黑土冻融过程中水分垂直迁移模拟研究

Simulation of Water Vertical Migration in Black Soil During Freezing-thawing Process

为明确土壤冻融过程中水分垂直迁移与其主要影响因素间的定量关系,以我国东北典型黑土为研究对象,通过单向冻融试验,进行了不同初始含水率、降温幅度和地下水位条件下土壤冻结过程中水分垂直迁移试验,定量分析了主要影响因素对黑土冻融过程中水分垂直迁移的影响规律。结果表明:(1)试样中温度变化先快后慢,最终试样内部温度随深度呈现稳定的温度梯度分布;(2)初始含水率对土壤的冻结影响较为明显,初始含水率越高,冻结经历时间越长,冻结过程中消耗的潜热量越大,冻结锋面形成越晚;(3)不同降温幅度使得土壤温度梯度差距较大,15℃温差变温时垂直方向水分迁移量最大,土壤最快进入冻结稳定期,并在冻结16 h时,20 cm土层附近含水率达到冻结期峰值;(4)地下水位越高,温差越小,冻结锋面向下迁移速率越慢,各层水分均明显增加,并且在中上层聚集。

In order to clarify the quantitative relationship between the moisture vertical migration and the main influencing factors during soil freezing-thawing process,a unidirectional freezing-thawing simulation test was carried out using typical black soil in Northeast China,under the conditions of different initial moisture contents,temperature drop ranges,and groundwater levels.The results showed that:(1)The temperature changes in the samples were fast first and then slow,and the internal temperature of the samples showed a stable temperature gradient distribution with the variations of the depths.(2)The influence of initial moisture content on soil freezing was obvious.The higher the initial moisture content of soil was,the longer the duration of freezing process was,and the larger the latent heat consumed in the freezing process was,and the later the formation time of freezing front was.(3)Various temperature drop ranges caused the obvious difference of soil temperature gradients.The migration of water in the vertical direction was the largest with the temperature changes at 15℃,the soil entered the freezing stable stage at fastest speed,and the moisture content near the 20 cm soil layer reached the peak value after 16 hours.(4)The higher the groundwater level was,the smaller the temperature difference was,the slower the downward migration rate of the freezing front was.The water content in each layer increased significantly,and accumulated in the upper and middle layers.