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Article

Analytical Solutions of Vertical Airflow in an Unconfined Aquifer with Rising or Falling Water Table

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Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
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Beijing Institute of Hydrogeology and Engineering Geology, Beijing 100195, China
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Yellow River Engineering Consulting Co., Ltd. (YREC), Zhengzhou 450003, China
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School of Earth Sciences and Resources, China University of Geosciences, No. 29 Xueyuan Road, Haidian District, Beijing 100083, China
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Ministry of Education Key Laboratory of Groundwater Circulation and Evolution, China University of Geosciences, No. 29 Xueyuan Road, Haidian District, Beijing 100083, China
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Authors to whom correspondence should be addressed.
Academic Editor: Marisa Almeida
Water 2021, 13(5), 625; https://doi.org/10.3390/w13050625
Received: 8 December 2020 / Revised: 17 February 2021 / Accepted: 20 February 2021 / Published: 27 February 2021
The rise and fall of the groundwater level can drive air flow in the vadose zone. In turn, the air flow can interact with the water flow. When the unconfined aquifer is covered by a low-permeability media, the coupling of the water flow and the air flow is more obvious. In this study, a conceptual model is established for coupling of air flow and water flow in the vadose zone in response to rapid fluctuations of the water table. Water injection and drainage experiments are conducted in a double-layered sand column with a thick layer (80.5 cm) of coarse sand and a thin layer of fine sand as a low-permeability cap. Different cap thickness (2 cm, 5 cm, 7.5 cm) and different thickness of the vadose zone (30 cm, 40 cm) are set for the experiments. Negative pressure (NP)/positive pressure (PP) of the air in the vadose zone is observed in the drainage/injection experiments, with higher pressure in experiments of thicker cap layer. In each experiment, NP or PP increases rapidly to reach a maximum in the early stage, and gradually becomes zero in the late stage. Analytical solutions on three subdivided stages indicate the permeability and thickness of the cap layer, as well as permeability and porosity of the media in the vadose zone are the key controlling factors on the process of coupling of air flow and water flow. The solutions also reveal the formation mechanism of air pressure in the vadose zone with a low-permeability cap. This study has both theoretical significance and engineering applications. View Full-Text
Keywords: vadose zone; vertical airflow; low-permeability; analytical solution; dynamics vadose zone; vertical airflow; low-permeability; analytical solution; dynamics
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MDPI and ACS Style

An, R.; Dong, P.; Wang, J.-Z.; Zhang, Y.; Song, X.; Wan, L.; Wang, X.-S. Analytical Solutions of Vertical Airflow in an Unconfined Aquifer with Rising or Falling Water Table. Water 2021, 13, 625. https://doi.org/10.3390/w13050625

AMA Style

An R, Dong P, Wang J-Z, Zhang Y, Song X, Wan L, Wang X-S. Analytical Solutions of Vertical Airflow in an Unconfined Aquifer with Rising or Falling Water Table. Water. 2021; 13(5):625. https://doi.org/10.3390/w13050625

Chicago/Turabian Style

An, Ran, Pei Dong, Jun-Zhi Wang, Yifan Zhang, Xianfang Song, Li Wan, and Xu-Sheng Wang. 2021. "Analytical Solutions of Vertical Airflow in an Unconfined Aquifer with Rising or Falling Water Table" Water 13, no. 5: 625. https://doi.org/10.3390/w13050625

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