非饱和导排结构控制降雨入渗的边坡物理模型试验

膨胀土渠坡失稳是影响南水北调中线供水工程安全性的重要因素之一,而对其边坡进行防渗处理是解决膨胀土边坡失稳的有效途径。针对传统边坡防渗处理方法(面板与土工布覆盖等)存在生态功能弱以及使用寿命短等不足,开展了非饱和导排结构的边坡防渗效果的物理模型试验研究。利用土壤剖面负压动态监测数据,采用非饱和渗流理论,在不同降雨强度与不同初始含水量条件下,对比分析了两种非饱和导排结构即细/粗粒二元结构和粗粒单一结构,控制降雨入渗边坡的效果。研究结果表明:在降雨强度为4.18×10-4 cm/s的情况下,二元结构能有效阻止降雨入渗;且细粒层初始含水量越低,其储水能力越强,二元结构控制降雨入渗的效果相对越好。在降雨强度为1.72×10-4,4.18×10-4,4.97×10-4 cm/s的情况下,粗粒层单一结构对降雨入渗边坡均具有一定的控制作用,但有5.6%~10.7%的降雨从模型底部排出,存在入渗风险。总体上,从排水–渗流控制效果与生态功能角度考虑,二元结构明显优于单一结构。研究成果可为解决南水北调膨胀土边坡以及其它工程边坡的渗流控制问题提供技术支撑。

Physical model tests on slopes with control of infiltration by unsaturated drainage structures

The instability of expansive soil slope is vital to the security of water supply in the Middle Route project of South-to-North Water Diversion. Anti-seepage control is considered as an effective method to deal with the instability problem of expansive soil slope. Based on the weak ecological function and short life of the traditional methods to deal with the drainage-seepage phenomenon of slopes, the unsaturated drainage structures are introduced to control rainfall to infiltrate into slope soil. Then two unsaturated drainage structures, i.e., fine/coarse grain soil layers (dual-structure) and coarse layer (single-structure) are chosen. The anti-seepage effects of the both structures on the slope in five rainfall tests are investigated. The results show that: (1) The dual-structure can effectively prevent rainfall from infiltrating into the slope, without leakage at the bottom of the expansive soil in the experiment with rainfall intensity of 4.18×10^-4 cm/s. When the initial soil water content of the fine grain layer is lower with a strong storage capacity, the anti-seepage effect is better. (2) The single-structure can protect the expansive soil slope at a certain extent, with the rainfall intensity of 1.72×10^-4, 4.18×10^-4 and 4.97×10^-4 cm/s, however, 5.6%~10.7% of the total rainfall flows out at the bottom of the expansive soil, which indicates the single-structure leakage risk. In a word, the anti-seepage effects of the dual-structure on the slope are better than those of the single-structure. This study is helpful to dealing with the expansive soil slope in the Middle Route project of South-to-North Water Diversion.