LARGE SCALE PHYSICAL MODEL TO INVESTIGATE THE MECHANICS OF EMBANKMENT EROSION DURING OVERTOPPING FLOW

Abstract

This paper presents the results of large scale physical model embankment failure experiments. The model simulates the failure by overtopping of three embankments that are verying in dimensions and soil type. The soil is either homogeneous pure sand or mixture of sand, slit, and clay. A new measuring technique consists of the labeled rod bridge; grids lined and captured instatanaeous picutres are utilized to monitor the failure. The flow pattern and progressive failure of embankment overtopping were investigated. The results showed four types of phenomenon during embankment failure erosion; erosion with sliding; erosion with mass failure and head cut migration. The results revealed that the recorded time to reach the full breach failure in case of mixture materials (sand, slit and clay) is seven times that with pure sand. Also, reducing embankment height to 50% (0,9m) led to increase the time to peak discharge 8,4 times that of large one (1,8m). Adding 15% clay to pure sand changes soil characteritics to (c and fi) soil which makes soil to have critical vertical cut height. Set of dimensionless regression equations are developed by using experimental data. In conclusion, types of embankment failure are defined. Adding a percentage of clay (15%) to the pure sand led to the maximum remain vertical cut height of about 50% of the calculated critical vertical cut height (Z0). Bearing in mind the limited numer of large scale testes for embankment breach in literatures, the set of data could be used for calibration of mathematical breach models and provides a reference for the flood risk management of emabnkments