Calcareous sand is widely spread in South China Sea. As the sea-filling materials in construction of artificial islands

its permeability has significant influence on the consolidation and settlement of soil mass. The drag coefficient

as the effect of fluid drag force acting on the particle surface

plays an important role on the permeability of calcareous sand

which is not extensively studied by researchers so far. Based on the experimental results of calcareous sand particle settling in various fluids

a new drag coefficient model has been proposed. The new model is now incorporated into the CFD（computational fluid dynamics）-DEM（discrete element method） program and is used to simulate the settling process of calcareous sand particles in fluids. By compared with the experimental results

the CFD-DEM program with new drag coefficient model is validated and it also shows its accuracy in predicting the settling behavior of calcareous sand particles of irregular shape over the existing drag coefficient model without considering the effect of particle shape. On the other hand

the utility of spheres used in CFD-DEM model instead of non-spheres can greatly reduce the computational cost and meanwhile represent the effect of particle shape on the drag force. This CFD-DEM approach is promising and will be applied to the analysis of consolidation

settlement and souring of sea-filling projects with calcareous soils.