中文摘要：

渗流场分布确定是管涌研究的基础与关键。双层堤基管涌时土体破坏范围仅局限于管涌口周围，且在管涌口形成后土体中的渗流场会经历一个动态的变化过程。基于此，将管涌1ml概化为半球状的涌水井，结合非稳态渗流方程和叠加原理，对定水头条件下双层堤基管涌口形成后地层中的流场分布进行了研究，得到了管涌口形成以后的渗流场分布。通过算例，研究了管涌口形成以后堤基内水头以及水力梯度随时间的变化规律；通过与稳定条件下完整井流的对比，得到了球状井与完整井条件下水头与水力梯度的分布规律。研究表明：管涌口形成时的非稳定渗流是造成细砂突涌的重要原因之一；利用稳定完整井条件下的渗流场分布进行管涌判别时，会明显夸大管涌的发生范围。

英文摘要：

Seepage field distribution is a basis of the piping study. The piping area is limited around the piping mouth in two-stratum dike foundation. The seepage field will experience a dynamic change process after the piping mouth formation. For the above-mentioned reasons, an unsteady seepage model of the piping foundations combined with an unsteady flow equation and superposition principle is proposed with the piping mouth generalized as a spherical well. And then the seepage field distribution is given by analyses. Through an example, the change rules of the water head and the hydraulic gradient with time after the formation of the piping mouth are studied. And then analyses of differences between the seepage field distributions under the spherical well and the fully penetrating well are also carried out. The analysis results show that the unsteady seepage around the piping mouth as its formation is one of the most important reasons for the water and soils rushing out when the piping mouth forms. And the piping area would be erroneously judged with the results from seepage distribution formed by the fully penetrating well.