Hydro-mechanical behaviour of composite-geosynthetic-reinforced soil walls with marginal lateritic backfills through instrumented model tests

To examine the hydro-mechanical behavior of Geosynthetic Reinforced Soil Walls (GRSW) backfilled with locally available marginal lateritic soils, physical model tests were conducted during construction, surcharge loading, and rainfall infiltration. Various reinforcements were tested, including a conventional geogrid (GG) and two types of composite geosynthetic reinforcements (CGR) with equivalent stiffness but different configurations. The results showed that suction was maintained throughout surcharging, but during rainfall infiltration, the GG model lost suction after 12,240 min, while both CGRs retained it. Strain evaluations indicated that all reinforcements remained within serviceability limits during surcharging, but the GG model exceeded these limits during rainfall, while the CGRs stayed within acceptable limits with minimal strain increases. Additionally, the GG model showed a 61% increase in facing deformation during rainfall, exceeding serviceability limits, whereas the CGRs remained within permissible limits. The study emphasizes the importance of cautious use of marginal soils in backfill applications. These soils can still be suitable for GRSW when reinforced with composite geosynthetics, especially CGR made of polyester geogrids with non-woven geotextile bonded longitudinally to the polyester strips. This configuration demonstrated superior performance by reducing facing deformation through better drainage and improved soil-reinforcement interaction.