e layers of sand, gravel, stones, clay, loam or similar bulk or other material to a height of at least 10 cm,...http://www.google.com/patents/US4421439?utm_source=gb-gplus-sharePatent US4421439 - Supporting fabric for bearing bulk material and a method of building a road, dike or dam embankmentAdvanced Patent SearchPublication numberUS4421439 APublication typeGrantApplication numberUS 06/180,785Pu