不同结构堤基渗流的数值模拟和管涌临界条件

Numerical Study on Critical Condition of Piping in Different Types of Dike Foundations

利用有限元分析软件模拟双层堤基、三层堤基以及多层堤基内部的水力梯度分布,将堤基内部各区域的水力梯度与相应的允许水力梯度进行比较,最终确定堤基管涌发生的临界上游水头。三层堤基和多层堤基中,堤基内部存在细砂夹层,随着细砂夹层埋深的增加,管涌发生的临界上游水头逐渐增大,通道深度不断增加,管涌破坏发生的标志是细砂夹层被冲破,发生竖向流土破坏;当细砂夹层埋深达到一定深度时,细砂上部砂砾石层的渗水量增加,增加到足以将砂砾石表面的颗粒带出,管涌破坏过程与双层堤基类似,通道主要形成在黏土下部的砂砾石表面,临界水头有所减小。将该数值模拟结果与前人管涌试验结果进行比较,两者吻合度较好。

A finite element software was used to simulate the distribution of hydraulic gradient in twostratum,threestratum and multistratum foundations.The hydraulic gradient in different areas was compared to the critical hydraulic gradient of soil erosion in the corresponding area and then the critical hydraulic head of piping in the dike foundation was determined.In threestratum and multistratum foundations,the critical hydraulic head gradually increased with the burial depth of the fine sand layer and the depth of the piping passage was gradually increased.Piping happened when the sand layer broke through with the vertical soil flow.When the burial depth of the fine sand layer came to a certain value,the piping passage formed on the surface of the sandy gravel layer below the clay layer,which was similar with that in twostratum foundation.The critical hydraulic head decreased.Comparisons between the simulation results and the experimental value were conducted and the results showed that the goodness of fit was high.