SizePerm: Hydraulic Conductivity Software - Background
Determination of hydraulic conductivity of porous media from grain size composition is an old idea. The Hazen Formula was derived in 1892 and is still the most widely recognized method of its type. In general, studies have shown that the hydraulic conductivity of porous medium is a function of both the properties of the medium and the properties of the fluid moving through the medium. This is the common thread associating all of the formulas available in this program.
The Hazen method, as well as each method included in this program, was empirically developed through experimentation. The coefficients, methods of calculating porosity and methods of calculating effective grain diameter vary based upon the individual author's experience. As indicated on screen after calculation, each method was reported in literature to be most valid for specific material sizes or size ranges. Certain coefficients and variables have been given fixed values in order to keep the program simple and easy to use. The individual formulas as well as the values used for each variable and coefficient are documented in the output report, and should be examined to determine specific applicability. The report output is both professional in it's appearance and useful in scope. The methods included provide:
- coverage of a wide range of grain sizes,
- the option of variable porosity,
- and variable compaction in the case of Uma and Hazen.
Where appropriately applied, the subject methods can provide an economic estimate of hydraulic conductivity for various applications including geotechnical studies, water resource evaluation, and environmental characterization and remediation. In our experience, these methods are accepted by the regulatory authorities and gratefully appreciated by clients.