冻融环境中饱和岩石的热量传递与温度平衡规律

 冻融环境中温度是岩石性态变化的关键影响指标之一，而冻融试验中岩石的热量传递和温度变化规律国内和国际都未形成统一认识。为探究岩石在冻融环境中的热量传递和温度变化规律，利用室内试验和数值计算方法分别研究冻结和融化过程中试样温度平衡的过程和时程规律。利用3种岩石进行饱和态的冻融循环试验，试样中心温度监测表明，冻结和融化过程的试样温度均存在显著的3段式变化特征，其中相变过程是一个较为特殊和重要的阶段，相变温度均在0 ℃～－1 ℃范围。随着试验温度区间增大，冻结和融化各阶段时长显现出不同规律，冻结过程总时间逐渐降低，而融化过程总时间先降低后升高。基于第3类热传导边界条件，利用Comsol Multiphysics有限元数值计算平台，分析考虑相变阶段的冻结和融化过程，数值计算结果与试验结果吻合较好。数值计算结果显示，试样不同位置的冻结与融化特征主要体现在相变阶段差异，而试样孔隙率对该阶段的影响最大，剩余温度势造成对称温度区间和非对称温度区间的冻结、融化特征的显著差异。

Thermal transfer and heat balance of saturated rock under freezing-thawing environment

In the freezing-thawing environment，temperature is one of the key factors influencing the physical and mechanical characteristics of rock. However，the thermal transfer and temperature change in rock in the freezing-thawing test have not been fully understood. The experimental and numerical methods were therefore applied to analyse the process of heat balance. Three kinds of rocks were studied in the freezing and thawing tests with the temperature being monitored. The process of central temperature change contains in three stages such as the precooling stage，the phase transition stage of moisture and the cryogenic stage during freezing，and the process during thawing includes the preheating stage，the phase transition stage of moisture and the deep heating stage. The phase transition stage is special and significant in the freezing and thawing test. The temperature of phase transition is between 0 ℃ and －1 ℃ for all the specimens. As the temperature range increases，the durations of each stage in the freezing and thawing processes are different. The total duration decreases gradually in the freezing process，but decreases first and then increases in the thawing process. The processes of freezing and thawing for the saturated rock were analyzed with the software of Comsol Multiphysics considering the phase transition of moisture. The results of numerical simulation match well with the test results. According to the numerical simulation results，the characteristic differences of the freezing and thawing process are mainly in the phase transition stage and the porosity of rock influences the stage greatly. The residual of heat potential results in the differences between the symmetrical and unsymmetrical temperature range in the freezing and thawing process.