层状非均质结构包气带入渗过程单相流与两相流数值模拟对比研究

高靖勋; 冯洪川; 祝晓彬; 吴吉春; 吴剑锋; 卫云波; 王水

doi:10.16030/j.cnki.issn.1000-3665.202109011

层状非均质结构包气带入渗过程单相流与两相流数值模拟对比研究

1.
表生地球化学教育部重点实验室/南京大学地球科学与工程学院，江苏南京　210023

2.
江苏省环境工程重点实验室/江苏省环境科学研究院, 江苏南京　210036

基金项目: 国家重点研发计划场地土壤污染成因与治理技术专项课题(2019YFC1804001；2019YFC1804300)；国家自然科学基金项目(42072274；41730856)；江苏省水利科技项目(2020038)

详细信息

作者简介: 高靖勋（1996-），男，硕士研究生，主要从事多场耦合数值模拟研究。E-mail：jxgao1224@163.com

通讯作者: 祝晓彬（1980-），男，副教授，主要从事复杂条件下地下水中污染物迁移转化数值模拟研究。E-mail：zxb@nju.edu.cn

中图分类号: P641.2

收稿日期: 2021-09-15

修回日期: 2021-10-25

刊出日期: 2022-03-15

A comparative numerical simulation study of single-phase flow and water-gas two-phase flow infiltration process in the vadose zone with the layered heterogeneous structure

1.
Key Laboratory of Surficial Geochemistry, Ministry of Education/ School of Earth Sciences and Engineering, Nanjing University, Nanjing, Jiangsu　210023, China

2.
Jiangsu Provincial Key Laboratory of Environmental Engineering/ Jiangsu Provincial Academy of Environmental Science, Nanjing, Jiangsu　210036, China

More Information

Corresponding author: ZHU Xiaobin, zxb@nju.edu.cn

Received Date: 15 September 2021

Revised Date: 25 October 2021

Publish Date: 15 March 2022

摘要

摘要:
包气带水分入渗过程受多种因素的影响。定量研究层状非均质岩性结构和入渗速率对其影响，有助于解决根据不同条件选择单相流模型或水气二相流模型模拟包气带水分入渗过程的问题。结合填埋场等场地地层条件及污废水入渗特征，分别建立了“上细下粗”和“上粗下细”包气带层状非均质岩性结构水分入渗单相流和水气二相流模型，探讨不同层状非均质岩性结构条件下模型的适用性。在“上粗下细”岩性结构模型基础上，进一步探究入渗速率对水气两相运移结果的影响。基于论文模型研究表明：（1）在包气带岩性结构为“上细下粗”的条件下，气相的影响基本可以忽略，可直接采用单相流模型对包气带水分运移进行模拟；在“上粗下细”岩性结构和本次模型设定的底部压力保持不变及污废水泄漏前场地未接受降水入渗补给等条件下，当包气带上下层介质渗透率比值大于16倍时，气相会对水相运移产生明显影响，且下层介质渗透率越小、上下层介质渗透率比值越大，单相流与两相流的运移结果差别越大，需要采用水气二相流模型模拟包气带水分运移。（2）在包气带“上粗下细”岩性结构条件下，入渗速率越大，气相对水流入渗的阻滞作用越明显，此时包气带水分运移模拟应采用水气二相流模型。
- 场地 /
- 层状非均质岩性结构 /
- TOUGH2 /
- 水气二相流 /
- 入渗速率 /
- 包气带
Abstract:
The infiltration process in the vadose zone is affected by many factors. A quantitative study of the influence of the layered heterogeneous lithological structure and infiltration rate on the process of water infiltration in the vadose zone is helpful in selecting a single-phase flow model or water-gas two-phase flow model for simulating the infiltration process in the vadose zone under different conditions. In this study, combined with stratum conditions of landfills and other sites and the infiltration characteristics of polluted or waste water, water infiltration single-phase flow and water-gas two-phase flow models are established under the “upper fine and lower coarse” and “upper coarse and lower fine” layered heterogeneous lithological structures of the vadose zone, in order to discuss the applicability of the models under different layered heterogeneous lithological structures. Based on the “upper coarse and lower fine” lithological structural model, the influence of infiltration rate on the results of water-gas two-phase migration is further explored. The results based on paper models show that (1) under the “upper fine and lower coarse” lithological structure condition of the vadose zone, the influence of the gas phase can be ignored and the single-phase flow model can be used to simulate water migration in the vadose zone. Under the settings of the “upper coarseness and lower fineness” lithological structure, the fixed bottom pressure and no precipitation infiltration before the leakage of sewage and wastewater in this model, gas phase has a significant impact on the water migration when the permeability ratio of the upper and lower media in the vadose zone is greater than about 16 times, and the lower the permeability of the underlying medium and the greater the permeability ratio of the upper and lower media, the greater the difference between the results of the single-phase flow and water-gas two-phase flow. It is necessary to use the water-gas two-phase flow model to simulate the water migration in the vadose zone. (2) Under the “upper coarseness and lower fineness” lithological structure condition of the adose zone, the greater the infiltration rate, the stronger the blocking effect of air on the water infiltration, and the water-gas two-phase flow model should be used to simulate the process of water migration in the vadose zone.
- site /
- layered heterogeneous lithological structure /
- TOUGH2 /
- water-gas two-phase flow /
- infiltration rate /
- vadose zone

HTML全文

图 1 包气带层状非均质岩性结构概念模型

Figure 1.

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图 2 “上细下粗”岩性结构条件下水分入渗52 d水相饱和度分布

Figure 2.

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图 3 “上细下粗”岩性结构交界面上、下观测点气压与水相饱和度变化曲线

Figure 3.

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图 4 “上粗下细”岩性结构条件下水分入渗80 d水相饱和度分布

Figure 4.

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图 5 “上粗下细”岩性结构交界面上、下观测点气压与水相饱和度变化曲线

Figure 5.

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图 6 “上粗下细”岩性结构下水分入渗导致潜水面孔隙水压力变化历时曲线

Figure 6.

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图 7 不同情景下单相流与水气二相流模型水分入渗补给至潜水面所需时间变化曲线

Figure 7.

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图 8 不同情景下“上粗下细”岩性结构界面下方观测点气压与水相饱和度变化曲线

Figure 8.

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图 9 入渗速率q=2×10⁻⁵ m/s时，“上粗下细”岩性结构水分入渗130 d水相饱和度分布

Figure 9.

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图 10 入渗速率q=2×10⁻⁵ ，8×10⁻⁶ m/s时，“上粗下细”岩性结构界面下方观测点气压与水相饱和度变化曲线

Figure 10.

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表 1 非均质介质主要参数^[14]

Table 1. Main hydrogeological parameters of heterogeneous media^[14]

介质	密度/（kg·m⁻³）	渗透率/（10⁻¹²m²）	孔隙度	相对渗透率-饱和度关系曲线 (VG-M模型)				毛细压力-饱和度关系曲线 (VG模型)
介质	密度/（kg·m⁻³）	渗透率/（10⁻¹²m²）	孔隙度	λ	S_lr	S_ls	S_gr	λ	S_lr	S_ls	P_max	1/P₀
粗砂	2 650	30	0.31	0.416	0.06	1	0.05	0.416	0.06	1	5×10⁶	3.0×10⁻⁴
细砂	2 650	8.0	0.35	0.430	0.10	1	0.05	0.430	0.10	1	5×10⁶	2.5×10⁻⁴
亚黏土	2 650	0.16	0.40	0.447	0.15	1	0.05	0.447	0.15	1	5×10⁶	1.0×10⁻⁴
注：λ为经验参数，为残余水饱和度，为饱和水饱和度，为残余气饱和度，P_max为最大吸力，1/为土壤进气值的倒数。

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表 2 不同模拟情景参数设置

Table 2. Parameter settings of different simulation cases

模拟情景设置		渗透率/（10⁻¹²m²）	上下层介质渗透率比值
上层介质（细砂）		8.0	/
情景1	下层介质1 （亚黏土）	0.16	50
情景2	下层介质2	0.20	40
情景3	下层介质3	0.40	20
情景4	下层介质4	0.50	16
情景5	下层介质5	0.80	10
情景6	下层介质6	1.6	5

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