Experimental Study Of The Influence On Initial Flow Of The Moraine Dam Caused By Waves

With global warming,the rapid melting of glaciers has led to frequent geological disasters in the cryosphere,mainly including ice(snow)avalanche,glacial debris flow,and glacial lake outburst.As one of the typical geological disasters in Tibet,glacial lake outburst is characterized by low frequency and strong destructiveness,It has caused serious damage to the economic and social development and the loss of people's lives and property in the Qinghai-Tibet Plateau.Ice avalanche / landslide is the main inducing factor of ice lake outburst disaster.During the process of the surge wave impacting the final moraine dike,the obvious initial breach is formed due to the strong erosion and undercutting of the first wave.The initial breach has an important impact on the calculation of the outburst model.As an important parameter of Sichuan Tibet railway,hydropower development and other major engineering construction and disaster prevention,it is very important to reasonably simulate the collapse process and accurately predict the characteristic parameters.In order to study the influence of the first wave on the initial breach of the terminal moraine dike under the condition of ice lake surge,by considering the influence of the scale of the ice lake surge,the depth of the ice lake,the shape parameters of the terminal moraine dike and other factors on the initial breach,the relevant indoor simulation experiments were designed and completed to explore the relationship between the dynamic characteristics of the first wave on the initial breach and the initial breach discharge,The empirical formula of initial breach discharge is established.The achievements and understandings are as follows:(1)Under the condition of sufficient surge scale,there is a good corresponding relationship between the surge scale and the stress on the surface of the dam body.The erosion of the surface of the dam body is mainly due to the destruction of its original limit equilibrium state.Under the action of shear force,the overflow surge makes a lot of sediment start up and transport.The coarse and fine particles are coupled with water to form turbulent two-phase flow.(2)According to the data analysis of the initial discharge and influencing factors measured by the simulation experiment,there is an obvious correlation between the relative elevation difference of water level and dam height and the discharge characteristics.The closer the elevation difference is,the greater the initial breach discharge is and the greater the discharge intensity is.The depth of the ice lake and the shape of the dam body play a major role in controlling the initial discharge,followed by the surge scale;When the aspect ratio of dam shape is less than 0.6,the initial discharge gradient is large and strongly affected by the aspect ratio;When the aspect ratio of dam shape is greater than 0.6,the influence of the aspect ratio is weak.(3)Combined with the experimental data analysis and processing,the calculation formula of initial breach is constructed.The influence of water depth on the initial discharge is lower than that of the width to height ratio of the dam body.The width to height ratio of the final moraine dike plays an important role in controlling the sediment transport on the dam crest,showing an obvious negative correlation,while the ratio of surge scale to water depth and the initial breach discharge is positively correlated.