Coarse aggregate particle breakage, rockfill deformation and shear strength are affected by subcritical crack propagation, controlled by the total suction [1, 2]. In particular, the stability of marine civil engineering structures such as coastal embankments and works in river estuaries may be compromised by the action of liquid water at different salinities and the surrounding relative humidity. Nevertheless, even if vapour and liquid water at different activities are equilibrated to the same chemical potential, rockfill’s aggregate breakage, deformation and shear strength response display differentiated behavioural features despite having the same total suction. This phenomenon was analysed experimentally on quarzitic slate [3], with more significant deformations observed by liquid soaking than vapour wetting at equivalent total suction changes, both in particle breakage and compressibility tests of aggregates. Moreover, rockfill particle breakage was modelled numerically by the discrete element method DEM [4], using a procedure extended to account for relative humidity changes governing stress corrosion in oedometer and triaxial tests. This work will present the coupled hydro-chemo-mechanical behaviour of coarse granular aggregates by DEM simulations, considering the different effects of total suction on particle breakage due to changes in water vapour and liquid activity. Oedometer-type compression of arrangements of particle clumps of controlled grain sizes will be modelled including the effects of wetting by vapour and liquid into the clump breakage rule through the so-called osmotic efficiency parameter dependent on water activity [3]. The collapse due to vapour wetting will be investigated by increasing the relative humidity conditions. In addition, a sample initially soaked in water with low activity will be studied in terms of collapse after diluting the salt concentration (increasing water activity). Results will show a greater effect on the deformation of total suction conditions imposed by liquid control (water activity) than vapour control (relative humidity).