范严伟, 王延祥, 朱鹏程, 杨志伟. 竖管地表滴灌下风沙土稳定入渗率与湿润体估算模型[J]. 农业工程学报, 2021, 37(7): 103-111. DOI: 10.11975/j.issn.1002-6819.2021.07.013
    引用本文: 范严伟, 王延祥, 朱鹏程, 杨志伟. 竖管地表滴灌下风沙土稳定入渗率与湿润体估算模型[J]. 农业工程学报, 2021, 37(7): 103-111. DOI: 10.11975/j.issn.1002-6819.2021.07.013
    Fan Yanwei, Wang Yanxiang, Zhu Pengcheng, Yang Zhiwei. Estimation model for steady infiltration rate and wetting pattern of aeolian sandy soil under vertical pipe surface drip irrigation[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(7): 103-111. DOI: 10.11975/j.issn.1002-6819.2021.07.013
    Citation: Fan Yanwei, Wang Yanxiang, Zhu Pengcheng, Yang Zhiwei. Estimation model for steady infiltration rate and wetting pattern of aeolian sandy soil under vertical pipe surface drip irrigation[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2021, 37(7): 103-111. DOI: 10.11975/j.issn.1002-6819.2021.07.013

    竖管地表滴灌下风沙土稳定入渗率与湿润体估算模型

    Estimation model for steady infiltration rate and wetting pattern of aeolian sandy soil under vertical pipe surface drip irrigation

    • 摘要: 为了量化解决竖管地表滴灌过程中滴头流量与竖管结构参数(竖管直径和竖管埋深)、土壤湿润体与植物根系的匹配问题,该研究通过12组竖管内积水(2 cm水头)入渗试验(9组率定,3组验证),测定不同竖管直径(8.8、10.6、12.6、14.2 cm)和竖管埋深(15、20、25 cm)条件下风沙土累积入渗量变化过程,并采用Philip入渗模型拟合。结果表明:竖管直径一定时,稳渗率随埋深的增大而减小,竖管埋深一定时,稳渗率随管径的增大而增大,稳渗率与竖管直径和竖管埋深之间符合幂函数关系(决定系数R2>0.99),幂函数指数分别为2.01和-0.64。利用所建稳定入渗率估算式确定与竖管结构参数相匹配的滴头流量(保证竖管内无积水),设计9组竖管地表滴灌室内试验(7组率定,2组验证),观测不同滴头流量(0.9、1.2、1.5 L/h)、竖管直径(10.6、12.6、14.2 cm)和竖管埋深(15、20、25 cm)条件下风沙土湿润锋运移过程,并进行幂函数拟合,发现滴头流量对垂直向下湿润锋运移距离显著,滴头流量越大,垂直向下湿润锋运移距离越大,而水平方向和垂直向上湿润锋运移距离差异较小;在3个方向上湿润锋运移距离均随竖管直径的增大而减少;随竖管埋深增加,垂直向上和垂直向下湿润锋运移距离均有所减小,但水平方向湿润锋运移距离变化很小。确定了灌溉水到达竖管底孔所需时间计算式,在此基础上,构建了包括滴头流量、竖管直径、竖管埋深和灌水时间在内的竖管地表滴灌湿润体预测模型,验证所建模型的可靠性,平均绝对误差和均方根误差平均值分别为0.74和0.92 cm,纳什效率系数均大于0.91,说明预测效果良好。该研究所建稳定入渗率和湿润体预测模型对于竖管地表滴灌优化设计具有重要意义。

       

      Abstract: Vertical-pipe drip irrigation is one of the most efficient state-of-the-art techniques for water-saving and temperature conservation, thereby alleviating the combined stress of drought and high temperature in sand-fixing plant seedlings. In terms of long-term engineering, it is necessary to explore the infiltration characteristics of aeolian sandy soil under vertical-pipe drip irrigation. Furthermore, the discharge rate of the drip system is required less than the stable infiltration rate of water in a critical depth, in order to meet the requirement of no flooding seedlings when the emitter is combined with the vertical pipe. In this study, a ponding infiltration test was carried out using a 2 cm constant head in the field to investigate the variation process of cumulative infiltration of aeolian sandy soil under different buried depths and diameters of vertical pipe. A Philip infiltration model was established to fit the data. 9 treatments and 3 control tests were included in the infiltration experiment. Specifically, the diameter of the vertical pipe was designed with the levels of 8.8, 10.6, 12.6, and 14.2 cm, while the buried depth was set at 15, 20, and 25 cm. The results show that the stable infiltration rate of Philip model increased as the diameter of vertical pipe increased, and decreased with the increase of buried depth. A power function relationship (R2> 0.99) was followed between the steady permeability rate and the diameter or buried depth of vertical pipe, where the power function indexes were 2.01 and -0.64, respectively. The well-established estimation formula of stable infiltration rate was also utilized to determine the drip discharge matching with the structural parameters of the vertical pipe, when there was no ponding in the vertical pipe. Subsequently, the infiltration test was conducted for the vertical-pipe drip irrigation. A field test was also carried out to observe the movement of wetting front in aeolian sandy soil under the different dripper discharge, buried depth, and diameter of vertical pipe. A power function was used to process the observed data. 7 treatments and 2 control tests were included in the field test. The dripper discharge was designed with the different levels of 0.9, 1.2, and 1.5 L/h, where the diameters of the vertical pipe were 10.6, 12.6, and 14.2 cm, and the buried depths of the vertical pipe were 15, 20, and 25 cm. The results showed that there was a significant effect of dripper discharge on the migration distance of the wetting front in the vertical downward. The migration distance of the wetting front was much greater in the vertical downward, whereas, slightly increased in the horizontal and vertical upward, as the dripper discharge became larger. Additionally, the migration distance of the wetting front in three directions decreased with the increase in the diameter of the vertical pipe. The migration distance of the wetting front in vertical upward and downward decreased, but the horizontal migration distance changed little, as the depth of the vertical pipe increased. The time of irrigation water was determined to reach the bottom hole of the vertical pipe, according to the water balance equation. A prediction model of the wetting body was established for the vertical-pipe drip irrigation, including the emitter discharge, diameter, and buried depth of the vertical pipe, as well as the irrigation time. The model was also verified by the 8 and the 9 schemes of the irrigation test. The average absolute error of the model was between 0.28 cm and 1.07 cm, while the root mean square error was between 0.19 cm and 1.68 cm, and the Nash efficiency coefficient was greater than 0.91. The finding can offer the accurate prediction of steady infiltration rate and wetting body in the optimal design of vertical-pipe drip irrigation system, thereby creating a relatively suitable environment for sand-fixing plant seedlings.

       

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