in such conditions, aiming to enhance the safety and efficiency of foundation engineering in problematic ground environments.