【作者】 李娟；

【导师】 马孝义；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2007， 硕士

【摘要】 研究地下滴灌的点源入渗规律,对提高地下滴灌系统设计、运行管理水平具有重要的理论意义。本文以土壤水分动力学理论为基础,研究多种土壤在不同容重条件下重力式地下滴灌的入渗规律,构建了重力式地下滴灌的土壤水分运动模型。将试验验证与数值模拟相结合,得出如下结论:1)对试验所用中壤土和砂壤土不同容重下的土壤水分特征曲线和扩散率进行了测定,并对参数进行了拟合,获得了VG模型的有关参数值,表明VG模型可以很好表征试验土壤水分特征曲线和扩散率随土壤含水量的变化特征。2)建立了柱坐标系下重力式地下滴灌三维土壤水分运动模型,利用有限元法求解;通过多组重力式地下滴灌土槽试验,测定其土壤水分入渗动态含水量变化过程,获得土壤水分运动过程及其分布的试验数据。用所建模型对地下滴灌土壤湿润体水分分布进行模拟,将模拟值与实测值进行了对比分析,结果表明:模拟值与实测值误差小,所建模型具有较强适用性,可用于重力式地下滴灌点源入渗和湿润体特征的分析。3)利用建立的模型,模拟多种土壤不同灌水技术要素组合下湿润体土壤水分分布和滴孔出流量变化的规律,得出在相同灌水量下,管道埋深对湿润体影响较大;供水压力与滴孔孔径对湿润体影响微弱,因此地下滴灌管道设计时可不考虑其影响,只需根据田块长度和渗水管损失确定重力式地下滴灌的孔径和供水压力;在地下滴灌工程中允许较小的供水压力供水,这样可以减小供水池高度以见少工程投资;供水压力与滴孔孔径对滴孔出流量影响较大,而其它因素对其影响微弱,这些结果可为重力式地下滴灌系统的设计与运行提供参考。4)根据已有黄土高原几种典型土壤的水分特征曲线和扩散率数据,对其土壤水分运动参数进行拟合,获得了VG模型的相关参数值,并模拟了不同孔径、不同供水压力条件下重力式地下滴灌点源入渗特征,这些结果对黄土高原推广应用重力式地下滴灌有重要的参考价值。更多还原

【Abstract】 This paper had deeply studied the soil water movement regulation of the subsurface drip irrigation. It had important academic significance and utilizing value to improve the design precision of Gravity Subsurface Drip Irrigation, extending scientific and technological application of subsurface drip irrigation and guiding the run of the irrigation system. simulated water movement regulation of SDI. The results were shown as follows:1) The characteristic curve of soil moisture detention and soil moisture diffusivity of loam and sandy loam of two kinds of density was measured, and the parameters were also simulated. We also abtaind the VG model parameter, This showed VG model can be used very well to express the soil water retention and diffuivity and soil water content curve.2) We established a three-dimensional axisymmetric model of soil water movement of GSDI and deduced the solving of finite element, The soil box experiment of gravity type SDI, which was designed with orthogonal included six kinds, measured the dynamic moisture content changes of soil infiltrated water under SDI conditions. We also got the water movement procession and distribution experiment data in soil and simulated the changes of moisture content movement distribution and fluctuation in discharge under SDI using established model in this study, compared that simulated values with measured values, which has analyzed, the results showed that the simulated volumes had little difference from experiment results.The established model can be used to simulate the water soil movement under drip irrigation.3) Using the established model, to simulate the effect of irrigation technical elements, which concluded different apertures, different water pressure, different buried depth trickle and different soil density etc. Water pressure and apertures had smaller effects on soil water movement with the same irrigation quantity, so they can be neglected when designing the gravity surface drip irrigation pipes. However, Water pressure and apertures have an evitable influence on trickle discharge rate compared to other factors. We can design water pressure and apertures of the drip irrigation pipes only according to field length and water-head losses of seepage pipes. Smaller water pressure can be also used to lower invest to the project,which could offer definite academic basis for the design and operation of SDI system.The water pressure and apertures had significant effects on the trickle discharge,which could offer definite academic basis for the design and operation of SDI system.4) Parameters of the soil water characteristic curve and diffusivity were simulated according to available date of several soil textures in Loess Plateau, by which the VG model parameters were obtained and soil water movement effect had been simulated in different apertures and water pressures. Which provides a reference for the extend application of gravity subsurface drip irrigation in Loess Plateau.更多还原