Two Dimensional Headcut Erosion Mathmatical Model For Breaching Of Homogeneous Embankment Due To Overflowing

Modeling and predicting of breach growth in embankments is of significantimportance for disaster mitigation and prevention, public security guarantee,promotion and ensuring of social and economic sustainable development, etc.Unfortunately, breaching of embankments is a complicated process relying on manyfactors. Especially it is not very clear how headcut erosion forms, occurs, anddevelops, which is the major course of embankment erosion due to overflowing. Stateof the art, there is not any headcut erosion mathematical model widely recognized,which restricts the development and refinement of embankment breach model.In this paper, headcut erosion for breaching of homogeneous embankment due tooverflowing is studied as the research object. Based on observation of headcut erosionof prototype embankment breaching and experiments in the laboratory and in the field,it describes the headcut erosion for breaching of homogeneous embankment due tooverflowing in detail. According to the characteristics of the headcut erosion, fourstages can generally be distinguished during the whole process of headcut erosion forhomogeneous embankment breaching due to overflowing, which are shear erosionalong headcut top surface, jet scour of foundation and headcut undermining, slopemass failure and erosion along headcut slope.Based on the headcut erosion process description mentioned above, itmathematically describes the water along headcut topsurface, nappe discharged fromheadcut edge and impingment jet in tail water zone respectively. A two-dimensionalheadcut erosion mathematical model for breaching of homogeneous embankmentsdue to overflowing has been developed, which covers the shear erosion along headcuttop surface unit, jet scour of foundation and headcut undermining unit and slope massfailure unit. The model can simulate headcut erosion process and average headcuterosion speed of two different kinds headcut foundation, which are non-erosive anderosive condition respectively. With the data of seven laboratory tests, the model predictions are in goodagreement with the experimental data. Based on the model calibration results, arelationship has been established between the soil erodibility coefficient (kd) in theerosion rate formula and the embankment soil properties. With this expression, thevalidation of the model with non-erosive foundation condition and erosive foundationcondition uses the data of other four laboratory tests, yielding reasonable agreementbetween the model predictions and the measurements.It selects four groups of model input parameters: tail water depth (hp), dammaterial erosion rate coefficients (Kd)(or foundation material erosion rate coefficients(Kd)), dam material bond strength (c) and angle of internal friction (), which areused to analyse model sensitivity with non-erosive foundation condition and erosivefoundation condition.