To investigate the one-dimensional nonlinear consolidation characteristics of a double-layer foundation under multi-stage loading, a one-dimensional nonlinear consolidation equation for the double-layer foundation was established, and numerical solutions were obtained through the finite difference method. The accuracy of the proposed solution was validated by comparing it with existing analytical solutions and finite element analysis results. Based on these comparisons, the influence of nonlinear parameters, double-layer soil properties, and loading conditions on the consolidation behavior of the double-layer foundation was further examined. The results indicated that, under multi-stage linear loading conditions, an increase in the initial permeability coefficient ratio of the double-layer foundation resulted in a significant reduction in excess pore water pressure and an acceleration of consolidation. The compression index was found to predominantly affect the later stages of consolidation, with minimal impact on the early stages. The consolidation rate was observed to increase as the permeability coefficient ratio decreased. Despite notable differences in early consolidation behavior under varying loading conditions, the findings reveal that these discrepancies are alleviated in the later stages, ultimately resulting in no significant overall difference in the time required for the foundation to achieve complete consolidation.

The self-weight stress in multilayered soil varies with depth, and traditional consolidation research seldom takes into account the actual distribution of self-weight stress, resulting in inaccurate calculations of soil consolidation and settlement. This paper presents a semi-analytical solution for the one-dimensional nonlinear consolidation of multilayered soil, considering self-weight, time-dependent loading, and boundary time effect. The validity of the proposed solution is confirmed through comparison with existing analytical solutions and finite difference solution. Based on the proposed semi-analytical solution, this study investigates the influence of self-weight, interface parameter, soil properties, and nonlinear parameters on the consolidation characteristics of multilayered soil. The results indicate that factoring in the true distribution of self-weight leads to a faster dissipation rate of excess pore water pressure and larger settlement and settlement rate, compared to not considering self-weight. Both boundary drainage performance and soil nonlinearity have an impact on consolidation. If the boundary drainage capacity is inadequate, the influence of soil nonlinearity on consolidation diminishes.