Consolidation responses of rheological aquitards to tide-induced groundwater fluctuations in coastal soft deposits

Abstract

To investigate the consolidation responses of coastal rheological aquitards to tide-induced groundwater fluctuations, this study adopts a nonlinear 1-D consolidation model considering the rheological properties of the aquitard and non-Darcian flow. In this model, the depth-dependent property of the initial permeability and compressibility of the aquitard are considered using the continuous exponential functions of the vertical coordinate z. Moreover, the stress-dependent property of the permeability and compressibility during consolidation are described using the correlations of the void ratio with effective stress and permeability coefficient. The rheological nature of the aquitard is characterized with the e-log t curve for the secondary consolidation, while the flow in the aquitard is assumed to follow the exponential non-Darcian law. The numerical solutions for the model are obtained using finite volume method and Newton-Raphson iteration method. A comprehensive parametric study is conducted with regard to the mechanical and hydraulic parameters of the aquitard and its burial conditions. The analysis results reveal the generation, accumulation and oscillation mechanisms of pore pressure change and soil skeleton deformation in the aquitard. The proposed model can provide a theoretical foundation for predicting and controlling the deformation of engineering structures in coastal aquitards.