Numerical Simulation Of Flood & Sediment And Safety Analysis Of Dikes In Ningxia Section Of Yellow River

The river bed of the Ningxia Plain section of the Yellow River is wide and shallow,the mainstream swing is frequent.In order to stabilize the river potential,smooth mainstream,the Yellow River Ningxia Section has established a flood control system based on embankment,river regulation project,but because of the low punching capacity of Riverbank Beach,vulnerable spot is easily washed near the shore during flood,which threatens slope stability.Floods occurred frequently and caused a great loss of lives and property.In order to study the influence of water flow scour on the stability of vulnerable slope in flood period,the flood risk information of inundated depths,flow velocity,submerge period and arrival time were obtained,and flood risk maps were drawn,which has become an important part of non-engineering measures development.This paper establishes a numerical model of sediment in a typical river section,simulates the change of river bed erosion and siltation under different conditions of water coming to sand during flood period,analyzes the law of washing and silting of Shang slope,and probes into the stability and influencing factors of Shang bank slope The research contents and achievements of this paper are as follows:(1)The modeling method combining one or two-D mathematical model is used.Firstly,a numerical model of one-dimensional water and sand in the Qingtongxia to Shizuishan River section is established,the model is determined by using the measured data rate of typical flood in 2012,and then the two-dimensional water and sediment model of Qingtongxia ? Mianjiawan and Toudaodun ? Liuqingdi is established,and the downstream boundary conditions are provided for the two-dimensional model by using the results of one-dimensional model.It lays a foundation for the study of sediment transport and the variation of river bed erosion and siltation under different conditions of water coming to sand.(2)In order to study the flood control safety of dangerous projections in different water conditions,two working conditions of medium flood condition and 20 year flood condition were considered and the water level of the Qingtongxia-Shizuishan section on flood period.The results show that,the highest water level in the Qingtongxia-Shizuishan section is lower than the elevation of the top of the two banks in the cases of medium flood and 20 year flood.11.3km,116.0km and 153.9km downstream from the Qingtongxia hydrological station,the highest water level of the river is very close to the elevation of the embankment,if a rare flood occurs,special attention should be paid to the flooding effects,and the potential risks are large.(3)In order to study the scour erosion of the foot of the vulnerable slope under different conditions of water coming to sand,five kind of calculation conditions were developed for numerical simulation.The results show that the flushing depth of the foot of the vulnerable slope is basically balanced after the flood,the balance of the riverbed is related to the average sediment content and the average flow rate of the near-shore flow during the flood,the average flow rate is the same,and the river bed depth decreases with the increase of the average sediment content.