极限保土状态下的反滤机制试验研究

提出了反滤系统极限保土状态的概念，分别采用4种不同孔径的钢丝编织网进行粉土反滤试验，研究反滤系统的极限保土状态。试验表明，当滤网孔径O和粉土特征粒径d85的比值等于12时，反滤系统才达到极限保土状态。极限保土状态下的反滤系统，在淹没式出流条件下，经往复水流作用26 h后改为单向水流，水力梯度从3.8逐渐增加到9.1，并在9.1的水力梯度下持续渗透453.25 h，反滤系统仍保持稳定，未发生失稳破坏；在非淹没式出流条件下，水力梯度从5.3逐渐增加到12.7期间，反滤系统保持稳定，但在维持12.7的水力梯度下持续渗透261.83 h后，反滤系统发生失稳破坏。对极限保土状态的研究有助于工程设计中更加合理地确定织物滤层孔径上限，减少淤堵。

Test study on filtration mechanism of silt-net system under limit soil-retained state

Conception of limit soil-retained state was originated. Four kinds of woven steel-wire nets with different opening sizes were adopted in the filtration tests with silt. Test results show that filtration system approached limit soil-retained state when the ratio of the opening size of net filter (O) to the characteristic particle size (d85) of the silt upped to 12. Filtration system under limit soil-retained state kept stable during 26 hours of cyclic flow. And the filtration system still maintained its stability under the unidirectional submersed flow whose hydraulic gradient was increased from 3.8 to 9.1 gradually and maintained at 9.1 for 453.25 hours. Filtration system lost its stability under the unidirectional free flow whose hydraulic gradient was increased from 5.3 to 12.7 gradually and maintained at 12.7 for 261.83 hours. Researches on limit soil-retained state redound to a more reasonable upper limit of filter opening size and less clogging for filtration design.