Geological disasters such as slope failure and landslides can cause loss of life and property. Therefore, reproducing their evolution process is of great importance for risk assessment and mitigation. The recently developed SIMSAND critical state sand model combined with the smoothed particle hydrodynamics (SPH) method is adopted in this work to study slope failure under large deformations. To illustrate the efficiency and accuracy of the SIMSAND-SPH approach, a series of slope collapse studies using the discrete element method (DEM) considering various particle shapes (i.e. spherical, tetrahedral and elongated) is adopted as benchmarks. The parameters of the SIMSAND model are calibrated using DEM triaxial tests. In comparison to the DEM simulations, the runout distance and final slope height are well characterized with the SIMSAND-SPH approach with less computational cost. All comparisons show that the SIMSAND-SPH approach is highly efficient and accurate, which can be an alternative numerical tool to simulate real scale granular flow.