冰盖前缘冰坝形成及演进过程的离散元-水动力学耦合分析

Discrete element analysis of ice jam formation and evolution on leading edge of ice cover

基于冰盖影响下冰坝形成和演进的动力特性,该文针对冰坝与冰盖相互作用及冰盖破碎问题,在离散元河冰动力学模型的基础上,发展了具有冻结破碎功能的黏结失效模型,对碎冰在冰盖前缘堆积形成冰坝以及冰盖前缘破碎、冰坝推进下移的过程进行模拟。模拟结果显示:该模型能够较全面地描述冰盖前缘冰坝形成和冰盖破碎冰坝推移的过程;冰盖会导致堆冰发生在冰盖前端或冰盖底部,冰坝体的平衡状态受到来冰量、河道边壁阻力、冰盖强度和水力等因素的影响;冰盖在水位变化条件下先沿河岸纵向断裂,进而冰坝与冰盖前端作用并向下游推移,冰坝推移过程中冰坝与冰盖的作用力是累积-释放的循环过程;由冰盖前端破碎产生的碎冰会造成更严重的堆冰和河道壅水。模拟结果对现场观测难以捕捉到的动力过程及过程中水力、冰力等信息做出了描述,可为冰坝形成和演进的机理研究及冰区凌汛的防治提供参考。

To model the interaction between ice jam and ice cover and solve the problem of ice cover breaking,a bond and failure model is established on the basis of DEM river ice model.The process of ice blocks pile-up,ice jam formation,ice jam and ice cover interaction,and breakage of ice cover are simulated.The result shows that ice jam can form at the leading front or on the bottom of the ice cover and will be influenced by ice discharge,bank resistance,ice cover strength and hydraulic condition.The compression of the ice rubble can lead to the destruction of the edge of the ice cover.The force between the ice jam and the ice cover is a cumulate-release cycle while ice jam pushing downstream.The breaking blocks from the ice cover will be incorporated into the jam rubble and cause more serious backwater.The simulation shows the model is capable of reproducing the detailed dynamic process that is difficult to capture by on-site observations,and the results can provide references for the investigation of the mechanism of ice jam formation and evolution,as well as the prevention of ice floods.