SEEPAGE AND STABILITY ANALYSIS OF GEOSYNTHETIC REINFORED SOIL WALL UNDER RAINFALL

Abstract

Rainfall-induced seepage and slope instability pose serious challenges to the durability and safety of highway retaining structures, particularly along rainfall-sensitive corridors such as NH-148B (Bhiwani to Hansi). This study investigates the hydraulic behavior and stability of a 10 m high geosynthetic-reinforced soil wall (GRSW) under moderate (15 mm/hr), heavy (30 mm/hr), and very heavy (45 mm/hr) rainfall through 1:30 scale experimental modeling and numerical simulations using SEEP/W and SLOPE/W over a 24-hour period. Pore water pressure (PWP) and volumetric water content (VWC) were monitored at multiple depths, revealing that unreinforced walls exhibited significantly higher water retention and pressure buildup. Geogrid reinforcement reduced PWP and VWC moderately, while geocomposite reinforcement achieved up to 20% lower PWP and 15–25% reduction in VWC compared to unreinforced conditions. Numerical results corroborated the experimental findings, showing that geocomposites maintained lower saturation and more stable suction profiles across rainfall intensities. Stability analysis showed that unreinforced walls failed to meet the IS 6403:1981 minimum factor of safety (FOS) of 1.3, achieving only 1.06 under moderate rainfall. Geogrid reinforcement improved FOS by nearly 30% but fell below safe limits under severe conditions. Geocomposite reinforcement maintained FOS above 1.3 up to heavy rainfall, and after design optimization, offered an overall improvement of approximately 26% in FOS under very heavy rainfall.These findings highlight the superior performance of geocomposites over geogrids and unreinforced systems, due to their combined drainage and reinforcement capabilities, making them a highly effective solution for enhancing the safety and resilience of reinforced soil walls in rainfall-prone environments.