<p>Buried pipelines may experience uplift buckling once the upward stress surpasses the overburden resistance, a risk that is not yet fully characterized in partially submerged to fully submerged soils. To address this issue, this study examines pipeline uplift in various groundwater levels using a coupled smoothed particle hydrodynamics and discrete element method (SPH–DEM) framework. In this approach, the water is represented as a weakly compressible Newtonian fluid through SPH, whereas the soil mass is explicitly resolved at the particle scale using DEM. The results showed that the soil arching ratio and stress ratio exhibit consistent evolutionary patterns, with rapid initial changes followed by stabilization. Increasing burial depth strengthens and stabilizes soil arching, whereas elevated water levels suppress arching development by delaying stress release and increasing residual stress. These hydraulic effects are most pronounced under shallow burial, while deeper embedment promotes more stable load transfer and stress redistribution. Trapdoor uplift induces a distinct passive soil arch under dry conditions, while increasing water level suppresses vertical deformation and shear localization, leading to laterally confined, water-level-controlled failure. Groundwater reduces mean normal and tangential contact forces, accelerates coordination number loss under shallow burial, and weakens friction mobilization, whereas increased overburden confinement restores contact force stability. Overall, hydraulic effects degrade passive soil arching primarily by impairing frictional force transmission rather than altering contact network geometry.</p>