Modeling lateral enlargement in dam breaches using slope stability analysis based on circular slip mode

Abstract Evaluation of breach flood of landslide or artificial dams is usually performed by combining the hydraulic modeling of the breach flow and geotechnical analysis of the breach channel stability. This paper is a continuation of the previous work, which mainly focused on the hydraulic aspects of a dam breach flood. Efforts have been made to improve the related slope stability analysis approach that traditionally adopts a simple wedge failure mode. The improvements includes a vertical cut at the slope toe due to soil erosion, an approach to determine the critical slip surface, the effective and total stress methods dealing with different dam materials, and a procedure to model the stepped failures of the breach bank due to continuous toe cutting. Using VBA programming, an Excel spreadsheet entitled DBS-IWHR has been developed to perform the stability analysis. This spreadsheet has been incorporated into another spreadsheet entitled DB-IWHR for the calculation of the flood hydrograph. The developed model has been tested by back analysis of the Yigong landslide dam breached at the Tibetan Plateau in China in 2000 with a flood peak of 94,013 m 3 /s. The calculated results of the final breach base level and the peak discharge are in good agreement with the field data. Further, the results are shown to be insensitive to the variations in the geotechnical parameters used in the model.