Abstract
Filter materials are required to be cohesionless. At present, from this point of view, we have the criterion that the percentage of the soil passing the #200 sieve should be less than 5%. However we can use any soil for filters, if we can confirm their high permeability and non-cohesion. We have performed Sand Castle tests proposed by P. Vaughan in order to confirm non-cohesion of filter materials. In addition, we have discussed the method of relaxing restrictions on the percentage finer than the #200 sieve of filter materials for embankment dams.
