To date, few researches have been contributed to the excavation failures frequently caused by rainstorm events featuring different rainfall patterns, especially those in erodible sandy strata. To explore the characteristics and failure mechanisms of both sloped shallow and multi-propped deep excavations in sandy strata associated with intense rainfall, this study employed a computational fluid-dynamic (CFD) and discrete-element-method (DEM) coupling method (CFD-DEM), which was validated by a typical failure of a sloped excavation triggered by heavy rainfall in China. Subsequently, extensive parametric studies were carried out to investigate the effects of rainfall amounts and patterns on the excavation responses. It was disclosed that for a sloped shallow excavation retained by soil nails, rainfall infiltration caused initial instability at the slope toe and then incurred sliding failure along a linear slip surface; regarding a multi-propped deep excavation, sand flowing failure occurred and its basal strata underwent evident upward movements, accompanied by kicking out of the embedded retaining wall. With increasing of precipitation and variation coefficient of rainfall patterns, excavation deformations increased and the rainfall-induced primary displacement zone (PDZ) expanded as well. Finally, simplified solutions were proposed to estimate the distribution of PDZ.