变水头下管涌细颗粒迁移试验

为研究洪峰过境堤基发生管涌时内部细颗粒运动及迁出规律,采用变水头模拟洪水,对间断级配无黏性土进行室内管涌试验。以常水头下管涌规律作为对照组,使用彩砂追踪管涌过程中细颗粒的迁移,依据试验结果对不同细颗粒含量和不同孔隙比试样的渗透系数、细颗粒流失量等进行了分析。结果表明:变水头作用下,细颗粒在下降段存在逆流运动；细颗粒流失主要集中在下游,相同试验条件下,变水头流失的细颗粒比常水头多,迁移通道贯通范围大；细颗粒含量越大,孔隙比越小,在水头循环后最大破坏水力梯度差越大,细颗粒流失越严重。

Experimental study on the migration of fine particles in piping under variable water head

In order to study the movement and migration of fine particles in piping of embankment foundation due to the flood transit, the sinusoidal water head was used to simulate the flood condition in the laboratory piping test of gap-graded non-cohesive soil. The piping rule under constant water head was used as the control group and the migration of fine particles during piping was tracked by the colored sand. The variation law of permeability coefficient, hydraulic gradient and the step-change of fine particle loss in samples with different content of fine particle and different pore ratio were analyzed according to the test results. The results show that under the variable water head, there is countercurrent motion in the descending section. The loss of fine particles is mainly concentrated downstream. Compared with the constant water head, variable head loses more fine particles and the migration channel runs through a larger area under the same test conditions. In addition, the larger the content of fine particles is, the smaller the pore ratio is, the larger the maximum hydraulic gradient difference is, and the more the loss of fine particles is.