Environmental Engineering Reference
In-Depth Information
Figure 9.18.
Influence of the type and amount of fines on permeability of concrete sand, sand-gravel
mixture and uniform fine sand (ICOLD, 1994, from US Corps of Engineers, 1986).
9.2.4
Recommended method for design of critical filters, with flow normal to the filter
The recommended method for design of critical filters, with flow normal to the filter (flow
types N1 and N2), is based on Sherard and Dunnigan (1985, 1989). They however did
not give explicit instructions on how to apply their criteria. This has been better detailed
in USBR (1987) and USDA-SCS (1994).
The following is taken largely from the US Soil Conservations Service, USDA-SCS
(1994). It has been modified to include the changes to the Base Soil Group boundaries and
