包气带中温度变化对水分分布影响的实验研究

A testing study on the effect of the change of temperature on the occurrence of water content in unsaturated zone

笔者在高180cm、宽50cm的砂槽中,做了温度对水分运移影响的模拟试验。试验结果表明,在包气带一定深度以下,孔隙相对封闭,孔隙内液态水与气态水处于动态平衡,相对湿度接近或达到饱和状态。在此条件下,砂柱内温度场的任何微小变化都会导致孔隙系统内的水分发生蒸发或凝结。当包气带内温度场发生变化时,气态水在温度梯度作用下,向最低温度界面运移,蒸发或是凝结取决于最低温度界面的性质。在不发生聚集的开放性界面上出现蒸散,消耗包气带内水分。在聚集性封闭界面上则出现凝结,使包气带内水分增加。在温度场控制下,包气带中气态水凝结或蒸发是水分运移的另一重要形式,它在一定程度上决定着水分的分布状态,尤其在温差巨大的地区,这种作用显得十分重要。

Modeling tests showing the effect of temperature on water transport were conducted with a sand column of 180 cm high, 50 cm long and 50 cm wide. The results indicated that under a certain depth in the unsaturated zone the pores were relatively closed, liquid water and gaseous water in the pores were in a dynamic equilibrium state, and the relative humidity approached or reached the saturated state. Under the above conditions, any minute change in temperature in the sand column may lead to evaporation or condensation of water content in the porous system. When the temperature in the unsaturated zone changed, the gaseous water transported towards in minimum temperature interface owing to temperature gradient, and evaporation or condensation occurred, depending on the nature of the minimum temperature interface. Evaporation occurred on the open interface where accumulation of water content did not happen, and the water content in the unsaturated reduced. On the other hand, condensation occurred on the accumulative and closed interface, and the water content in the unsaturated zone increased. Under the influence of temperature, condensation or evaporation of gaseous water is another important from of water transport in the unsaturated zone. It determines the occurrence of water content to some extent, especially in regions where differences in temperature are relatively large.