Hydro-mechanical behaviour of a geosynthetic reinforced soil wall with fine-grained backfill under rainfall conditions

Abstract

The use of fine-grained soils as backfill in geosynthetic-reinforced soil walls has increased worldwide, despite concerns regarding climate-induced intense rainfalls. This study investigates the hydraulic–mechanical behaviour of a large-scale segmental reinforced soil wall constructed with a fine- grained backfill and subjected to controlled rainfall and drying cycles. The experimental program was conducted under laboratory conditions and included instrumentation to monitor soil suction, volumetric water content, face displacements, and geogrid strains. Results show that the structure remained stable even under prolonged and intense rainfall. This performance is mainly attributed to the low hydraulic conductivity of the well-compacted backfill, which favoured surface runoff and preserved suction-induced apparent cohesion. Although suction decreased during rainfall events, it was not fully eliminated, and partial recovery was observed during drying stages. Facing displacements exhibited a rotational pattern, with outward movements near the top and inward movements near the base, governed by the interaction between soil pressures and reinforcement layers. Rainfall-induced displacements were concentrated in the upper portion of the wall and did not affect the final facing inclination. Tensile loads in the geogrids increased with surcharge application and were further amplified by wetting, resulting in a non-linear load distribution with depth. Continuous rainfall of 10 mm/h for more than seven days proved insufficient to fully dissipate suction in the reinforced soil mass.