Coupling of a water permeability function with a bounding surface hydromechanical model for unsaturated soils

Abstract

This paper presents a water permeability function that predicts the hydraulic conductivity of deformable and unsaturated soils as the product of two interacting terms. The former term accounts for the effect of the degree of saturation, suction, particle size distribution, particle shape and soil fabric on the water permeability at a given void ratio. The latter term describes instead the influence of the void ratio on the saturated permeability. Overall, the resulting water permeability function is dependent on five model parameters: two parameters can be estimated from permeability tests on saturated soils, another parameter is dependent on the particle size distribution of the soil while the remaining two require unsaturated testing. The proposed water permeability function has then been coupled with the bounding surface hydromechanical model proposed by Bruno and Gallipoli (2019). The coupled model was then validated against three sets of experimental data published in literature. Results show the good capability of the coupled constitutive framework to capture the variation of water permeability of soils with different granularities ranging from clay to sand. Finally, the proposed coupled model can be implemented into a Finite Element code to study coupled flow-deformation problems in geotechnical and geo-environmental engineering.