Breach mechanism and numerical modeling of barrier dam due to overtopping failure

Abstract

As a production of natural process, the barrier dam has its own features, and is easily to fail due to overtopping. Based on the breach mechanism revealed by small-scale model tests and the draining case of Tangjiashan Barrier Lake, a numerical breach model for barrier dam due to overtopping failure is put forward. In terms of the geometrical characteristics, physical and mechanical properties of barrier dam, a unified approach is developed to model the evolution of breaches in the dam crest and downstream slope, as well as the morphological change of the barrier dam in streamwise. Furthermore, different failure modes, such as one- and two-sided erosion, incomplete and base erosion are taken into account. The draining of Tangjiashan Barrier Lake is adopted to testify the present model, and the comparison of measured and calculated results indicates the rationality of the present model with the relative errors are less than 10% for peak discharge, final breach widths, and time to peak; in addition, the calculated breach discharge hydrograph and the changing process of water level are in accord with the measured data. The sensitivity analysis shows that the residual dam height after breaching and soil erodibility affect the breach flow prediction of the barrier dam significantly, whereas the one- or two-sided breach mode is less sensitive.