非饱和土壤内部水-气界面特性的微CT分析

MICRO-CT ANALYSIS OF PORE-SCALE WATER-AIR INTERFACIAL BEHAVIOR IN UNSATURATED SOIL

以不同粒径玻璃微珠为对象,通过高分辨率Micro-CT测量获得非饱和土壤内部水-气界面的分布状态特征,并采用欧拉数(Eu)表征土壤内部孔隙的连通特性。结果表明,Eu随饱和度S变化可分为3个阶段,其中当S<25%时,Eu随饱和度线性降低;当25%<S<35%时,Eu随饱和度缓慢降低,直至减小至零;当S>35%时,Eu呈现负值,且变化非常微弱。土壤内部的水-气接触面积随饱和度的增加呈现快速上升而后逐渐下降的整体变化趋势。最后,以热导率为例,量化水-气界面状态变化对不同温度下土壤宏观热物性的影响,并分析土壤内部水-气扩散与流动机制。

Aiming at micro glass beads with different diameters, the pore-scale water-air interfacial behavior in unsaturated soil was observed and measured by using a micro-CT scanner with high resolutions, and the Euler number was used to analyze the connectivity of micro pores in soil. The results show that the variations of the Euler number with saturation S can be divided into three major stages： when S〈25%, the Euler number with S decrease linearly; when 25% 〈S〈 35%, the Euler number with S decrease very slowly until zero; when S〉35%, the Euler number is negative and varies very weakly. As the saturation increases, the water-air interfacial area increase quickly and then decrease gradually. Finally, taking thermal conductivity as an example, the effect of the changes of the water-air interfacial status on the macroscopic thermophysical properties of soil under different temperatures is quantitatively analyzed, and water- air diffusion and flow mechanism in soil is revealed.