Development and verification of a coefficient of permeability function fora deformable unsaturated soil

The modelling of flow through saturated/unsaturated soils has become routin e in geotechnical and gee-environmental engineering. The analysis requires that the coefficient of permeability for an unsaturated soil be defined. Th e coefficient of permeability can be estimated based on currently available procedures. However, each procedure has limitations and consequently cares should be taken in the selection of a proper procedure. The coefficient of permeability of a saturated soil is a function of void ratio. The coeffici ent of permeability of an unsaturated soil of constant volume, is a functio n of the degree of saturation. However, soil is deformable and both the deg ree of saturation and the void-ratio influence the coefficient of permeabil ity of a compressible, unsaturated soil. In this paper, the literature pert aining to the coefficient of permeability function for an unsaturated soil of constant volume and the coefficient of permeability for a deformable sat urated soil are reviewed. A new coefficient of permeability function for a deformable unsaturated porous medium is then developed. A series of triaxia l permeameter tests on unsaturated silty sand are described and the results from the experimental program are analyzed using the general form of the n ewly developed permeability function. The results show good agreement betwe en the experimental data and the proposed model for a deformable unsaturate d porous medium.