A suction - based breaching model for flood defence embankments subjected to overflow

Historical and recent flood events demonstrated that, very often disastrous floods occurred due to the breaching of dams, dikes and levees resulting from the overflow induced by extreme weather conditions. The breaching process of flood defence embankment is generally gradual and comprises a series of time-dependent mechanisms that may lead to the final catastrophic failure, when a gap or a proper channel develops across the embankment allowing the inundation of the protected areas. The assessment of the performance of these geo-structures during extreme weather events is, therefore, essential for flood risk management and mitigation. In the last decades, the understanding of breaching processes improved consistently thanks to an extraordinary research effort. Laboratory and in-situ tests provided an in-depth description of the fundamental physical mechanisms leading to breach initiation and growth. In many instances, the final aim of these experimental investigation was the development of breaching models able to predict modes and times of embankment failures during overflow. Despite the latest achievements, there is a general agreement that the prediction power of the numerical models currently available is still unsatisfactory such that the application in engineering practice is so far very limited. In this work, a suction – based breaching model for flood defence embankment subjected to overflow was developed, starting from the observation that at the onset of overflow the soil constituting the embankment is usually in a partially saturated state. Based on this fundamental statement a new conceptual framework to interpret the different macro-erosion failure mechanisms is presented. For the first time, the focus is moved from soil erodibility and hydrodynamic forces on the coupled soil mechanics and hydraulic phenomena that can have a significant impact on breach formation during overflow. The conceptual model is implemented adopting traditional finite element methods available to study typical soil mechanics problems. Ultimately, a qualitative validation conducted against field experiments shows that the suction-based breaching model is a promising predictive tool capable of mimicking the large-scale erosion processes like mini-slopes failures evolving with time.Historical and recent flood events demonstrated that, very often disastrous floods occurred due to the breaching of dams, dikes and levees resulting from the overflow induced by extreme weather conditions. The breaching process of flood defence embankment is generally gradual and comprises a series of time-dependent mechanisms that may lead to the final catastrophic failure, when a gap or a proper channel develops across the embankment allowing the inundation of the protected areas. The assessment of the performance of these geo-structures during extreme weather events is, therefore, essential for flood risk management and mitigation. In the last decades, the understanding of breaching processes improved consistently thanks to an extraordinary research effort. Laboratory and in-situ tests provided an in-depth description of the fundamental physical mechanisms leading to breach initiation and growth. In many instances, the final aim of these experimental investigation was the development of breaching models able to predict modes and times of embankment failures during overflow. Despite the latest achievements, there is a general agreement that the prediction power of the numerical models currently available is still unsatisfactory such that the application in engineering practice is so far very limited. In this work, a suction – based breaching model for flood defence embankment subjected to overflow was developed, starting from the observation that at the onset of overflow the soil constituting the embankment is usually in a partially saturated state. Based on this fundamental statement a new conceptual framework to interpret the different macro-erosion failure mechanisms is presented. For the first time, the focus is moved from soil erodibility and hydrodynamic forces on the coupled soil mechanics and hydraulic phenomena that can have a significant impact on breach formation during overflow. The conceptual model is implemented adopting traditional finite element methods available to study typical soil mechanics problems. Ultimately, a qualitative validation conducted against field experiments shows that the suction-based breaching model is a promising predictive tool capable of mimicking the large-scale erosion processes like mini-slopes failures evolving with time