海岸带咸淡水界面实验研究及数值模拟

发布时间：2018-05-04 09:11

本文选题：海岸带 + 咸淡水界面　；参考：《中国地质大学(北京)》2015年硕士论文

【摘要】：改革开放以后,滨海地区进入高速发展阶段,市场化、工业化程度不断提高,外来人口不断增加,工农业和市政用水需求日益增长,科学评价和合理开发滨海含水层地下水资源成为一个重要的研究课题。20世纪60年代以来,由于滨海地区不合理的开采地下水资源,含水层中地下水位下降,致使淡水水头低于咸水楔形体的水头,咸淡水界面向内陆方向移动。这种在地下水开发利用的影响下,海水向内陆方向迁移的现象称为海水入侵。我国海水入侵现象最早出现于大连市,其后青岛市、莱州市、北海市等地也相继出现海水入侵问题。据统计现今我国主要受灾城市海水入侵总面积已达900 km2。滨海含水层中咸淡水之间的界面形态特征和运移规律是研究海水入侵现象的重要内容。本文建立滨海潜水含水层咸淡水界面实验室模拟实验,采用不同的咸水密度和咸水水头,研究咸淡水突变界面的动态及平衡特征,分析平衡条件下,咸淡水界面向内陆延伸最远距离与咸水水头和咸水密度之间的关系。实验结果表明咸水密度和咸水水头的增大都会导致咸淡水界面向内陆方向延伸最远距离变大,界面形态主要受咸水密度控制,当咸水密度由大变小时,界面由陡峭变缓倾。采用MODFLOW中的SEAWAT模块建立了数值模型模拟实验过程,模型运行结果显示咸水密度是界面形态的主要控制因素,当咸水水位为45 cm时,咸水密度由1.060 g/cm3增大到1.1 g/cm3,咸水边界处淡水排泄口长度由28 cm减小为17 cm,咸淡水界面向淡水边界方向延伸最远距离由21.5 cm增加为50.5 cm,界面由陡峭变缓倾,这与咸水密度是控制咸淡水界面形态的主要因素的实验结果是相符的。抽水导致的海水入侵距离是研究海水入侵问题的核心。文中给出咸淡水界面之上淡水带抽水导致的咸淡水界面升锥高度和界面之后淡水带抽水引起的界面入侵距离的计算公式,经实验结果验证,公式能比较准确的反应实际情况,由于实验中用于计算潜水含水层中淡水流量的水位测压孔距咸淡水界面距离较近,给计算结果带来了一些误差。抽水状态下的数值模型运行结果表明咸水水位是控制抽水导致的咸淡水界面入侵距离的主要因素,当咸水密度恒定为1.050 g/cm3,抽水量为1 m3/d,咸水水位由45 cm升高到46 cm时,界面入侵距离由13 cm增大为27 cm。
[Abstract]:After the reform and opening up, Binhai area has entered a stage of rapid development, with the marketization, the degree of industrialization continuously increasing, the foreign population increasing, and the demand for water for industry, agriculture and municipal water increasing day by day. Scientific evaluation and rational exploitation of groundwater resources in coastal aquifers have become an important research topic. Since the 1960s, groundwater levels in aquifers have declined due to unreasonable exploitation of groundwater resources in coastal areas. The head of fresh water is lower than that of wedge of salt water, and the boundary of salt water moves inland. Under the influence of groundwater exploitation and utilization, sea water migration inland is called seawater intrusion. Seawater intrusion was first found in Dalian, and then in Qingdao, Laizhou, Beihai and other places. According to statistics, the total area of seawater intrusion in the main affected cities in China has reached 900 km ~ 2. The characteristics of interface morphology and migration between brackish and fresh water in coastal aquifers are important for the study of seawater intrusion. In this paper, the laboratory simulation experiment of salt-fresh water interface of coastal diving aquifer is established. Different salt water density and salt water head are used to study the dynamic and equilibrium characteristics of salt-fresh water abrupt interface, and the equilibrium conditions are analyzed. The relationship between the furthest distance of the salt water boundary extending inland and the salt water head and the salt water density. The experimental results show that both the increase of the salt water density and the increase of the salt water head will result in the furthest extension of the salt water boundary towards the inland direction. The interface morphology is mainly controlled by the salt water density. When the salt water density changes from large to small, the interface changes from steep to slow. The numerical model is established by using the SEAWAT module in MODFLOW. The results show that the salt water density is the main controlling factor of the interface, and the salt water level is 45 cm. The density of salt water increased from 1.060 g/cm3 to 1.1 g / cm 3, the length of fresh water outlet at the salt water boundary decreased from 28 cm to 17 cm, and the furthest distance from 21.5 cm to 50.5 cm was increased from 21.5 cm to 50.5 cm. This is consistent with the experimental results that the density of salt water is the main factor controlling the interface morphology of salty and fresh water. The distance of seawater intrusion caused by pumping water is the core of the study of seawater intrusion. In this paper, the formulas for calculating the height of the rising cone of the salt-fresh water interface caused by the pumping of the fresh water zone above the salt-fresh water interface and the distance of the interface invasion caused by the pumping of the fresh water belt after the interface are given. The experimental results show that the formula can reflect the actual situation more accurately. Because the water level pressure hole used to calculate the fresh water flow in the phreatic aquifer is close to the interface of the salt and fresh water in the experiment, some errors have been brought to the calculation results. The operation results of the numerical model under pumping state show that the salt water level is the main factor to control the invasion distance of salt-fresh water interface caused by pumping water. When the salt water density is 1.050 g / cm ~ (-3), the pumping capacity is 1 m3 / d, the salt water level increases from 45 cm to 46 cm. The interfacial invasion distance increased from 13 cm to 27 cm.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P731.2;P641.8

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