盐田上填海造陆区水盐运移过程研究

发布时间：2018-07-10 03:32

本文选题：填海造陆 + 盐田　；参考：《大连理工大学》2015年硕士论文

【摘要】：填海造陆是人类开发利用滨海地区的重要方式,也是人类拓展生存空间和生产空间的重要手段。但是填海造陆在缓解土地需求矛盾的同时,也给回填区带来了盐渍化的危害,盐渍土给回填区的生态建设带来了地表绿化困难、地下设施腐蚀、路基稳定破坏等问题。近些年,在国家政策和经济利益的驱使下,大量填海工程直接建立在盐田之上,回填后地下水完全浸渍盐田土,使其中的盐分溶解扩散,并通过蒸发作用不断向上层积聚,这在一定程度上会加剧回填区的地表盐渍化。因此,研究盐田上填海造陆区的水盐运移规律对滨海生态建设具有重要的指导意义。本文以盐田上的填海造陆工程为研究对象,在调查其盐渍化危害的基础上,开展潜水蒸发驱动下的土壤水盐运移规律分析及调控研究。主要研究内容和结论如下：(1)通过实地考察气候条件相近的典型填海工程,初步分析盐田对建立在其上的填海造陆工程的危害。结果表明,回填区表层的土壤含盐量与附近盐田的土壤含盐量具有一致性,且年份的推移使其含盐量越接近。土壤颗粒级配对水盐运移的影响是基于不同粒径土壤对水盐的渗透能力和土壤颗粒吸附能力的差异。(2)通过室内试验,模拟不同颗粒级配下土壤的淋洗过程,以分析不同颗粒级配对土壤中水盐运移的影响。结果表明,细粒土含量越大,其对土体渗透系数的影响程度就越大,即细粒土含量的减少,使土体达到稳定渗透状态的时间缩短、渗透系数增大,且使土体渗透系数增加的幅度降低。同时土壤渗漏液电导率和渗透系数的变化过程也随着细粒土含量的不同而呈现出不同的变化规律。(3)通过室内试验,模拟多种变化环境下的地表积盐过程,以分析不同地下水矿化度和盐田土对积盐过程的影响。结果表明,当地下水矿化度较低时,土柱中的盐分呈现出从下层迁移到上层的规律,而当地下水矿化度较高或存在盐田土时,下层迁移走的盐分得到了补给,这将进一步加剧盐分的上移和表聚。随着矿化度环境的提高,地下水对上层填土积盐的影响权重也相应提高,而各土柱中盐田土的含盐量是相对固定的,所以盐田土对上层填土盐分累积增量的影响逐渐减弱,使其盐分增幅逐渐降低,且盐分增加速率达到稳定状态的时间提前。土壤盐分类型从CaSO4型转变为NaCl型。(4)以滨海区生态建设的可持续发展为导向,分析回填区的盐分来源及其影响因素,提出有针对性的改善方案。海水和地下水是回填区盐分补给的主要来源,其次是地表径流和盐田,其中盐田在回填初期影响最大。气候因素与地形地貌是影响盐田等高含盐层形成的主要外界条件。针对盐田等高含盐土层,主要采取物理措施、化学措施、工程措施、生物措施来改善盐田土的含盐量,降低其对填海造陆区的盐渍化危害。
[Abstract]:Reclamation is an important way for human beings to develop and utilize coastal areas, and it is also an important means for human beings to expand their living space and production space. However, reclamation not only alleviates the contradiction of land demand, but also brings salinization harm to backfill area. Salinized soil brings problems such as surface greening difficulty, underground facilities corrosion and subgrade stability damage to ecological construction of backfill area. In recent years, driven by national policies and economic interests, a large number of reclamation projects have been built directly on salt fields. After backfilling, groundwater has been completely impregnated in salt soil, resulting in the dissolution and diffusion of salt in the soil, and the accumulation of salt to the upper layer through evaporation. To some extent, this will aggravate the salinization of the backfill area. Therefore, it is of great significance to study the law of water and salt migration for coastal ecological construction. On the basis of investigation of salinization hazards, the study on the regulation and regulation of soil water and salt migration driven by phreatic evaporation is carried out in this paper, taking the reclamation and land reclamation project in salt fields as the research object and on the basis of investigating its salinization hazards. The main research contents and conclusions are as follows: (1) through field investigation of typical reclamation projects with similar climatic conditions, the harm of salt fields to reclamation and land reclamation based on salt fields is preliminarily analyzed. The results show that the salt content in the surface layer of the backfill area is consistent with that in the nearby salt field, and the year goes by makes the salt content closer. The effect of soil particle gradation on water and salt migration is based on the difference of soil permeability to water and salt and the adsorption ability of soil particles. (2) the leaching process of soil under different particle gradation is simulated through laboratory experiments. The effect of different particle gradation on water and salt migration in soil was analyzed. The results show that the greater the content of fine-grained soil, the greater its influence on the soil permeability coefficient, that is, the decrease of fine grained soil content shortens the time of reaching stable permeability state and increases the permeability coefficient. And the increase of soil permeability coefficient is reduced. At the same time, the change process of conductivity and permeability coefficient of soil leakage fluid is different with the content of fine-grained soil. (3) through laboratory experiments, the process of surface salt accumulation in various changing environments is simulated. The effects of different groundwater salinity and salt-field soil on the salt accumulation process were analyzed. The results show that when the salinity of groundwater is low, the salt in the soil column moves from the lower layer to the upper layer, but when the salinity of groundwater is high or the salt soil exists, the salt of the lower layer is recharged. This will further increase the upward movement of salt and surface aggregation. With the increase of salinity environment, the influence weight of groundwater on the salt accumulation of the upper soil is increased accordingly, and the salt content of the saline soil in each soil column is relatively fixed, so the effect of salt field soil on the accumulation of salt in the upper filling gradually weakens. The increasing rate of salt content decreased gradually, and the time of salt increasing rate reaching stable state was advanced. The salt type of soil changed from CaSO4 type to NaCl type. (4) based on the sustainable development of ecological construction in coastal area, the source of salt in backfill area and its influencing factors were analyzed, and the corresponding improvement scheme was put forward. Seawater and groundwater are the main sources of salt recharge in backfill area, followed by surface runoff and salt field. Climatic factors and landform are the main external conditions that affect the formation of salt beds. Physical, chemical, engineering and biological measures are adopted to improve the salt content and reduce the salinization harm to the reclaimed land.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S156.41

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