Abstract: In practical engineering, the foundation is usually untreated, natural and heterogeneous. The phenomenon that threshold hydraulic gradient exists in clayey soil under low hydraulic gradient is gradually recognized. However, the consolidation model of heterogeneous foundations considering threshold hydraulic gradient is rarely reported. In this paper, based on seepage model considering threshold hydraulic gradient, the consolidation problem of heterogeneous foundation was studied, the change law of compressive modulus and permeability coefficient with depth under variable loads were obtained. One-dimensional consolidation model of single-layer heterogeneous foundation was established with an assumption that the compression modulus increases with depth, and the permeability coefficient decreases with depth. The influence of threshold hydraulic gradient i0, heterogeneous foundation parameter ?, x, ? and p on the consolidation characteristics of heterogeneous foundation were analyzed. The results show that, the rate of pore pressure dissipation becomes slower in heterogeneous foundation after considering threshold hydraulic gradient and settlement as well as consolidation rate of the foundation decreases accordingly. The consolidation rate is directly proportional to the value of ? and x while the final settlement of the foundation comes inversely proportional to them. The consolidation rate grows with the increase of ? and the decrease of p. However, the permeability coefficient may only change the settlement rate of foundation, which will not affect the final settlement of the heterogeneous foundations.

Key words: consolidation theory, threshold hydraulic gradient, natural heterogeneous foundation, variable load, finite difference