One‐dimensional consolidation for multilayered unsaturated ground under multistage depth‐dependent stress

Due to the phenomenon of stress decay in space, the total vertical stress varies with depth in the layered soil stratum. The physical properties of unsaturated soil stratum and the nonuniformity of external load in vertical direction pose significant effects upon the consolidation process, while related works have viewed modest development at present. Therefore, the main objective of this study is to explore the one-dimensional (1D) consolidation patterns of multilayered unsaturated ground considering depth-dependent stress by a semi-analytical procedure. According to the 1D consolidation theory of unsaturated soils put forward by Fredlund and Hasan, the semi-analytical solutions of excess pore pressures and settlement are derived with the combination of Laplace transform and matrix transfer method. Crump's method is then adopted to obtain the analytical solutions in the time domain, and the corresponding computing programs are compiled. Furthermore, the validity work of proposed solutions is conducted by comparing the current solutions in this paper with degenerated ones under constant load in existing literature. Concentrating on the double-layered unsaturated ground, and by considering different physical parameters of separate layer, the 1D consolidation characteristics under depth-varying stress resulting from two-stage load are investigated. The major conclusion can be drawn as that the settlement with constantly distributed stress along depth is overestimated compared with that considering the depth-varying stress.