细砂层埋深对堤基管涌影响的试验研究

不同土层结构的堤基，其管涌发生和发展的情形不同。以前的研究多集中于双层堤基的情况。事实上，含夹砂层堤基中，位于砂砾石层内的细砂层会对堤基管涌的发生产生重大影响，并且这些影响随细砂层在砂砾石层中的位置不同而不尽相同。利用室内砂槽试验，模拟当细砂层位于砂砾石层内部不同深度时含夹砂层堤基管涌的发展过程，研究细砂层埋深对 堤基管涌的影响。试验结果表明，细砂层埋深存在一个临界深度，当细砂层埋深较浅时，堤基的临界水力梯度较小，易于发生管涌，且管涌发生以后，堤基被侵蚀的速率较大，出砂较多；堤基破坏的临界水力梯度随着细砂层埋深的增加而增大，当细砂层埋深大于临界埋深时，堤基的临界水力梯度基本不变，同时堤基抵抗管涌破坏的能力较强，其破坏形式与双层堤基 相类似。

Experimental research on piping development considering buried depth of fine sand

Different foundation structure has different types of embankment piping. Previous researches have always focused on two-stratum dike foundation. In fact, the buried depth of fine sand has a significant influence on the piping development of foundations with fine sand. A series of simulated experiments is carried out to study the development process and mechanism of three-stratum dike foundations when the buried depth of fine sand changes. The results of experiments indicate that the burial depth of fine sand has a critical value. When the burial depth of fine sand is small, the critical hydraulic gradient is low and it’s easy to cause piping. After the occurrence of piping, more sand pours out of the embankment, and it leads to faster erosion. The critical hydraulic gradient increases as the buried depth of fine sand increases. While the buried depth is greater than the critical depth, the buried depth has almost no influence on the critical hydraulic gradient; meanwhile, the foundation has a strong ability to resist piping; its development of piping is similar to two-stratum dike foundation.