关键词: 双层地基, 起始水力坡降, 大变形固结, 非线性固结, 有限差分

Abstract: Layered distribution of natural soft soils and the threshold gradient of the flow in soils have been gradually recognized. However, with consideration of the threshold hydraulic gradient and the nonlinear compressibility and permeability, the theory of large-strain consolidation of double-layered soil has rarely been reported in the literature so far. In this study, a model for large-strain nonlinear consolidation of double-layered soil is developed in Lagrangian coordinate by employing the excess pore water pressure as a variable. Meanwhile the corresponding finite difference solution for this model are provided. The numerical solution for the proposed model is verified by comparing with the numerical solution of large-strain nonlinear consolidation of a single-layered soil with threshold gradient. Finally, the influences of dimensionless parameters R1, R2 on consolidation behaviors are analyzed. The differences of the dissipation of excess pore water pressure, and the differences of the consolidation settlement under large- and small-strain conditions are investigated. The results show that the influences of R1 on consolidation behavior of double-layered soil are more evident than that of R2; the moving speed of seepage flow front of double-layer soiled under large-strain assumption is faster than that under small-strain assumption; the dissipation rate of excess pore pressure under large-strain assumption is faster than that under small-strain assumption, and the settlements of double-layered soil with threshold gradient under large-strain assumption is larger than that under small-strain assumption.

Key words: double-layer foundation, threshold gradient, large-strain consolidation, nonlinear consolidation, finite difference method