【摘要】 选取鲁北平原区浅层粉土、浅层咸水和大气降水为供试材料,进行室内雨水-咸水驱替试验,研究驱替过程中的含水介质渗透性变化特征,探讨内陆浅层咸水区水动力、水文地球化学过程对含水层渗透性变异影响.试验结果表明:雨水驱替咸水饱和土柱过程中,随雨水注入,盐分突变,渗透系数由开始的6.49×10-4 cm/s最终降至2.28×10-4 cm/s,并维持相对稳定;第188天后咸水再次驱替土柱,且完全穿透土柱后,含水介质孔隙度由开始的43.02%降至39.73%;在雨水驱替过程中,驱替液黏滞性变化是影响渗透系数变化的因素之一.研究认为,内陆咸水区含水介质黏土矿物含量高,水化学与水动力学条件发生变化,Ca/Mg-Na的离子交换作用、黏粒大量膨胀和释放、扩散引起孔隙度降低是造成含水介质的渗透性下降的主因,咸雨水驱替过程中渗透性的变化具有不可逆性.含水介质水文地质参数的变异对于内陆浅层咸水形成和演化有重要影响.更多还原

【Abstract】 Shallow silt, shallow salt water and atmospheric precipitation, all present in the North Shandong Plain, were selected as materials for this study. Variations in the permeability characteristics of an aquifer medium caused by shallow salt groundwater were studied in laboratory rain-saltwater displacement experiments. We also explored variations in the permeability coefficient of an inland shallow saltwater region attributable to hydrodynamic and hydrogeochemical processes. The experimental results showed that the initial value of the permeability coefficient was 6.49×10-4 cm/s. When salt water was displaced by rain in the saturated soil column, by injecting water and altering the salinity, the final value dropped to, and stabilized at around, 2.28×10-4 cm/s. After 188 days, salt water in the soil column was displaced again and, after adequately penetrating the soil column, the initial aquifer medium porosity fell from 43.02% to 39.73%. It is important to note that the liquid viscosity caused a decrease in aquifer medium permeability during the process of rainwater displacement. Previous studies have suggested that the clay mineral content of the aquifer medium is high in inland salt water zones. As the hydrochemistry and hydrodynamics in the aquifer medium changed in this study, the porosity decreased because of Ca/Mg-Na ion exchange processes, and massive clay expansion occurred because of release and diffusion. Meanwhile, the decreased permeability in the aquifer medium was the result of weakened porosity. The process of salt-rainwater displacement was irreversible because of the change in permeability. This study shows that variations in the hydrogeological parameters of the aquifer medium can have an important influence on the formation and evolution of shallow salt water in inland regions.更多还原