Rainfall-induced instability of mountainous photovoltaic slopes under spatially non-uniform infiltration

Abstract

Rainfall-induced slope failures are among the most frequent and destructive geohazards in mountainous regions. In photovoltaic (PV) installations, panel shading and runoff concentration cause highly non-uniform rainfall infiltration, which alters pore-pressure distribution and threatens slope stability. This study develops a coupled hydro-mechanical modeling framework to investigate slope instability under spatially heterogeneous rainfall. By integrating the Richards equation, the Van Genuchten model, and the strength reduction method within a customized FLAC3D platform, the transient evolution of pore-water pressure, matric suction, and shear strength was simulated for both uniform and non-uniform rainfall conditions. The results show that PV panel shading results in pronounced hydrological inhomogeneity, creating asynchronous suction dissipation and inhomogeneous pore pressure build-up across the slope. Non-uniform infiltration accelerates localized saturation beneath exposed infiltration zones while delaying wetting under shaded areas, resulting in lateral hydraulic gradients and early pore-pressure concentration near the slope toe. The coupling between non-uniform infiltration and interlayer hydraulic contrast is the dominant process of slope failure induced by the PV system. The simulation study illustrates the results caused by such neglect of rainfall heterogeneity can lead to overly conservative estimation of slope stability and inadequate predictions of the localized risk. For mountain photovoltaic construction, the proposed framework can serve as a reliable risk-assessment tool and early-warning design tool in nature equipped with spatially variable rainfall.