土层结构对管涌发展影响的试验研究

不同的土层结构对管涌的发生发展有着很大影响,对3种典型的土层结构进行了管涌发展的砂槽模型试验,观察并分析了管涌发生、发展的机理和过程。试验结果表明,双层堤基的砂砾石表面夹一层很薄的无黏性粉细砂时,管涌破坏前出水口的流量很小,临界水力梯度也较小,管涌破坏发生后通道发展速度很快,较短的时间内就会贯通,管涌破坏的机理与双层堤基不同；而在砂砾石层一定深度内夹有一层粉细砂将使堤基管涌破坏的临界水力梯度大大提高,然而一旦管涌破坏发生后涌砂量和侵蚀速率将很大,形成的通道深度较大,若不及时采取有效措施,当通道规模发展到一定程度后,通道上部会发生塌落而使堤坝产生溃口,进而使堤坝溃决。

Experimental study on piping development considering effect of foundation structure

The foundation structure has a significant influence on the evolution of piping. A series of experiments on three typical foundation structures are carried out to investigate the process and mechanism of piping using a self-designed apparatus. The results indicate that a thin layer of cohesionless silty sand paved on the surface of the sandy gravel layer reduces the discharge in the outlet before erosion, meanwhile the critical hydraulic gradient is low and the developing speed of the piping channel is very fast. The piping mechanism in this foundation structure is different from that in two-stratum dike foundation. When the silty sand is laid at the certain depth of the sandy gravel layer, the critical hydraulic gradient increases greatly. Once the foundation is eroded, the erosion mass and the erosion rate will be very large, and the channel will be deep. The foundation will burst for the development of the channel if no effective measures are taken.