Hydro-Mechanical Response and Damage Mechanisms of Geosynthetic-Reinforced Slopes under Rainfall Infiltration: An Integrated Experimental and FLAC3D Numerical Study

Slope failures due to rainfall are one of the main factors that cause damage to transportation infrastructures, embankments, and earth structures even with reinforcement in the tropical and sub-tropical areas. This paper uses combined experimental and numerical methods to study the hydro-mechanical behavior of geosynthetic reinforced slopes as well as the morphing of the damage process as a result of rainfall infiltration. The new research method is making use of instrumented rainfall flume bench-scale experiments coupled with hydro-mechanical advanced simulations done with the software FLAC3D for an in-depth evaluation of transient pore-water pressure changes, matric suction reductions, slope deformation as well as reinforcement loading under different rainfall intensities. High-tech monitoring techniques such as tensiometers, pore-water pressure transducers, TDR moisture probes, strain gauges, and laser displacement sensors were deployed to the experimental program. All of these were combined to trace the coupled hydraulic and mechanical response of a partially saturated reinforced slope under rainfall infiltration. Variably saturated flow using Richards’ equation, soil-water characteristic curves using van Genuchten relationship, effective stress concept using Bishop’s formulation, and Mohr-Coulomb constitutive model were numerically simulated to replicate infiltration-led failure phenomena. The findings illustrated that rainfall intensities remained the primary factor controlling degradation and stability loss through hydro-mechanical interaction. Heavy rainfall brought about very quick positive pore-water pressure build-up, facilitated fast loss of matric suction and favored the formation of localized saturation zones next to the interface of the reinforcement layers. These were the main causes of the significant rise in reinforcement thrust and deformation build-up. When put against low-intensity rainfall scenarios, high-intensity admission caused reinforcement thrust to increase by roughly 175% and the factor of safety was downgraded from stable to near-failure levels. Parametric studies disclosed that drainage systems markedly raise the performance of reinforced slopes by controlling pore-pressure build-up and hastening post-rainfall dissipation. The FLAC3D modeling platform validated against the experimental data demonstrated an excellent match with the experimental results and thereby served as a powerful tool for performance-based design evaluation under short-term rainfall occurrences. Besides, the research presented fruitful design guidelines and stability maps that relate rainfall intensity, duration, reinforcement arrangement, and drainage features to slope performance. These results greatly help in understanding the hydro-mechanical coupling processes in reinforced slopes and therefore constitute a useful reference for designing climate-resilient geotechnical infrastructures facing increasing rainfall extremes due to climate change.