北江大堤典型堤段管涌试验研究与分析

用北江大堤典型堤段的堤基粉细砂砾在玻璃水槽中模拟不同砂层厚度、埋深、层次结构及接触面粗糙度等条件下的管涌试验。论证了接触面加糙后能使临界坡降由光滑面的0．10提高到0．13～0．20。较细的上层砂和较粗的下层砂砾将有可能使临界坡降减小30％左右。最后，根据多层地基渗流理论推导出堤基渗流管涌发展的计算公式，并用三维有限元计算进行了验证。该公式可以用来估算管涌突发时的涌砂范围和继续向上游冲蚀发展的距离，以便判别危害大堤安全的程度。

Experimental study and analysis on piping of levee in Beijiang River

The soil samples excavated from the levee foundations in Beijiang River, China, were used to study the behaviors of piping in laboratory. The levees with different thickness of fine sand located at different levels of foundation possessing different interface roughness were considered. The study result shows that the critical gradient of seepage will be elevated if the interface roughness between layers was roughened. The levees with fine sand at upper layer and coarse sand at lower layer can remarkably reduce the critical seepage gradient. Based on the theory for seepage of multi-layered media the for mula forcalculating the piping development in levee foundation was given and verified by computation by means of 3-D FEM. By using this formula the sand boiling scope at suddenly piping location and the probably continuous developing scouring distance towards upstream can be predicted.