Numerical Investigation into the Plane Breach Process of Cohesionless Dikes Induced by Overtopping

Abstract

Dikes made up of erodible geotechnical materials are easily broken by overtopping flow, which poses a serious threat to human lives and properties in protected areas. In this study, the plane breach of cohesionless dikes induced by overtopping was simulated via the discrete-element method coupled with computational fluid dynamics. A method of dynamically setting the permeabilities of fluid computation cells was proposed to implement the variation of the free surface of overtopping flow. The numerical model was validated using published experimental results, and the sidewall effect was also analyzed. The influence of three important factors on the dike breach process was investigated, namely, the inflow discharge per unit width, convergence area length, and particle size. The results suggest that the inflow discharge per unit width has little influence on the breach process within a range, outside which it has a promoting effect. The normalized peak breach discharge increases linearly with the increase in convergence area length. When the relative convergence area length increases to 4, the descent speeds of the convergence water level and the dike height reach a balance for a long time during the peak stage of the breach hydrograph. For the dikes consisting of uniform cohesionless particles, the breach process is linearly related to the particle size without regard to the seepage inside the dike. The findings of this study provide new insights into the mechanism of dike breach.