滴灌农田暗管排水排盐条件下的水盐运移规律及暗管工程设计参数优化研究

After drainage systems was wasted in farmland with drip irrigation, farmland salinization cannot be eradicated even deteriorated. Arrangement of subsurface pipe is proposed for farmland with drip irrigation, which discharge salt and discharge winter in the final stage of autum and preliminary stage of winter. Soil salinity conditions, hydro-geological conditions, soil physical properties and hydrodynamic parameters of soil in farmland with drip irrigation and covered conduits ,which were analyzed for effect on profile two-dimensional migration, distribution characteristics, the size of content, so that migration dynamics of soil water and salt is proven. Coupling variable soil water and salt, so that movement modle of water and salt in soil under condition of discharge by covered conduits in the drip irrigation farmland is established. Based on the model, combined with field experiments and field engineering, the modle is fitted with migration dynamics of soil moisture and salt in farmland with drip irrigation and covered conduits in order to prove the law of migration dynamics of soil moisture and salt in farmland .Designing different drainage engineering specifications in farmland with drip irrigation, and monitoring effect of underground water tables falling and desalination after subsurface drainage were used in the farmland with drip irrigation, the law which water and salt in the soil dynamic response to covered conduits in the farmland with drip irrigation is researched. Due to effect of underground water tables falling, desalination, difficulty of the construction, economic rationality，engineering design parameters were optimized in farmland with drip irrigation, then the optimal combination of spacing and depth portfolio were determined. A theoretical basis is provided for farmland planning and design which with drip irrigation and subsurface pipe by research.

针对膜下滴灌农田废弃排水系统后，农田盐渍化无法根除甚至加重的问题，提出在滴灌农田布置暗管，利用秋末冬初压盐水进行排盐、夏季排除地下水。分析滴灌农田暗管排水条件下，土壤含盐状况、水文地质条件、土壤物理特性及土壤水动力学参数对土壤剖面水盐三维运移、分布特征的影响，探明土壤水盐迁移动力学过程；以土壤含水量、含盐量为耦合变量，构建滴灌农田暗管排水条件下水盐运移模型；基于构建模型，结合田间试验及已建工程，对滴灌农田土壤水分、盐分运移进行拟合，探明滴灌农田暗管排水条件下水盐运移规律；设计不同的滴灌农田暗管排水工程规格布局，监测滴灌农田使用暗管排水后降水、脱盐效果，研究滴灌农田暗管排水条件下水壤盐动态对滴灌农田暗管排水的响应；根据暗管达到不同降水、排盐效率、施工难易、经济合理性等指标优化滴灌农田暗管排水工程设计参数，优化间距和埋深组合。研究结论可为滴灌农田暗管排水规划设计提供理论依据。

针对膜下滴灌农田废弃排水系统后，农田盐渍化无法根除甚至加重的问题，提出在滴灌农田布置暗管，利用秋末冬初压盐水进行排盐、夏季排除地下水。分析滴灌农田暗管排水条件下，水文地质条件、土壤物理特性及土壤水动力学参数对土壤剖面水盐三维运移、分布特征的影响。通过室内实验和数值模拟，分析饱和条件下的暗管排水与非饱和条件下暗管排水条件及排水特征差异，排水过程及排水效率的差异。提出：非饱和条件下，不能再用土壤饱和导水率作为评价排水性能的依据，而应该考虑能使暗管周围形成饱和水的要素作为评价指标；传统用于饱和条件下的暗管全外包滤料的结构形式就不再适合于非饱和条件下的暗管排水的观点。并设计出一种改善农田暗管排水效率的暗管排水系统模式及暗管滤层结构形式。通过在滴灌农田规划布设不同排水工程规格，监测滴灌农田使用暗管排水后降水、脱盐效果，发现室内实验与田间实验的不一致性，认为农田层状结构和大孔隙结构是造成室内试验和田间实验存在结果差异的主要原因。而以上研究内容都是现有农田排水工程设计规范中所急需补充的内容，研究结论可为滴灌农田暗管排水规划设计提供依据