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| DOI：10.13522/j.cnki.ggps.2022009 |
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| Effect of Cross Section of Subsurface Drain on Its Performance |
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HAN Han, LI Mingsi, ZHANG Jinhua, LIU Xingshuang, XU Qiang, CHEN Wenjuan
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1. College of Water and Architectural Engineering, Shihezi University, Shihezi 832003, China;
2. Faculty of Science Shihezi University, Shihezi 832003, China
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| Abstract: |
| 【Objective】Subsurface drain is an engineering technology to control groundwater table not exceeding a critical depth. Its performance depends not only on soil properties but also on design parameters. The purpose of this paper is to investigate the impact of geometrical configuration of the drain on its performance in controlling water and salt movement in the soil. 【Method】We compared four cross sections: circular section with an impermeable drain bottom (T1); equilateral triangular section with an impermeable bottom; circular section with an impermeable wing at the drain bottom; equilateral triangular section with an impermeable wing at the drain bottom. All drains were made by metal wire meshes; they were wrapped by non-polyester filament and perforated non-woven geotextile filter layer. The drainage experiment was conducted in soil columns repacked with a sandy soil. Each column was irrigated by 7 L of water. During the experiment, we measured soil water movement around the drain; water flow in the soil was simulated using a MATLAB program. 【Result】The time that water started exiting the outlet of the drain in T2 was 7.45 h ahead of that in T1. Adding an impermeable wing at the bottom of the drain inhibited water exfiltration thereby improving drainage efficiency. It was found that soil moisture content at the bottom of the drain (50 cm deep) in T3 was 17.02%±0.37% lower than that in T1, while that in T4 was 16.62%±0.77% lower than that in T2. T3 drained 119.8 mL of water and 16.76 g of salt more than T1, while T4 increased 119.7 mL water drainage and 18.83 g salt removal than T2. The time that water started exiting the outlet of the drain in T3 was 9.79 h earlier than that in T1, while the starting time for water to exit the drain in T4 was 3.47 h ahead of that in T2. Numerical simulation confirmed that T2 reduced water exfiltration more, especially with an added impermeable wing at the bottom of the drain, and it is hence most effectively in draining water and removing salt. 【Conclusion】Subsurface drain with triangular cross section was more effective in inhibiting water exfiltration, especially after adding an impermeable wing to its bottom. |
| Key words: subsurface drain; unsaturated soil; draining water and salt; reclamation of saline-alkali land |
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