堤基管涌动态发展的数值模拟

Numerical Simulation of the Dynamic Process of Levee Foundation Piping

针对表层为相对不透水的黏性土薄层,下层为砂层的二元堤基管涌问题,提出了一个模拟堤基内部以管道形式溯源发展的流土型管涌的有限元数值模型.考虑了管涌通道中含沙浓度对水流阻力的影响,按照达西公式的形式给出了管涌区域流动的等效渗透系数的计算公式,将管涌通道和非管涌区统一用常规渗流分析方法求解;引入通道边壁土壤侵蚀速率与水流剪切力的关系,建立了管道输沙平衡方程.求解渗流方程和输沙平衡方程即可获得管涌通道随时间发展的动态过程.管涌砂槽模型试验的模拟表明,该模型能够定量地模拟管涌随时间发展的动态过程.

Levee foundation piping is a complex and dynamic process. For the levee foundation with a thin layer of relatively impermeable clay over the permeable sand bed, a finite element model is presented to simu- late the source tracing development of internal soil piping. In eiew of the influence of sand concentration on the flow resistance, the coefficient of the equivalent permeability of the pipe flow is given according to the form of Darcy formula. Thus the simulation of both piping zone and the normal soil zone is unified to the conventional seepage analysis method. The relationship of soil erosion rate of the pipe wall and the shear stress of the flow is introduced into the balance equation of sediment transportation to simulate the dynamic development of the piping channel. The dynamic development of the piping channel with time is obtained by the solution of the seepage equation and the sediment transport equation. The simulation of a sand tank test on piping shows that, the model can quantitatively simulate the dynamic development of piping with time.