基于颗粒模型的风积砂层降雨入渗深度计算及验证  

Calculation and validation of wetting depth of infiltration in aeolian sand in arid areas based on particle model

作　　者：黄德文[1] 陈建生[1,2] 詹泸成[1] 

机构地区：[1]河海大学土木与交通学院,南京210098 [2]河海大学地球科学与工程学院,南京210098

出　　处：《农业工程学报》2016年第14期129-134,共6页Transactions of the Chinese Society of Agricultural Engineering

基　　金：国家重点基础研究发展计划项目(973计划)(2012CB417005);江苏省高校研究生科研创新计划项目(CXZZ12-0231)

摘　　要：为了研究沙漠干旱区降雨对砂层非饱和带水分的贡献,该文对风积砂层水分入渗过程中的水分存在形式和运移机理进行了理论和力学分析。通过以触点水为主要储水单元的立方布局颗粒模型推导出水分入渗过程中湿润深度的解析表达式,并进行验证。物理和力学分析表明,砂颗粒表面很难形成较厚的薄膜水,砂层非饱和带水分大部分以触点水的形式存在。模型计算结果表明,水分入渗的湿润深度与入渗水量和触点水湿润角有关。模型验证表明,水分入渗湿润深度的解析表达式在风积砂层入渗深度计算中具有一定的适用性,但触点水湿润角与砂颗粒粒径的函数关系还有待进一步研究当设定触点水湿润角为π/4时,比例常数为11.5。该研究可为干旱区农业规划提供依据。In Badain Jaran Desert, an extremely arid region with annual precipitation of 100 mm and annual evaporation of 3 000 mm, the sand underneath a dry surface layer of about 20 cm is relatively wet. Even at the top of the giant dunes, which is about 300 m high, the moisture content at the depth of 2 m is more than 3% in a volumetric fraction. The provenance of soil water in the wet sand layer has always been in dispute over decades. In order to give a better understanding of the contribution of local rainfall to the soil water in unsaturated sand layers, the theoretical analysis and model calculation was conducted. The physical and mechanical mechanisms of moisture movement in the process of water infiltration were analyzed, and the states of moisture in unsaturated sand layers were taken into consideration. Focusing on the microscopic physical model, by the assumptions of spherical particles, the descriptions for the formation mechanism on pendular water and water retention attributed by pendular water in particle materials were presented. And the analytical expressions for rainfall infiltration depth were derived based on the cubic particle model, in which the pendular water was the main water storage unit. To verify the applicability of the derived expressions in sandy soil, the field artificial water infiltration experiment was conducted in sandy soil of the Badain Jaran Desert. Based on the physical and mechanical analysis, sandy particle surface was difficult to hold the relatively thicker film water because of the relatively large particle size and the small surface charge density. The most part of liquid water in unsaturated sand soil was located between particles in the form of pendular water. The derived expressions of wetting depth of infiltration indicated that the wetting depth depended on the amount of precipitation and the wetting angle of pendular water. The initial moisture content of sand soil also had an effect on the depth of infiltration. Based on the balance between gravity and surface tension i

关 键 词：入渗 土壤水 降雨 干旱区 风积砂 触点水 湿润深度 

分 类 号：S152.7[农业科学—土壤学]