6. The time for a clay layer to achieve 90% consolidation is 15 years. The time required to achieve 90% consolidation; if the layer were twice as thick, 3 times forr permeable and 4 times more compressible would be :
8. The process of manufacturing steel by heating short lengths of wrought iron bars mixed with charcoal in fire clay crucibles and collecting the molten iron into moulds, is known as