包气带增厚条件下水分运移机理研究

Currently, various problems are required to be solved, such as the variation mechanism of groundwater recharge process and deep water migration law, and the change situation of water movement under the condition of unsaturated zone thickness increase. In order to solve the aforementioned problems, the in-suit test of water movement in unsaturated zone thickness increase, the comprehensive tracing method of the whole profile, the numerical simulation of water-air two phase flow, laboratory simulation, and hydraulic parameter test are employed to analyze the response mechanism of deep groundwater migration on the top-interface input. More importantly, these methods also can establish the water-air two phase model of unsaturated zone, detecting the water movement process, and revealing the evolution mechanism of water movement dynamic under the condition of unsaturated zone thickness increase and the process of groundwater nonlinear recharge, and therefore recharge rate of groundwater can be quantitatively characterized. It is concluded that this research play a significant effect on quantification analyze of the precipitation and irrigation infiltration mechanism, the conversation relationship of suspended water and groundwater. More importantly, it could help to better understanding the recharge process of groundwater and science deciding the groundwater infiltration replenishment. Therefore, this work is essential to achieve the sustainable utilization assessment of groundwater in the coming years.

包气带增厚条件下水分运移会发生什么变化，深部水分运移规律与地下水补给过程变异机制等问题已经广受关注，但悬而未解。本项研究拟通过典型包气带增厚区水分运移原位试验、全剖面同位素综合示踪、水-气二相流数值模拟、室内模拟及参数实验等方法开展包气带增厚条件下水分运移规律及变化特征研究，重点分析深部水分运移对上界面输入的响应机制，建立非饱和带水-气二相流模型，识别水分运移过程，揭示包气带增厚条件下水分运移动力学演变机制和地下水非线性补给过程，定量确定地下水入渗补给量。 研究包气带增厚条件下水分运移规律及变化机制，对定量分析降水和灌溉的入渗机理，深入探讨包气带水和地下水的相互转化关系，深入认识地下水的补给过程，科学确定地下水入渗补给量都具有重要意义，对地下水资源评价具有重要指导作用。

包气带增厚条件下水分运移会发生什么变化，深部水分运移规律与地下水补给过程变异机制等问题已经广受关注，但悬而未解。本项研究通过典型包气带增厚区水分运移原位试验、全剖面综合示踪、水-气二相流试验，深厚包气带水分运移数值模拟等方法开展了包气带增厚条件下水分运移规律及变化特征研究，识别了水分运移过程，定量确定了降水对地下水入渗补给量。取得的研究结果:. 研究区包气带厚度为45.0米，降水对地下水的补给周期为65.0-68.4年，降水在包气带的平均运移速率为0.65-0.70m/a，研究区降水对地下水多年平均补给强度为103.1-117.0mm/a，占多年平均降水量的19.3-21.8%。. 深厚包气带地区水分入渗速率不仅与包气带岩性，而且与地层埋深密切相关，12-15米是包气带水分运移变化的临界点，12-15米以浅，水分入渗速率变化大且主要受包气带岩性影响，砂层入渗速率为1.0-1.2m/a，粘性土层入渗速率为0.3-0.35m/a；12-15米以深，砂层中入渗速率为0.6-0.9 mm/a，粘土层中入渗速率为0.35-0.4 m/a，岩性对入渗速率影响显著减小，包气带深部受长系列多期降水叠加驱动影响，长期处于缓慢入渗状态，且平均入渗速率基本稳定。. 包气带深部水分运移是长系列多期降水叠加驱动的结果，深部主要发生水分积累-入渗往复循环过程，但水分积累-入渗周期很长。. 包气带岩性对水气二相流有着重要影响，水气二相流易发生在粉质粘土、粘土等细粒层。不同深度细粒层水分运移的滞后时间和滞留时间均有较明显差异，深部细粒地层是水气二相流发生的重点层位，细颗粒层的水气二相流过程是控制水分运移入渗的关键因素，当水-气相驱在细颗粒层中发生周期越长，水分越难于入渗，垂向渗透作用越弱。. 本项成果对深厚包气带地区水文过程研究和水资源科学评价都具有重要的借鉴意义。