Numerical Simulation Of The Whole Process Of Overtopping Breach Of Landslide Dam And Its Application

Earthquakes and heavy rainfall lead to landslides,which block the river channels and form landslides dam,often accompanied by severe weather and complex topography.The formation of landslide dams is prone to failure,which can seriously endanger the economy and livelihood of people in the downstream watershed and bring great damage to the environment.Therefore,the study of dam failure mechanism and process is particularly important to provide technical support for disaster relief and disaster emergency planning.The most common type of dam breaching is the diffuse roof breach,which involves not only the evolution of water flow on the slope,but also the rapid change of riverbed topography and the coupled water-soil interaction mechanism,which make the numerical simulation of the dam breach very difficult.In this paper,we construct a mathematical model of dam crest breach,perform coupled solution,and validate it,and address the key issues involved such as discontinuous solution,dry and wet boundaries,etc.The main work is as follows:(1)Through the previous more perfect numerical discretization and computational theory of shallow water equations,this paper establishes a one-dimensional numerical model of dam breach water flow evolution based on the finite difference method with TVD-Mac Comark format.In the processing of dry and wet boundaries,this study proposes a method to construct a false cell to reset the topographic variables,which is simpler and more convenient to handle dry and wet boundaries.Meanwhile,the source term processing and dry and wet boundary setting in the numerical discretization process adopt the differential format that is compatible with the prediction step-correction step in the TVD-Mac Comark format.(2)The accuracy,precision,and resolution of the numerical model calculation results are verified by five common classical cases.In the verification of the ideal dam break with a dry bed downstream for both left-and right-going waves,if the numerical scheme is solved in the same format,the numerical flux will be too large and thus the data will be distorted.A solution is proposed for this problem,which is well solved by improving the differential format of the left and right traveling waves during the propagation process.Different differential formats are used for the evolution of the left and right traveling waves,and the differential formats are changed simultaneously for source term processing,dry and wet boundaries,etc.The feasibility of this solution is verified by the water flow evolution process of simultaneous instantaneous dam breakage on both sides when the downstream is a dry bed.(3)Analyzing the motion characteristics of individual particles at the inclined dam slope,based on the limiting equilibrium state of the particles on the surface of the inclined dam slope,we propose an erosion equation that can correctly express the critical starting shear stress of the particles under the action of water scour,and then construct the erosion equation.The erosion equation coupled with the one-dimensional shallow water equation establishes the numerical calculation method of dam top failure,and the results of its water level process line and flow p02 rocess line are verified by the flume test case and the actual case of Tangjiashan landslide dam,and the calculated solutions are in good agreement with the measured values,which verifies the rationality of the established model.