The paper presents a numerical study on the erosion of sand particles where hydrodynamic forces induced by liquid flow are considered to be dominant in a weakly bonded sand assembly under conditions relevant to sand production. The numerical approach employed is the coupled discrete element method (DEM) and computational fluid dynamics (CFD). The sand assembly modelled is composed of sand particles which are weakly bonded. Bond breakage occurs when the resolved normal and shear stresses in the bond exceed the bond strength. The disaggregated sand particles are then transported by liquid and considered as produced sand. The simulated results show that the main features of sand erosion can be captured by the CFD-DEM approach. It is also shown that the increase of axial compaction enhances sand erosion, and the increase in radial confining pressure can cause continuous sanding. The effects of different variables on erosion rate are examined, showing that particle-fluid interaction force is indeed the main driving force for sand erosion. Cavity formation is also examined by simply assigning a non-uniform bond strength distribution to the sand assembly. Cavities tend to form and grow within weaker regions. The results show that the proposed model offers a promising method, which should be further developed, to elucidate mechanisms governing the erosion of sand particles at a particle scale. (C) 2011 Elsevier B.V. All rights reserved.