Effects of plastic reinforcement on unsaturated soil and its centrifuge modeling for an embankment

Abstract

Recent case histories show the importance of incorporating unsaturated soil mechanics in geotechnical engineering practice for the design and construction of resilient and cost-effective systems. Unsaturated soils are a three-phase material- solid, liquid and gas, resulting in three interfaces. In addition to study the behaviour of flexible PVC plastics in unsaturated soils a method is proposed for characterizing an unsaturated soil deformation for a site based on reliability concepts using a sample of road embankment design. The present study includes understanding the behaviour of plastic reinforcement in unsaturated soils and its modelling for embankment. In this research paper three different types of soil have been tested. Cohesive (CH), cohesive friction (MI) and cohesion less (sand) are sampled and tested in the laboratory. Main factors considered to evaluate the effectiveness of PVC plastic material in all types of soils are shear strength parameters [cohesion(C) and angle of internal friction (Φ)] and settlement (deformation) by variations of moisture content and reinforcement materials. To find out settlement on embankment model centrifuge test is used: whereas triaxial compression test is used for shear strength parameters. The comparison of the results shows that PVC plastic granules are more effective in CH soil by increasing internal angle of friction and decreasing cohesion both by increasing amount of plastic granules and water content up to optimum moisture content, whereas the effect of plastic granules not significant on cohesion less soils compared with cohesive and cohesive friction soils. From centrifuge modelling it is concluded that the settlement for cohesion less soil declines for increase in water content as well as plastic granules, whereas for cohesive and cohesive friction soils sudden increase in settlement occurs.