Experimental and Numerical Investigation on Scour Pits of Granular Flow Downstream Check Dam

In this study, experimental and numerical investigation were conducted on scour pits of granular flow downstream. Firstly, the flow flume experiment studied the influence of the material mass from the source area, the initial location of the material, the height of the check dam, and the length of the entrainment area. In the experiment a wedge was used to simulate the check dam. Then a numerical research of typical experiment processes was carried out using the discrete element method. The experiment results show that apparent entrainment only occurs under specific conditions of high initial energy, low wedge height, and small length of entrainment area. Based on the numerical verification, the numerical results obtained by the discrete element method were used for analysis, which show that the formation of the scour pit undergoes three main sub-stages, including downstream impact entrainment at the initial sub-stage, retrospective scraper entrainment toward the upstream at the middle sub-stage, and shear deformation zone formation in the entrainment area by friction and pushing at the later sub-stage. The damage caused by shear deformation in the entrainment area deserves special attention, as this area is difficult to observe directly. However, it can influence the stability of scour pits and surrounding structures. The results of this study may provide the basis for further research on the scour pits.