-
抽出处理技术是有效的地下水修复技术之一,该技术具有快速阻断污染物迁移和有效去除地下水中污染物的特点,在国内外应用较为广泛[1-3]。影响地下水抽出效率的因素主要有抽水流量、抽水方式、抽水井数量及其布设位置[2, 4]。确定抽水井位置及数量,需要掌握污染羽的分布、场地水文地质条件及特定抽水流量下单井捕获半径及驻点值[5-6]。JAVANDEL等[7]用复变函数理论定量研究了均匀流态下承压完整井形成的截获带,以解析解形式表示了单井捕获半径及驻点。从地下水势叠加原理出发,GRUBB[8]提出了潜水和承压水含水层中抽水井形成的稳定态捕获半径及驻点的解析表达式,但该公式未考虑抽水引起的降落漏斗、渗漏及入渗补给等因素对表达式的影响,误差较大,较少应用。关于补给条件下捕获半径及驻点的研究成果,迄今鲜有文献报道。对各向异性含水层中存在补给的捕获半径及驻点定量研究,各国学者趋向于采用数值模拟方法[9-10]。截至目前,定量获取单井及多井捕获半径、驻点的方法主要有3种,分别为抽水实验实测法、解析解公式计算法、数值模拟法;3种方法各有优点,又各自存在局限性。解析解计算公式适用于均质、等厚的承压含水层或水位降深相对总的饱和带厚度很小的潜水含水层[7, 11-12];解析解公式计算法简便易行,但针对潜水抽水井捕获半径计算尚未有合适的解析解公式。刘明柱等[13]运用数值模拟方法来获取抽水井捕获半径及驻点;数值模拟法更适用于水文地质复杂条件情况,其精度在于对场地水文地质条件掌握程度[14-17]。抽水实验实测法适用条件广、精度高,但须布设较多监测井,成本较高。本研究分别采用上述3种方法对潜水、承压水不同类型场地抽水井的捕获半径及驻点值进行了计算,以确定不同条件下捕获半径及驻点获取的最优方法,为不同类型场地抽水井捕获半径及驻点获取方法提供参考。
单井捕获地下水污染羽的优化方法
Optimal method of groundwater pollution plume capture by single well
-
摘要: 针对不同抽水井捕获半径及驻点获取方法存在局限性和误差的问题,以潜水、承压水2个类型污染场地为例,分别采用实测法、解析解公式法、数值模拟法3种方法计算单井捕获半径及驻点值;通过对比分析,研究了不同条件下3种方法的局限性及精确度;探讨了不同类型污染场地获取捕获半径及驻点的最适宜方法。结果表明:对于承压水类型,解析解计算值与实际观测值误差较小,为3.2%;对于水位降深相对于含水层厚度不可忽略的潜水类型,解析解计算值与实际观测值误差较大,为80.7%;在充分掌握水文地质条件时,数值模型模拟结果与实际观测误差值不超过10%。因此,当场地水文地质情况符合解析解公式假设条件时,可采用解析解公式法获取单井捕获半径及驻点,否则须利用数值模拟方法或实测法获取相关参数。研究成果为不同类型污染场地选择合适方法获取捕获半径及驻点提供了参考。Abstract: In view of the limitations and errors in the acquisition methods of capture radius and stagnation points of different pumping wells, two types of contaminated sites, such as unconfined aquifer and confined aquifer, were taken as examples. Subsequently, the capture radius and stagnation point of a single well are calculated by using the measurement method, the analytical solution formula method and the numerical simulation method, respectively. Through comparative analysis, the limitations and accuracy of the three methods under different conditions were studied. The optimum methods for obtaining the capture radius and stagnation point of different types of contaminated sites were discussed. The results show that for the type of confined aquifer, a low error of 3.2% between the calculated value of analytical solution and the measured value occurred. For the type of unconfined aquifer, its groundwater level drawdown could not be ignored with respect to aquifer thickness, a relatively high error of 80.7% between the calculated value of analytical solution and the measured value occurred. When the hydrogeological conditions were fully mastered, the error between the numerical model simulation result and the measured value did not exceed 10%. Therefore, when the hydrogeological conditions in the field met the assumed conditions of the analytical solution formula, the analytical solution formula could be used to obtain the capture radius and stagnation point of a single well, otherwise, the numerical simulation or field measurement method should be used to obtain the relevant parameters. This study provides a reference for selecting suitable methods to obtain the capture radius and stagnation point of different types of contaminated sites.
-
Key words:
- pumping test method /
- analytic solution formula /
- numerical simulation /
- capture radius /
- stagnation point /
- optimum
-
表 1 不同方式获取抽水井捕获半径及驻点值的对比
Table 1. Comparison between the capture radius and stagnation points obtained by different methods
场地类型 参数类型 抽水流量/
(m3·d−1)抽水实验
实测值/m解析解公式
计算值/m数值模
拟值/m解析解公式
法误差值/%数值模拟法
误差值/%承压水类型 捕获半径 120 290 293.7 285 1.3 1.7 驻点 120 95 93.5 98 1.6 3.2 潜水类型 捕获半径 60 88 33.3 84 58.4 4.6 驻点 60 55 10.6 50 80.7 9.1 -
[1] 姜烈, 何江涛, 姜永海, 等. 地下水硝酸盐污染抽出处理优化方法模拟研究[J]. 环境科学, 2014, 35(7): 2572-2578. [2] 王燕.硝酸盐地下水污染数值模拟与抽出-处理技术抽水井优化研究[D]. 保定: 河北农业大学, 2014. [3] 蒲敏. 污染场地地下水抽出处理技术研究[J]. 环境工程, 2017, 35(4): 6-10. [4] 万鹏.污染地下水抽出-处理技术的抽水方案优化研究[D]. 北京: 清华大学, 2013. [5] 张艳.污染场地抽出-处理技术影响因素及优化方案研究[D]. 北京: 中国地质大学(北京), 2010. [6] 任增平. 水力截获技术及其研究进展[J]. 水文地质工程地质, 2001(6): 73-77. doi: 10.3969/j.issn.1000-3665.2001.06.026 [7] JAVANDEL I, TSANG C. Capture-zone type curves: A tool for aquifer cleanup[J]. Groundwater, 1986, 24(5): 616-625. [8] GRUBB S. Analytical model for estimation of steady-state capture zones of pumping wells in confined and unconfined aquifers[J]. Groundwater, 1993, 31(1): 27-32. [9] ZLOTNIK V. A Effects of anisotropy on the capture zone of a partially penetrating well[J]. Groundwater, 1997, 35(5): 842-847. [10] BAIR E S, LAHM T D. Variations in capture-zone geometry of a partially penetrating pumping well in an unconfined aquifer[J]. Groundwater, 1996, 34(5): 842-852. [11] SATKIN R L, BEDIENT P B. Effectiveness of various aquifer restoration schemes under variable hydrogeologic conditions[J]. Groundwater, 1988, 26(4): 488-498. [12] KIM J W. Optimal pumping time for a pump-and-treat determined from radial convergent tracer tests[J]. Geosciences Journal, 2014, 18(1): 69-80. doi: 10.1007/s12303-013-0051-x [13] 刘明柱, 陈鸿汉, 胡丽琴, 等. 生物降解作用下地下水中TCE、PCE迁移转化的数值模拟研究[J]. 地学前缘, 2006, 13(1): 155-159. doi: 10.3321/j.issn:1005-2321.2006.01.021 [14] 于虎广. 基于Visual Modflow的曲周县地下水中盐分运移模拟研究[D]. 邯郸: 河北工程大学, 2012. [15] 陈崇希, 王旭升, 胡立堂. 地下水流数值模拟中抽水井水位的校正[J]. 水利学报, 2007, 38(4): 481-485. doi: 10.3321/j.issn:0559-9350.2007.04.016 [16] 张海岛.长治盆地浅层孔隙地下水流数值模拟研究[D]. 邯郸: 河北工程大学, 2017. [17] 白福高, 刘明柱, 刘伟江, 等. 潮白河河道地下水人工回灌包气带水分运移模拟[J]. 环境污染与防治, 2016, 38(6): 88-91. [18] 刘燕, 辛璐君, 郭建青, 等. 抽水实验确定各向异性含水层参数的实例讨论[J]. 勘察科学技术, 2012(6): 5-9. doi: 10.3969/j.issn.1001-3946.2012.06.002 [19] 蒋辉. 基于Aquifer Test的抽水实验参数计算方法分析[J]. 水文地质工程地质, 2011, 38(2): 35-38. doi: 10.3969/j.issn.1000-3665.2011.02.006 [20] 中华人民共和国水利部发布. 中华人民共和国水利行业标准水利水电工程钻孔抽水试验规程: SL 320-2005[M]. 北京: 中国水利水电出版社, 2005.