| China is the country with the widest distribution and most types of glacial lakes.With the development of China's western development strategy in the 13 th Five-Year Plan,it is expected that the Sichuan-Tibet Railway will have the construction conditions at the end of the third quarter of 2019.Its pathway is characterized by glacier development,glacial lake distribution,steep mountain peaks and frequent seismicity.Because of the poor structural stability of moraine dams,it is easy to cause dam damage under the action of earthquakes.Meanwhile,seasonal rainfall will cause unstable landslides around the dam to start,and landslides fall into the lake will generate larger surges.The phenomenon of surges caused by earthquakes,single landslides and even landslides is likely to occur.In this thesis,the characteristics of landslide surge,earthquake and comprehensive surge of landslide group are analyzed.Finally,the effect of surge height on dam break is studied experimentally.The main conclusions are as follows: 1.Based on orthogonal theory,25 sets of landslide-triggered surge experiments are designed.The experimental results show that the main factors affecting the wave height are the impact velocity and the slide thickness,followed by the slide length,slide width,slide entry angle and still water depth.The statistical relationship between maximum wave height and control variables is given.Combined with the continuous equation and motion equation of the openchannel unsteady flow,it is found that the attenuation of the wave height obeys the exponential distribution.and then the attenuation formula of the surge is proposed according to the data obtained by the experiment.Finally,the proposed maximum surge formula is verified by using the observation data of landslide surge in The Zipingpu Reservoir in Wenchuan,and the results show that the calculated value is very close to the actual observation.2.A large-scale shaking table water tank model experiment was carried out,different seismic waves were used as disturbance seismic sources,the height characteristics of surges generated by different water depths under the action of different seismic accelerations were studied,and the calculation formula of surge height under different initial water depth,different sources and different seismic accelerations were summarized.The results of the experiment were compared with the results of the video analysis of the Mexicali pool.The probability of ice lake outburst caused by different earthquake-exceeding probabilities is estimated by this formula.3.The surge effect of earthquake and landslide and landslide groups was analyzed by using large-scale shaking table experiments.It is found that the wave sources excited by the two landslides with the same initial phase are in the superposition region of the wave.When the wave path difference is zero or an integral multiple of the wavelength,the combined amplitude is the largest and the wave heights are superimposed on each other.When the wave path difference is an odd multiple of a half wavelength,the combined amplitude is the smallest,and the wave heights cancel each other out;Therefore,the maximum composite wave height generated by the double landslide exhibits a periodic change with the gradual increase of the distance between the two sliders.Based on the experimental results,the calculation formula of the wave height under the combined action of earthquake and landslide is proposed,and the complex wave height triggered by the earthquake and landslide group is discussed and defined.4.The experiment of glacial lack outburst induced by the wave overtopping was carried out,and the influence of the initial wave height on the dam outburst was studied.The experimental results show that the wave overtopping is the direct trigger factor of the dam outburst,the initial wave height will affect the time required for the formation of the outburst,and the shape of the discharge hydrograph generated by different wave height is also different.The smaller the scale of the surge,the smaller the erosion rate of the dam.The scour movement of the water in the dam back side will make the dam form a gully.The scour movement of the water in the back side will make the dam form a gully,when the gully developed to a certain extent,the interaction between the water flow and the bottom bed changed from shear action(friction resistance)to impact action,which greatly increased the erosion and destruction capacity of the water flow and formed a "headcut".The water flow constantly brushes the bottom of the "headcut" and produced retrospective erosion,make the break constantly expanded,eventually result in dam break. |
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