Taking the variations of hydraulic conductivity and storage coefficient into account for modelling hydrogeological processes and consolidation in saturated clays

It is well known that the consolidation of compressible silt-clay geological layers induces a decrease in porosity. Consequently, the hydraulic conductivity and the compressibility of the medium are also decreased and the hydrodynamic conditions changed. A full coupling between the groundwater flow and the subsidence processes must be taken into account with non-linear parameters. In saturated conditions, the specific storage coefficient is directly related to the volume compressibility of the medium; its evolution depends on the rheological law chosen to describe the consolidation of the medium. For the hydraulic conductivity, the choice of the variation law is more difficult and should be made in each case as a function of the experimental data and measurements. Comparisons are made between computations with constant and varying parameters. The computed pore pressures are strongly affected, automatically inducing the major differences in the calculated subsidences. Different laws of non-linearity for the hydraulic conductivity are tested on a practical case taken from the study of the land subsidence in Shanghai. This subsidence was induced by heavy groundwater withdrawal.