中文摘要：

模拟非饱和黄土地表蒸发，对不同初始含水量和干密度土体进行了室内外蒸发试验，探讨了不同初始含水量和干密度下均质土样蒸发过程中水分场变化规律，对比分析了室内外试验结果，并解释了室内外试验结果的差异性。结果表明：室内外试验得到的蒸发强度和潜在蒸发强度差别较大，但蒸发系数差别较小，蒸发系数主要受含水量的影响，干密度对其影响不大；不同初始含水量下均质土体的蒸发系数随时间呈指数型减小。进而揭示出，任一时段蒸发系数主要与地表含水量、浅层土含水量梯度有关。

英文摘要：

In order to explore the surface evaporation mechanism of the unsaturated loess, a series of indoor and outdoor evaporating tests were carried out on soil samples with various initial moisture and dry densities. This paper explores the moisture migration rule of the soil samples in the process of the evaporation, analyzes the results of in- door and outdoor experiments and discusses the diversity of those experimenting results. It is concluded that there was a considerable difference in the evaporation intensity and potential evaporation between indoor and outdoor ex- periments but a small difference in the evaporation coefficient, which was closely related to the water content and was slightly affected by the dry density. The evaporation coefficient of the uniform soil with different initial moisture contents reduced exponentially over time. It further revealed that the soil evaporation coefficient at any time was mainly related to the water eontent of land surface and the moisture content gradient of the shallow soil. Based on the tested data, a formula which contains the water content of the soll surface and the moisture content gradient of the shallow soil is built up to determine the soil evaporation coefficient.