Analytical models for consolidation of unsaturated composite foundation improved by impermeable columns and PVDs

Abstract

In this study, two equal-strain consolidation models centred on an impermeable column and a prefabricated vertical drain (PVD), respectively, are developed for the study of unsaturated composite foundations reinforced by impermeable columns and PVDs. The analytical solutions, accounting for the smear effect, well resistance, and time-dependent loading, are obtained through the application of the constant of variation method, Fourier series expansion, and decoupling technique. The validity of the proposed solutions for both distribution modes is then verified by comparing it with the analytical solution for the consolidation of PVD-improved composite foundations. Finally, the analyses are conducted to examine the effects of loading rate, smear parameter, well resistance factor, and distribution pattern on consolidation behaviors during multi-stage loading. Notably, it is observed that the consolidation completion time is unaffected by the loading rate, instead relying on the magnitude of the loading values. The presence of multiple smear zones, resulting from the installation of impermeable columns and PVDs, amplifies the smear effect on consolidation. Additionally, increasing the number of PVDs is found to have a notable effect on accelerating the consolidation rate; however, it is crucial to consider the accompanying increase in well resistance.