The particle-fluid system can be simulated with the coupling model of the discrete element method (DEM) and the smoothed particle hydrodynamics (SPH), also named DEM-SPH coupling model. The dilated polyhedron, generated by the Minkowski sum of a sphere and a randomly shaped polyhedron, is adopted in the DEM. The contact detection between dilated polyhedron can be solved according to the potential function and geometric calculations between spheres, cylinders, and faces. The weakly compressible SPH is developed to establish the DEM-SPH coupling model. The interaction force between the solid particle and fluid particle is calculated by the repulsive force model, while the geometric shapes of the dilated polyhedron are directly used in the distance calculation. The dam break and the falling cube in the water are validated with previously published results. To simulate the rock dumping on the pipeline in the water, the contact detection algorithm between the sphere, the dilated polyhedron, and the pipe is developed. Numerical examples are illustrated to validate the proposed method. The rock dumping process is simulated to analyze the force on the pipe and the morphology of the dumping rocks. The results show that the proposed method is an effective approach for the rock dumping analysis. (C) 2020 Elsevier B.V. All rights reserved.