水生植物根系作用下土工合成材料膨润土垫生态防渗机理

GCL may be good for laky ecological effect when it is used for lakebed seepage prevention，which is an ideal impervious material. But at present the related theoretical research falls behind the engineering practice seriously, which hindered the use of this technology. Based on the new concept of ecological seepage control, the application project research systematically the ecological characteristics of lake environment and the anti-seepage performance of GCL through a lot of model experiment, indoor test and numerical simulation and theoretical analysis. The interaction mechanism between GCL and hydrophytes, water quality is revealed, a perfect ecological seepage control structure system is built. The effect law of GCL on the growth of hydrophytes is studied through model test compared with the geomembrane and compacted clay. The biology indexes of hydrophytes, such as height, density and biomass, are researched. The water quality, such as COD、 NH3-N、TP、TU, are probed considering different impervious material and hydrophytes. The effect of GCL on lake ecology is evaluated. Combined with indoor test and numerical simulation, the variation of the GCL permeability is studied under normal root and rotten root state. The relationship is established between the permeability of GCL and penetrable root diameter, numbers and root area ratio, hydrophytes spacing, the thickness of the overlying soil and the rot degree of roots. The research results can lay the solid theoretical basis for the promotion of the ecological seepage control technology based on GCL, which is of great significance for saving water and protecting the ecological environment.

土工合成材料膨润土垫（GCL）用作湖底防渗可兼顾湖泊生态效果，是理想防渗材料。但目前理论研究落后于工程实践，严重阻碍了该技术应用。本项目基于生态防渗新理念，采用模型与室内试验、数值模拟及理论分析等方法，系统研究GCL对湖泊生态特征的影响和GCL的防渗性能，揭示GCL与水生植物、水质相互作用机理，以期构建完善的生态防渗结构体系。内容包括：通过大型模型试验，对比土工膜和压实黏土，研究GCL对水生植物高度、密度、地上及地下生物量等生物指标及对水体化学需氧量、氨氮、总磷、浊度等水质指标的影响规律，量化评价GCL对湖泊生态的影响；采用室内试验与数值模拟方法，研究正常根系与腐烂根系状态GCL渗透性的变化规律，探求GCL渗透性能与穿透根系直径、数量、穿透根的面积比、植物间距、覆土厚度、腐烂根系状态等因素的关系。研究成果将为GCL生态防渗技术应用奠定坚实的理论基础，为节约水资源和保护生态环境作出积极贡献。

针对土工合成材料膨润土垫（GCL）在用于湖底防渗过程中遇到的湖泊的生态效果与湖底GCL的防渗效果等问题，本项目主要研究了GCL与水生植物、水质相互作用机理。通过模型试验，对比土工膜和压实粘土，研究了GCL对水生植物生长影响，分析了不同防渗材料对水质的影响。通过室内渗透试验，研究了不同围压，不同根系直径，不同植物类型及根系是否腐烂条件下，GCL试样的渗透系数，得到不同植物根系对GCL渗透性能的影响规律。通过数值模拟有限元分析，对比分析了GCL失效前后防渗效果。研究结果表明：土工合成材料膨润土垫（GCL），土工膜和压实粘土对三种水生植物（再力花，芦苇，香蒲）的出芽率影响不大，但GCL对三种水生植物的生长影响较其它两种防渗材料显著，明显促进植物的生长。铺设GCL的试验池的水质溶解氧的含量均高于未铺设GCL试验池中水质溶解氧含量；而氨氮和总磷含量均低于未铺设GCL试验池中水质含量。随着围压增大，三种水生植物根系穿透GCL的渗透系数均随之减小。在植物根系直径较小时,GCL仍有较好防渗性能。在同一围压下，随着植物根系穿透GCL的直径增大，渗透系数会随着增大。当再力花，芦苇和香蒲穿透GCL的直径分别大于等于11.04mm，8.18mm和8.09mm时，渗透系数可达到10-8m/s。同样直径的根系，根系腐烂后GCL的渗透系数更大。当再力花，芦苇和香蒲腐烂根系直径大于等于10.28 mm，8.07mm和6.91mm时,GCL渗透系数可达到10-8m/s。渗透系数曲线出现“突变”，斜率显著增大，GCL出现渗漏。研究成果表明GCL用于湖底防渗，对于植物景观和维护水质有很好的效果。但水生植物生长到一定的直径，为了防止GCL防渗性能的失效应采取收割等方法确保GCL的防渗性能。