The artificial cemented granular particles were prepared to simulate the rockfills, and conventional triaxial drainage tests were conducted to explore the mechanical properties of granular materials under different confining pressures. Furthermore, the results were simulated based on the discrete element method. Test results from the laboratory tests indicated the nonlinearity of this materials’ strength envelope. The particle flow method could be used to simulate the stress–strain and volumetric deformation properties of artificially prepared granular materials. By the simulation, the number of failure bonds and the variation of the displacement field during the test process were recorded, visually displaying the microscopic displacement and fragmentation of the internal particles.