Permeability Testing in Unconsolidated Materials
by: Sebastien Fortin, E.I.T., M.Sc.
Empirical Methods
As hydraulic conductivity can be readily measured in the laboratory, there have been numerous attempts to relate the measured values to various properties of a porous medium. One commonly accepted relationship has been proposed by Hazen (1991):
Another formula of the form given by Equation 4 has been proposed by Harleman and others (1963), stated as
where k is the permeability in cm2 and d10 is again the effective grain size in cm. Several other empirical methods such as Masch and Denny (1966) and Krumbein and Monk (1943) were proposed to correlate permeability with grain size but are not discussed any further in this document.
In addition to these empirical approaches, there are other, more hydraulically-based attempts to relate permeability to porous medium properties. Kozeny (1927) considered the porous medium to be a bundle of capillary tubes and demonstrated that permeability must have the form
where C is a dimensinless constant that takes on values of 0.5 for circular capillaries, 0.562 for square capillaries, and 0.597 for equilateral triangles; k is permeabilty in L2; n is porosity; and S* is the specific surface, defined as the interstitial surface area of the pores per unit bulk volume of porous material.
One of the better known hydraulically-based models is the Kozeny-Carmen equation, stated as
where K is hydraulic conductivity, rw is fluid density, m is fluid viscosity, g is the gravitational constant, and dm is a representative grain size (Bear, 1972).
Other hydraulic models exist, such as Collins (1961) that considers tortuosity and pore size distribution, but are not discussed any further in this document.
Forward to Laboratory Methods.
Return to Methods of Permeability Testing.
Consult list of References on Permeability Testing.
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