Abstract: Groundwater withdrawal can cause reduction of hydraulic level in pumped aquifers and result in land subsidence. One of distinguishing features of land subsidence is the long-term accompanying deformation of soil layer, resulting from rheological characteristics of soil. In this study, an approach for land subsidence evaluation is presented based on Biot’s consolidation theory. By using semi-analytical numerical principle and viscoelastic rheological theory, the numerical scheme for coupled deformation of soil layer is derived. In the scheme, the compressible pore constituent and viscoelastic characteristics of soil skeleton can be taken into account. The proposed method does not involve numerical integrations and is naturally appropriate for decoupled parallel computing. A FORTRAN computer program is developed for the land subsidence analysis based on the above numerical scheme. After rheological models are adopted, the validities of the present method and computer program are verified by comparing the present results with the existing solutions. It can be shown that the proposed numerical results can accurately reflect the lag effect of deformation due to viscosity of soil layers. Moreover, more numerical example experiments have been conducted to investigate the influences of soil layer permeability, compressibility of pore fluid and viscosity of skeleton on long-term deformation.

Key words: groundwater level variation, land subsidence, semi-analytical numerical method, viscoelastic characteristics, rheological model