Modelling erosion of a single rock block using a coupled CFD-DEM approach

Abstract

Rock block removal is the prevalent physical mechanism for rock erosion and could affect the stability of dam foundations and spillways. Despite this, understanding of block removal is still inadequate because of the complex interactions among block characteristics, hydraulic forces, and erosive processes acting on the block. Herein, based on a previously conducted physical experiment of erosion of a single rock block, the removal processes of two different protruding blocks are represented by a coupled computational fluid dynamics-discrete element model (CFD-DEM) approach under varied flow conditions. Additionally, the blocks could be rotated with respect to the flow direction to consider the effect of the discontinuity orientation on the block removal process. Simulation results visualize the entire block removal process. The simulations reproduce the effects of the discontinuity orientation on the critical flow velocity inducing block incipient motion and the trajectory of the block motion observed in the physical experiments. The numerical results present a similar tendency of the critical velocities at different discontinuity orientations but have slightly lower values. The trajectory of the block in the simulations fits well with the experimental measurements. The relationship between the dimensionless critical shear stress and discontinuity orientation observed from the simulations shows that the effect of block protrusion becomes more dominant on the block incipient motion with the increase of relative protrusion height. To our knowledge, this present study is the first attempt to use the coupled finite volume method (FVM)-DEM approach for modelling the interaction behavior between the block and the flowing water so that the block removal process can be reproduced and analyzed.

Keywords

• Rock erosion
• Block removal
• Incipient motion
• Coupled CFD-DEM
• Critical shear stress