Abstract
Geosynthetic drain (GD) are intensively and successfully used as drainage materials, such as drains to accelerate the rate of consolidation of saturated clayey soils; as a liquid collection layer in landfill; as a capillary barrier; etc. Permeability (drainage capacity) of a GD is mainly influenced by the confining pressure and the material confining it. For all the products, the drainage capacity reduces with the increase of confining pressure; and the value of confined in soil is less than that confined in rigid plates or a rubber sleeve. It is suggested that a value used for design should be determined by a test closely simulating the field confining conditions. If only manufactured value is available, reduction factors considering soil clogging etc. should be applied. Some up-to-date theories for design GD as vertical drain (PVD) and horizontal drain and in leachate collection system of a landfill have been presented.
