【作者】 孟宪萌；

【导师】 胡和平；

【作者基本信息】 清华大学 ， 水利工程， 2010， 博士

【摘要】 随着工农业迅猛发展、人口的不断增长以及城市化进程的加快,对深层承压水的开采增加,从而导致深层承压水水头下降,人为的加强了浅层地下水与深层地下水的水力联系;受到污染的浅层地下水对深层承压水的安全构成威胁,如何衡量承压含水层受到污染的可能性是迫切需要解决的问题。本文在全面分析和总结目前国内外地下水脆弱性概念、分类和评价方法的基础上,提出将承压含水层顶板处污染物浓度超过最大允许浓度的累计时间作为承压含水层脆弱性指数,并以单井开采条件下承压含水层脆弱性评价为例对承压含水层脆弱性指数的合理性进行了数值验证。该脆弱性指数具有明确的物理意义,对污染物进入承压含水层的过程进行了详细的刻画,能够很好的反映出承压含水层受到污染的可能性大小,减少了人为因素对承压含水层脆弱性评价的影响。运用基于熵权的集对分析模型对济宁市浅层地下水水质进行评价,选出代表性的污染因子,利用MODFLOW和MT3D建立三维地下水流与污染物运移模型,计算承压含水层脆弱性指数;其评价结果与该地区两年后总硬度升高值的分布状况吻合较好,表明了评价结果的合理性,通过与迭置指数法进行对比分析了基于过程模拟的评价方法的优越性。在阐述承压含水层脆弱性评价特点以及分析污染物在越流作用下进入承压含水层物理过程的基础上,构建了基于一维描述的越流区承压含水层脆弱性简化评价方法。对理想条件下单井开采和济宁市承压含水层脆弱性,分别用三维模型模拟的方法和简化的一维模型模拟的方法进行评价,通过对评价结果的对比分析验证了简化评价方法的合理性,该方法适应于缺资料地区的承压含水层脆弱性评价。将蒙特卡罗随机模拟与参数随机化处理相结合,运用频率分析得到单井开采条件下不同脆弱性评价结果对应的可靠度,为风险决策提供依据。通过局部灵敏度分析和Morris法的全局灵敏度分析对基于一维描述的越流区承压含水层脆弱性简化评价方法中的参数进行灵敏度分析。更多还原

【Abstract】 With the rapid development of industry and agriculture, the increasing expansion of population, and the acceleration of urbanization process, the confined groundwater exploitation is steadily increasing, resulting in the decline of groundwater head. When the confined groundwater head is lower than that of the shallow aquifer, the polluted shallow groundwater will recharge the confined aquifer through aquitard, which could lead to the pollution of confined aquifer. Hence, it is very urgent to map the degree of confined aquifer vulnerability to contaminants leaking from shallow aquifer due to confined groundwater pumping in order to realize the confined groundwater protection and sustainable development.In this thesis, based on the review and summarization of the concept, classification and assessment methods of groundwater vulnerability, the cumulative time for the pollutant concentration at the coping of confined aquifer exceeding the maximum allowable level is defined as the confined aquifer vulnerability index. Then the assessment of confined aquifer vulnerability induced by a single pumping well is used to illustrate the rationality of vulnerability index. The confined aquifer vulnerability index has explicit physical meaning and has a detailed description of the process for the pollutant to enter the confined aquifer. The index can clearly express the probability that the confined aquifer is polluted and diminish the effect of the human factor to the assessment of the confined aquifer vulnerability.Shallow groundwater quality in Jining city is evaluated by the set pair analysis model based on entropy weight. Then the representative pollutant is chosen. Three dimensional numerical simulation models of groundwater flow and solute transport are established by MODFLOW and MT3D respectively. Then the confined aquifer vulnerability index is obtained. The results are reasonably consistent with the change of total hardness concentration after 2 years. Through comparison with the results from overlay and index methods, the advantages of the proposed method employing process simulation are analyzed. By analyzing the characteristic of vulnerability assessment and physical process of pollutant penetrating the aquitard, the simplified vulnerability assessment method through the establishment of one dimensional groundwater flow and solute transport models in the aquitard is constructed. Compared by the assessment results of the three dimensional groundwater flow and solute transport models, the simplified method is verified to be rational and especially suitable for the lack data area.As there are some uncertainties in confined aquifer vulnerability assessment, which affect the reliability of assessment results, the reliability of confined aquifer vulnerability assessment results induced by a single pumping well is quantitatively analyzed by randomly generating the most sensitive parameters using Monte Carlo method. The local sensitivity analysis and global sensitivity analysis-Morris screening method are used to analyze the sensitivity of parameters in regional confined aquifer vulnerability assessment.更多还原