Shear Behavior of Marginal Soil & Non-woven Geotextile System Under UU & CU Triaxial Conditions

Backfill material is one of the major constituents of Geosynthetic reinforced soil (GRS) structures. Current design guidelines conventionally recommend the use of free draining granular material as a backfill material. Owing to the fact that difficulty in finding these materials has increased the use of locally available marginal soil for the construction site as an alternative backfill. Use of marginal fill can reduce the transportation cost and environmental impact due to soil excavation and thereby reduce the overall construction cost of GRS structures. Major concern in using marginal soils as backfill is the build up of positive pore water pressure during construction, which reduces the internal shearing resistance of the soil. It also reduces the interface shear strength between the reinforcement and fill materials. The current study focuses on the shear behavior of marginal soil (SC type) and non-woven geotextile system under UU and CU triaxial testing conditions. Specimens were prepared at their maximum dry density (MDD) and optimum moisture content (OMC) with the change in number of geotextile layers. The test results revealed that the shear strength of reinforced soil increased with the number of geotextile layers in both UU and CU triaxial testing conditions. The pore pressure evolution showed the increased contractive response of marginal soil-geosynthetics system with the addition of geotextile layers. Failure pattern of the geotextile reinforced specimens exhibited bulging/barrel failure patterns between adjacent geotextile layers unlike shear band formations in unreinforced soil specimens.