基于可控性生态减渗目标的河床底质重构技术研究

生态减渗技术对发挥河流生态效益和减少水资源浪费具有重要意义。为研究适用于渗漏河道的河床底质生态减渗方案,开展变水头渗透试验与模型入渗试验探究了复合土减渗效果和入渗特性,结合各河道条件提出了不同的减渗配比及断面结构方案,并利用GeoStudio SEEP/W软件对不同方案下的渗流状况和渗漏量进行了模拟计算。结果表明：复合土减渗效果主要受掺料类型和掺量影响,掺入15%纳基膨润土的复合土在1m水头作用下,浸润锋经39天运移至复合土减渗层底部,56天内累计入渗量为11.1cm,减渗效果较好,可满足工程减渗需求；GeoStudio SEEP/W模拟显示,复合土减渗方案在高效减渗的同时保留有较高的侧向补水给能力,河流水位在0.3m~2m变化,两种典型方案的渗流损失量可降低37.54%~48.06%和75.34%~82.82%。

Research on Riverbed Sediment Reconstruction Technology Based on Controllable Ecological Seepage Reduction Targets

Rivers located in groundwater overexploitation areas provide the functions of maintaining ecological water levels and supplying groundwater by infiltration. Thus, it is important to study riverbed substrate reconstruction technology to maintain the vertical connectivity of the riverbed by controlling seepage. In this study, we obtained the materials to reconstruct the riverbed sediment by mixing riverbed sediment from the North China Plain with various types of bentonite in different ratios. The infiltration characteristics of the reconstituted substrate were then explored using variable water head infiltration tests and model infiltration tests. Next, we proposed different seepage reduction ratios and developed three structural schemes (Scheme 1: 100mm seepage reduction layer with 9% sodium bentonite; Scheme 2: 150 mm seepage reduction layer with 15% sodium bentonite; Scheme 3: 200mm seepage reduction layer with 18% sodium bentonite) based on river conditions. Finally, GeoStudio SEEP/W software was used to simulate the seepage conditions and the seepage reduction effects of the three schemes were analyzed. Results show that permeability coefficient reduction by the composite sediment can be controlled by changing the type and content of bentonite, and two target permeability coefficients (< 1×10-6 cm/s and < 1×10-7 cm/s) were achieved. When the content of sodium bentonite in the composite soil was 15% and the infiltration head was 1 m, the infiltration front moved 15 cm in 39 days and the cumulative infiltration water volume in 56 days was 11.1 cm. The composite sediment was better at reducing seepage and simulation results indicate that the three schemes all effectively reduced the seepage flow. When the river water level rose from 0.3m to 2m, seepage loss was reduced by 55.8%-68.8% in Scheme 1, 91.5%-94.3% in Scheme 2, and 94.8%-96.5% in Scheme 3. Scheme 1 is suitable for rivers with low infiltration requirements and high groundwater recharge requirements, Scheme 3 is suitable for rivers with high infiltration requirements and high water levels, and Scheme 2 has the widest scope of application. Our results provide reference and basis for ecological water replenishment and infiltration reduction restoration work in the North China Plain.