Abstract: For the deep investigation of the consolidation mechanism of sand well foundation in saturated clay region, this paper introduces the unified hardening model considering the time effect to describe the deformation nonlinear relationship of the soil skeleton under the assumption of Barron's free strain, meanwhile, the exponential seepage equation is introduced instead of Darcy's law, and the influences of permeability coefficient change and smearing effect are taken into account, the influence laws of soil nonlinearity, construction disturbance and external loading on the nonlinear consolidation process of sand well foundation are investigated. The results show that the viscous effect of soil causes the increase of pore pressure near the undrained boundary of the sand-drained ground in the early stage of loading. The non-Darcy characteristic of flow makes this phenomenon more obvious, and also significantly delays the consolidation rate of the sand-drained ground. In addition, the decrease of permeability coefficient in the smear zone can significantly reduce the dissipation rate of the overall pore pressure of sand-drained ground, while increasing the external load accelerates the consolidation process of the foundation.