Radial consolidation analysis of layered soil under various load and drainage boundary conditions: spectral-based solutions

Geotechnical engineers often face challenges in managing the consolidation and settlement of soft soil grounds. The use of prefabricated vertical drains (PVDs) to improve soft soil foundations has garnered significant attention in recent decades. Key factors such as loading patterns, soil property distributions, and drainage boundary conditions play crucial roles in the consolidation analysis and settlement prediction in PVD-assisted foundations. Although theoretical approaches have been proposed to address real-life issues such as smear effects and well resistance, there remains a gap in comprehensive analytical solutions that account for various loading and drainage boundary conditions applicable for layered soil. This study introduces a novel approach that employs the spectral method to assess the impact of drainage boundary conditions on the consolidation of layered soil under variable loading. The proposed method integrates temporal changes in drainage boundary conditions while modelling the excess pore water pressure (EPWP) profile across different soil layers using matrix operations. Validation against laboratory and field data, as well as comparisons with existing methods, demonstrate the method’s accuracy. The effects that different rates of drain degradation can have on the consolidation of multi-layer soil are also discussed. Additionally, a parametric study is conducted to demonstrate the effectiveness of the proposed solution in evaluating the influence of drainage boundary conditions on the consolidation of multilayered soil.