Vertical drains can be used in low permeability soils (clays, silts) and might substantially raise the rate of consolidation. Prefabricated vertical drains include a versatile plastic Main (flat or cylindrical in shape) wrapped in the spun-bond filter material and will be installed to depths of much more than fifty m. https://manueltlbui.blogocial.com/bd-civil-engineering-consultancy-can-be-fun-for-anyone-68960240