黄土高原旱区浅层黄土水分场的数值分析

Numerical Simulation of Moisture Field in Shallow Loess of Loess Plateau During Continous Drought

[目的]研究黄土高原浅层土体水分场在春季连续干旱条件下的动态变化。[方法]通过非饱和黄土二维非稳态流有限元控制方程对黄土高原浅层土体水分场在不同气象条件下的动态变化进行数值计算。[结果]在连续干旱条件下水分场的计算结果与实测结果较为一致,受蒸发影响的土层最大厚度为1.8m,连续3个月的干旱使其平均含水率降低至7.9%,土壤蒸发强度随着含水率的减小而减小。强度较小且分散的降雨对于缓解连续干旱期黄土高原土壤干旱基本无效,大强度集中降雨只能在短时间内缓解土壤旱情。[结论]数值计算结果可为实际工程中植被类型的选择以及灌溉时间的把握所参考。

[Objective] To analyze the dynamic change characteristics of moisture field in shallow loess of Loess Plateau during the continuous drought. [Methods] The dynamic changes of moisture field in shallow loess were calculated numerically by the unsaturated loess unsteady flow 2 dimension finite element control equation under the three different meteorological conditions.[Results] The calculation results were consistent with the measured results during the continuous drought, the thickness of loess affected by the evaporation was 0~ 1.8 m. Three consecutive months of drought makes its average moisture content dropped to 7.9%, the evaporation intensity of the loess decreased with the decrease of moisture content. The scattered and low intensity rainfall for alleviating continuous drought is invalid basically. The concentrated and intensive rain- fall can alleviate soil drought only in a short period. [Conclusion] The results of numerical calculation can provide references for the choice of vegetation types and irrigation time.