In this work a particle method (PM) based on the discrete element method (DEM), including hydromechanical coupling [1], is proposed for rubble stone masonry dam stability analysis. Many old dam masonry structures require rehabilitation and retrofitting works, and it is known that most problems are related to the cohesion loss due to water chemical and physical effects. The structural evaluation of rubble stone masonry dams is a complex task due to the heterogeneity and uncertainty in the properties of the constituent materials and the known variability of stone geometry and positioning. A micro-modeling strategy based on a detailed particle model (PM) that follows a discrete element method (DEM) that has been applied in the modelling and evaluation of traditional stone masonry unreinforced walls [2] is adopted and extended to consider hydromechanical coupling. The calculation cycle of the PM hydromechanical contact model is based on a coupling scheme between both the mechanical and hydraulic models. The hydraulic apertures are defined considering the local contact point normal displacements (mechanical model) and the water pressures calculated with the hydraulic model that are transferred to the mechanical model and are subsequently considered in the calculation of the local contact force (effective contact forces) The masonry dam stability analysis is carried out by amplifying the hydrostatic loads, by gradually increasing the reservoir water level to simulate an overtopping scenario. Parametric studies are also carried out to assess a potential loss of cohesion due to the chemical and physical deterioration caused by water flow through the dam discontinuities. The results presented highlight the relevance of considering a hydromechanical model when carrying out stability assessment. It is shown that the adopted micro-modelling approach can be readily used in the assessment of rubble masonry dams’ stability safety, including the failure scenario due to loss of cohesion within the dam body. REFERENCES [1] Farinha, M.L.B.; Monteiro Azevedo, N.; Oliveira, S. Safety Assessment of Concrete Gravity Dams: Hydromechanical Coupling and Fracture Propagation. Geosciences, 15, 149 (2025). [2] Azevedo, N.M.; Pinho, F.F.S.; Cismasiu, I.; Souza, M. Prediction of Rubble-Stone Masonry Walls Response under Axial Compression Using 2D Particle Modelling. Buildings, 12, 1283 (2022).