Experimental And Numerical Study On Erosion Process Of Homogeneous Embankment Breaching Due To Overtopping

As one of the most common engineering measures for flood protection, embankments are often constructed along the rivers to constrain flood. Of all the kinds of embankments, those made of earth are the most widely applied because of the low price and convenience of using local materials. However, it is impossible to make sure embankments are absolutely safe. Non-reasnable design, construction methods and materials, complex foundation condition and extremely large flood flow may all lead to the failure of embankments. Overflow is the most common style of embankment failure. Study on the breaching process of embankments is of great significance for determing embankment design standard, assessing flood inundation loss, making emergency planning and rapid breach-plugging scheme.It is difficult to get field data of embankment breaching because embankment breaching is usually a sudden and dangerous occurrence. So physical and numerical models are more practical and this paper studies breaching process of homogeous earth embankment breaching by means of the above two kinds of models.The main content are as follows.Nine groups of flume experiments for non-cohesive embankment breaching due to overtopping are conducted to study the breaching and water level process under different discharge, different intial dike height and different construction materials.Then a series of flume experiments for cohesive embankment breaching due to overtopping are conducted. The main factors considered include discharge, soil moisture content and porosity. The headcut erosion type, widening process and the final style of the burst are stuied. Accordingly, the water level change, the flow velocity process in front of the breach and their correspondence with breach development are analyzed.A two-demensional flow and sediment transport numerical model of dike overflow breaching is established. The basic equation can reflect the effect of bed deformation on current. Flow numerical flux is acquired by Rimmen approximate solution of Roe and MUSCL-TVD type is used to reconstruct the conservation variable at both sides of the interface. Sediment numerical flux is got by first-order upwind scheme. Time discretization of the flow equations is the second-order Prediction-correction sheme while that of sediment equations is first-order forward Euler format. Burst widening is calculated by underwater erosion and collapse above the watre method.The model is used to calulate breaching discharge process under different upstream discharge, different dike construction materials and initial dike height. The difference of water level and breach discharge changes due to different breach development is analyzed. Breaching discharge of both cohesive and non-cohesive embankment overflow breaching are calculated and analyzed.Breach development process and affecting factors of the overflow failure of cohesive and non-cohesive embankment are compared. The breaching discharge processes are also different according to different breach development.