A Geometrical Pore Model for Estimating the Microscopical Pore Geometry of Soil with Infiltration Measurements

This paper presents a simple geometrical pore model designed to relate characteristic pore radii of the porous network of soils with macroscopic infiltration parameters. The model composed of a stack of spherical hollow elements is described with two radii values: the pore access radius and the actual pore radius. The model was compared to cylindrical pore models and its mathematical consistency was assessed. Soil sorptivity S and the second parameter A of the Philip infiltration equation (1957), have been determined by numerically simulated infiltration. A diagram and an empirical relation have been set in order to relate the pore access and pore radii to the infiltration parameters S and A. The consistency of the model was validated by comparing the predicted sorptivity and hydraulic conductivity values, with the widely used unsaturated soil hydraulic functions (van Genuchten, 1980). The model showed good agreement with experimental infiltration data, and it is therefore concluded that the use of a model with two radii improves the relation between microscopic pore size and macroscopic infiltration parameters.     

A geometrical model for numerical simulation of capillary imbibition in sedimentary rocks

The cylindrical model is discussed and a new tube model is proposed to describe capillary imbibition kinetics in porous sedimentary rocks. The tube consists of a periodic succession of a single hollow spherical element of which the geometry is defined by the sphere radius and the sphere access radius. These two parameters are estimated experimentally for four rock types from their specific surface areas. Introducing those parameters in the model capillary imbibition kinetics, parameters are calculated and compared with the experimental ones. A direct relation between imbibition kinetics and specific surface area has been pointed out.     

Modelling the capillary imbibition kinetics in sedimentary rocks: Role of petrographical features

The kinetics of capillary imbibition into sedimentary rocks has been measured experimentally and calculated with a model that has been described previously by Hammecker and colleagues (1993). The validity of this model has been discussed and compared to other models. Three limestones, two clean sandstones and three clayey sandstones have been studied. The capillary processes are discussed as a function of their petrography and the pore structures. The role of the grain surface, described by the specific surface area, has been especially studied. The influence of clay coating on detrital grains on capillary processes has been quantified.Nomenclature A weight increase rate by capillary imbibition (A=W/(S ₁t)) - B capillary rise rate (B=l/t) - l height of the capillary fringe or the meniscus over the free water level - g gravitational constant - L height of the geometrical elements - P _a pressure in the air - P _c capillary pressure - P _w pressure in the water - Q flow rate - N _l free porosity - Nt total porosity - r radius of the pore (meniscus) - r ₁ pore access radius (neck) - R pore radius (widening) - R _s particle radius - S specific surface area - S ₁ macroscopical area of the sample surface throughout which imbibition occurs - t time - W weight - z height - surface tension - dynamic viscosity - contact angle - density - _r true density