【作者】 张晓辉；

【导师】 郑西来；

【作者基本信息】 中国海洋大学 ， 环境工程， 2006， 硕士

【摘要】 咸淡水过渡带是一个从高盐度咸水到低矿化地下水的狭长带。咸淡水过渡带含水介质水敏性的存在具有双重意义:第一,对于咸水入侵地区,这一性质会使得含水介质的渗透性发生不利于地下咸水恢复的变化,由于含水介质渗透性的大幅度下降,单纯的注入淡水来驱替咸水变得极为困难;第二,由于水敏性的存在,使得防止咸水入侵有了新的方法和思路。因此,对咸淡水界面含水介质水敏性的研究具有重要理论意义和应用价值。本研究在现场调查的基础上,分别采集青岛石老人海水、大沽河河水、海水入侵区的含水介质,通过大量的室内柱状试验和批量试验,弄清含水介质在不同水化学和水动力条件下颗粒释放、运移和沉积的动力学过程,掌握含水层水化学变化、颗粒释放、运移、沉积和渗透性变化的内在有机联系,为咸水入侵的定量评价和防治提供科学的依据。研究结果表明:(1)流体流动速率越大,水动力也越大,细微颗粒就越容易发生运移。在相同水动力条件下,水动力作用对渗透性的影响与溶液的离子强度有关,溶液离子强度越高,越不容易引起颗粒释放。批量试验为了防止水动力释放而确定的振荡频率不能超过150次/min,土柱试验中确定的临界进水流速为21 mL/min。(2)批量试验中将振荡频率设置在150次/min,得到影响颗粒释放的临界盐浓度为0.06±0.005 mol/L;在土柱试验中保持进水流速为1.5 mL/min,得到颗粒释放的临界盐浓度在0.06 mol/L附近。两者所得结果基本吻合。释放出的颗粒主要由伊利石、高岭石和绿泥石等非膨胀性的粘土矿物组成。(3)批量试验和土柱试验证明在强酸性条件下,颗粒释放时间短,释放累积量少;而在强碱性条件下,颗粒释放时间长,颗粒释放累积量最多;中性条件下颗粒释放时间和颗粒释放累积量值居中,这说明在相同水动力条件下,高pH值时的颗粒释放倾向要远远大于低pH值时的情况。虽然在地下水环境中pH值的变化范围是6-8,可调范围不大,但是根据试验所得碱性环境能够增强颗粒释放的结果,我们可以在地下水pH值允许范围内适当提高pH值,使含水介质中颗粒释放达到最大量,以此提高含水层的水敏性,降低咸淡水界面上含水介质的渗透性,以获得理想的天然或人工地下防渗带,防止咸水入侵的发生。更多还原

【Abstract】 The saline-freshwater interface is a transition zone from saline water to freshwater. The existence of the water sensitivity at the interface has double significances: firstly, water sensitivity makes the restoration of the permeability of the porous media difficult due to simply injecting fresh water to flush saline water. Secondly, the existence of water sensitivity presents new methods to prevent saline water intrusion. Therefore, it has significant meaning and applied value to study the water sensitivity of the porous media at the saline-freshwater interface.Based on the geohydrological investigation in the fields, seawater, freshwater and sand samples from the saline water intrusion zone were taken to conduct the batch experiments and column experiments. The aims of these experiments were to discuss the dynamics of particle detachment, migration and redeposition under different water hydraulic and chemical conditions at saline-freshwater interface, learn the relationship between the permeability change and the migration and redeposition of the detached particles, supply the scientific dependence for the assessment and prevention of the saline water intrusion. The results show:(1) The faster the fluid velocity, the bigger the effect of the hydraulic is. Thus the fines can easily migrate. Under the same hydraulic conditions, the effect of hydraulic on permeability is related to the critical ionic strength of the solution. The higher the critical ionic strength, the more difficult the fines are released. In the batch experiment, the shaking frequency was not beyond 150 times/min in order to prevent hydrodynamiclly induced particles. In the column experiment the critical influent velocity was 21 mL/min.(2) In the batch experiment when the shading frequency was set in the 150 times/min, the critical salinity concentration caused the particles更多还原