恒定大气条件下砂土蒸发机制的模型试验研究

MODEL TEST STUDY OF EVAPORATION MECHANISM OF SAND UNDER CONSTANT ATMOSPHERIC CONDITION

采用大尺寸模型试验对法国枫丹白露砂土的蒸发机制进行研究。利用模型箱进行各种大气条件下砂土上覆水层蒸发试验,验证模型箱的工作性能和蒸发速率的计算方法;而后进行恒定大气条件下的大体积砂土(无上覆水层)水分蒸发试验,研究蒸发过程中大气参数和土体参数的变化,并根据试验结果对砂土蒸发机制和实际蒸发速率进行分析。研究结果表明:模型箱工作性能良好,所采用的蒸发速率计算方法合适;土体温度受土体蒸发过程的影响;土–大气交界面存在2个较大的温度梯度;空气的相对湿度随着蒸发的进行逐渐降低;土体蒸发对土体含水量的影响与蒸发时间和土体阻抗有关;土体浅层基质吸力梯度随蒸发的进行逐渐增大。

The evaporation mechanism of Fontainebleau sand using a large-scale model chamber is studied. First, the evaporation test on a layer of water above sand surface is performed under various atmospheric conditions, validating the performance of the chamber and the calculation method of actual evaporation rate by comparing the calculated and measured cumulative evaporations. Second,the evaporation test on sand without water layer is conducted under constant atmospheric condition. Both the evolutions of atmospheric parameters and the response of soil are recorded. The evaporation mechanism of sand and its actual evaporation rate are analyzed using the recorded data. The results show that the chamber exhibits a good performance and the calculation method of actual evaporation rate is relevant. Moreover,evaporation process affects soil temperature. Two large temperature gradients are identified at soil-air interface. The relative humidity of air decreases along with the evaporation process. The effect of evaporation process on soil volumetric water content is related to evaporation duration and soil resistance. The matric suction gradients of soil at surface zone increase during evaporation.