双层堤基管涌破坏过程中上覆层渗透破坏发生发展的 试验与分析

利用室内试验模拟了刚性盖板下双层堤基渗透破坏的过程,研究了堤基发生管涌破坏后对上覆黏土层的影响。通过肉眼观察,照相机辅助拍摄及试验过程中测压管水位,流量和出砂量等的变化,分析了管涌过程中刚性盖板下黏土层破坏的发生及发展过程。堤基发生管涌破坏后,砂层上部细颗粒逐渐流失,形成强渗流通道并逐步向上游发展。渗流通道与上层黏土之间形成脱空,黏土层发生轻微沉降变形,在水流作用下产生不均匀变形导致黏土层中裂纹的产生并在水力劈裂作用下裂纹逐渐变成裂缝并越来越大,水流通过裂缝在塌陷黏土与刚性盖板之间急速流动,产生冲刷,破坏范围随管涌的发生向上游发展。黏土层的破坏促进了管涌的发生,而管涌通道不断向上游发展也加速了黏土层的破坏,两种过程相互作用,相互影响。

Laboratory tests on development of seepage failure of overlying layer during piping of two-stratum dike foundation

The piping erosion process in two-stratum dike foundation is simulated by means of laboratory tests to study the influence on the overlying clay layer after piping of the dike foundation. Through the macroscopic observation, camera auxiliary shooting and change of piezometric level, flow rate and sand production during the tests, the occurrence of damage and developing process of clay layer under the rigid plate are analyzed. After piping, the fine sand particles on the top are gradually eroded, and a concentrated leakage passage gradually developing upstream is formed. Due to the gap between the leakage passage and the clay layer, slight settlement and flows lead to inhomogeneous deformation in the clay layer, so cracks are produced and become larger and larger under the action of hydraulic fracturing. So water rapidly flows between the collapsed clay and the cover through the crack. Under this effect, the clay layer is scoured and the range of damage develops upstream with the piping. The destruction of the clay layer promotes the occurrence of piping, and the piping passage continuously developing upstream also accelerates the destruction of the clay layer. Two kinds of processes are interactive.