重塑黏土单向冻结过程中水分迁移试验研究

利用室内水分迁移试验装置,通过改变土体初始含水率和温度梯度,进行土样单向冻结试验,研究含水率和温度梯度对土体中水分迁移和土样冻结过程的影响。结果表明:土样冻胀后在上部冻结区产生了不规则网状裂缝,裂缝最密集区域含有大量冰晶体,导致此处出现含水率峰值,峰值大小主要受初始含水率影响,但其出现位置主要由温度梯度决定; 上部冻结区增加的含水量来源于外界水分补充和未冻结区的水分迁移,下部未冻区的含水率较初始状态降低,其降低程度主要受初始含水率控制; 在整个冻结过程中,外界水分一直向土样内部迁移,水分迁移速度先增大再降低,温度梯度增大导致入流量和入流通量相应增加,初始含水率越大则入流量越小; 土样冻胀速率和冻结速率主要受温度梯度影响,整体趋势都是先增大到峰值,再逐渐降低并趋于稳定。

Experimental study on moisture migration in remolded clay during unilateral freezing

Moisture transfer in soil plays an important role on the subgrade soil frost heave, and the water content and temperature gradient are the main factors affecting soil moisture migration. Unilateral freezing test was carried out with the indoor moisture migration test apparatus, which can adjust the initial moisture content and the top temperature to explore the effects of moisture and temperature gradient on the soil moisture migration and soil freezing process. The results showed that, in the upper area of the frozen sample soil, irregular reticular cracks occurred. Inside the densest section of the cracks, a large number of ice crystals existed, making the water content peaks in the soil sample. The magnitude of the water content peak was mainly affected by the initial moisture content, while the location was mainly determined by the temperature gradient. The increased water content of the upper frozen zone came from the external water supplement and moisture migration from the unfrozen zone. Correspondingly, the moisture content of the lower unfrozen zone decreased, and the decrease was mainly affected by the initial moisture content. During the whole freezing process, the external water remained migrating into the soil, and the speed of water migration increased initially and then decreased. The increase in temperature gradient would increase both water intake and flux rate. The higher the initial moisture content, the smaller the water intake would be obtained. The frost heaving rate and the freezing rate were mainly affected by the temperature gradient. The overall trend initially increased to a peak, then gradually decreased and finally stabilized. Thus, a slight increase in initial water content in soil can reduce the amount of water migration in the freezing process, and the frost heave of soil can be decreased and delayed obviously by increasing the thickness of pavement structure so as to reduce the frost temperature gradient inside the subgrade soil.