Empirical Estimates of Permeability for Earth Dam Projects

Seepage models for earth dam projects require estimates for the coefficient of permeability for each zone in the cross-section.  Models also require an estimate of the anisotropy of the permeability in the zone (anisotropy is the ratio of the horizontal to vertical permeability values of the permeability).  Computations of drain designs require accurate estimates of the permeability of filter and drainage materials.  Empirical estimates provide a basis for determining the reasonability of tests and assumptions used for models. 

This webinar covers a number of useful empirical tools historically used for estimating the permeability and anisotropy values for a variety of soil types.  It concentrates on estimates for higher permeability coarse-grained sands and gravels because they provide the more problematic seepage.  Techniques covered include charts such as the Casagrande and Fadum and Freeze and Cherry tables.  Empirical estimates relating grain size distribution and permeability are covered including the Hazen equation, the Slichter method, Chapuis’s equation, and the Kozeny Carman relationships.  Guidance is provided on typical values for the anisotropic ratio.

Examples and problems are used to provide practice to participants in using each of the methods.