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膨胀土边坡开挖时因干-湿循环作用形成裂隙,导致降雨入渗深层土壤,影响边坡稳定性。针对传统工艺存在生态效果差与使用寿命短等不足,进行了6组兼顾生态和防渗功能的非饱和上细下粗二元结构的边坡排水防渗效果的试验研究。采用亮蓝染色示踪方法直接观测了降雨条件下二元结构水分入渗过程,其结果表明:粗粒层粒径越大,级配越差,越易形成优先渗流通道,难以形成连续的水平渗流场,排水效果差。降雨直接入渗至边坡防护层,增加了其入渗边坡土体失稳的风险。通过监测侧向与底部排水体积,分析结果表明:二元结构具有较好的防渗排水效果,其稳定排水效率和综合排水效率分别介于80%~100%和43%~79%之间,随着粗粒层粒径减小、颗粒级配变好,稳定排水效率呈先减小后增加的趋势,而综合排水效率却呈先增加后缓慢减小的趋势。因此,从排水效果和工程材料造价等角度考虑,认为方案4最优。该研究成果可为南水北调膨胀土边坡治理以及其他工程的边坡防渗问题处理提供技术支撑。
During the excavation of expansive soil slope, cracks develop due to dry-wet circulation, leading to rainfall infiltration into deep soil and affecting slope stability. Aiming at the shortcomings of poor ecological effect and short service life of traditional technology, six groups of experimental studies on slope seepage prevention and drainage of unsaturated coarse upper and lower coarse structures with both ecological and anti-seepage functions were conducted. The bright blue staining method was used to directly observe the infiltration process of water in the binary structure. The results showed that the larger the particle size, the worse the grading, the easier it is to form the preferential seepage channel, and it is difficult to form a continuous level Seepage field, poor drainage effect. The infiltration of rainfall directly into the protective layer of the slope increases the risk of instability of the infiltration slope. By monitoring the drainage volume of the lateral and bottom sections, the analysis results show that the binary structure has better seepage prevention and drainage effects, and the stable drainage efficiency and integrated drainage efficiency are between 80% -100% and 43% -79%, respectively. With the decrease of particle size, the particle size distribution becomes better and the steady drainage efficiency decreases first and then increases. However, the overall drainage efficiency increases first and then decreases slowly. Therefore, from the drainage effect and the cost of engineering materials, etc., consider the optimal program 4. The results of this research can provide technical support for the treatment of expansive soil slope in the South-to-North Water Diversion Project and slope seepage control problems of other projects.