Presented here is a numerical method able to predict the mechanical behaviour of granular materials subjected to particle removal. The purpose of this study is to improve understanding of the mechanical behaviour of soils subjected to internal erosion in hydraulic works. The approach is based on a homogenisation technique for deriving the stress–strain relationship of a granular assembly from forces and displacements at the particle level. The soil’s local behaviour is assumed to follow a Hertz–Mindlin elastic law and a Mohr–Coulomb plastic law. Sliding resistance on each plane is made to depend on the actual void ratio of the granular assembly. The solid fraction removal is modelled by progressively increasing the granular assembly void ratio, which provokes a decrease of the sliding resistance of each interparticle contact, leading to macroscopic deformations of the soil specimen. At elevated stress levels, large deformations can develop and lead to soil failure. Numerical simulations also demonstrate that a type of failure called diffuse failure can occur in eroded soil masses whenever an increase in pore pressure is generated within the soil. These numerical results appear to be coherent with observations made on embankment dams that have suffered internal erosion and, in particular, with the description of their modes of failure;