低温水入渗条件下土壤水分温度动态变化

自制土槽试验装置,室内模拟低温水在河岸带土壤中非饱和入渗的过程。以填装中细砂为研究对象,进行了3种不同水头下的低温水入渗试验,对低温水在土壤中的入渗过程和水分、温度时空动态作了连续监测,分析了水头对入渗参数、水分场与温度场的影响规律。试验结果表明:在相同时间内,入渗水头越高,湿润锋垂直(水平)运移距离越大,垂直湿润锋的运移速度随入渗时间的增加有逐渐减少的趋势,最后逐渐趋于稳定;水头5 cm作用时入渗率波动较大,稳定时间大于水头25 cm和45 cm作用时土壤达到稳定入渗率所需的时间;入渗水头越高,平均温度下降越快,温度场也更快地达到相对稳态,水头25 cm在低温水入渗420 min后基本上达到稳态,水头45 cm在240 min后基本达到稳态。

Dynamic variation of soil moisture and temperature under infiltration of low-temperature water

An experimental study was conducted in an indoor soil tank, to examine low-temperature infiltration and movement through unsaturated soil in topsoil layer of riparian zone. Low-temperature water infiltration tests were carried out at three different heads in the filling fine sand. Infiltration process, moisture and temperature fields were continuously monitored and analyzed to study the impacts of the water head, the infiltration parameters, and moisture and temperature fields. Results showed that the higher the infiltration head, the greater is the vertical (horizontal) migration distance of the wetting front. The migration velocity of the vertical wetting front also gradually decreased with increasing infiltration time, and becoming more and more stability at the end. Infiltration rater had the larger fluctuations at the head of 5 cm and the settling time is greater than the head of 25 cm and 45 cm. The higher the infiltration head, the faster is the decreasing rate of average temperature before the temperature fields could go into a relatively steady status. At the head of 25 cm, infiltration of the low temperature water basically reached steady status after 420 min and the head of 45 cm is after 240 min.