Evaluation of permeability characteristics of a geosynthetic-reinforced soil through laboratory tests

The objective of this paper is to examine the permeability characteristics of geosynthetic layers under confinement with soils having relatively low permeability. For this purpose, a large permeameter was custom designed and a series of permeability tests were carried-out by varying soil type and number of geosynthetic layers. Further, effect of provision of sand cushion and the thickness of sand cushion on permeability characteristics was also examined. Normal stress was increased in intervals of 50 kPa up to 200 kPa. With an increase in normal stress, a decrease in the permeability characteristics of a geosynthetic-reinforced soil was observed. The permeability characteristics were found to improve significantly with the provision of sand cushion and an increase in its thickness. Based on the definition of equivalent coefficient of permeability of stratified soils for parallel flow, an equation for estimating coefficient of permeability of soil–geosynthetic system with and without sand cushion is proposed. Considering the application of geosynthetics in reinforced slopes and walls with low-permeable backfill soils, a suitable geosynthetic with a thin layer of sand cushion is recommended. This in turn can also help in enhancing the pore-water pressure dissipation.