FUNDAMENTAL CHARACTERIZATION OF SOILS FOR THE DEVELOPMENT OF AN EXPRESSION FOR PERMEABILITY FOR APPLICATION IN IN SITU TESTING (PREDICTION, COMPUTER, SIMULATION).

摘要

Soil was assumed as spatially periodic porous media and Navier-Stokes equation was solved using FEM with appropriate boundary conditions for several different arrangements. The basic variables influencing permeability were identified as specific surface areas, void ratio, particle shape, material heterogeneity and arrangement of particles in porous media.; A sensitivity analysis was carried out to obtain an expression for the permeability in terms of the above variables. A fundamental expression of permeability tensor is proposed in terms of void ratio, specific surface area, anisotropy and tortuosity due to material heterogeneity for the most common occurrence of particle arrangement. The functional relationship for specific surface area, and void ratio in the above expression turned out to be the same as that in Kozeny-Carman equation.; Comparison is made between measured vertical permeability of Silica Flour with that predicted using the expression proposed. For fine grained soils in non-polar media or coarse grained soil in any media the above expression could be used to predict permeability provided external specific surface area is known. The variation of hydraulic anisotropy with porosity follow the same exponential variation found in electrical anisotropy suggesting a one-to-one relation between hydraulic and electrical anisotropies.; Physico-chemical interaction of clay-water system could be quantified in terms of cluster concept. Permeability of six clays were predicted using a modified version of the expression proposed. Modification for the proposed expression involves the replacement of total void ratio and porosity by inter (or between the) cluster void ratio and a factor for specific surface area to include the enlarged size of the particle due to the formation of clusters.; For the In situ prediction of permeability all of the variables affecting permeability need to be predicted in situ namely: the cluster void ratio, total void ratio, specific surface area and electrical anisotropy. The methodology for in situ prediction of cluster void ratio, total void ratio and electrical anisotropy already exists. A new method of predicting the specific surface area is proposed using the in situ magnitude of dielectric dispersion. A unique correlation between specific surface area and the magnitude of the dielectric dispersion is proposed including the modification of specific surface area with clay structure.