岩土材料中冰分布状态的冷冻电镜表征方法

Characterization of Ice Distribution in Geotechnical Materials Based on Cryo-electron Microscopy

为从微观角度定量描述冰在岩土材料中的分布特征,基于冷冻电镜技术提出了一种微观尺度的实验表征方法。针对不同冰饱和度人造岩芯样品的二次电子图像和能谱分析图,通过元素含量分布、升华前后图像对比确认了冰在岩土材料中的分布状态。随着冰饱和度的增加,骨架孔隙被冰填充、骨架颗粒表面被冰包裹区域增大,样品断面更密实平整,岩土骨架的堆积结构特征变弱。在背散射电子图像中,冰的图像比岩土骨架亮度低、灰度高,基于此构建了冰饱和度的数字图像计算方法。该方法计算的升华前冰饱和度与样品预制冰饱和度偏差小于5%,验证了其可靠性。

Quantitatively describing the distribution characteristics of ice in geotechnical materials from a microscopic perspective is crucial.Based on the technique of cryo-electron microscopy(Cryo-EM),an experimental characterization method of the distribution of ice in porous geotechnical materials is proposed.For artificial core samples with different ice saturations,the distribution of ice in porous geotechnical materials is confirmed by elemental content distribution and comparison of images before and after sublimation based on the secondary electron(SE)images and energy spectrum analysis maps of the samples at different magnifications.With the increase of ice saturation,the pore space of the skeleton is filled by ice,the area of the skeleton particle surface wrapped by ice increases,the sample section is denser and flatter,and the stacking structural characteristics of the geotechnical skeleton become weaker.In the backscattered electron(BSE)image,the image of ice is less bright than that of the geotechnical skeleton,based on which a digital image calculation method for the ice saturation of the sample is developed.The deviation of the ice saturation calculated by this method before sublimation from the ice saturation of the predesigned sample is less than 5%,and the results are accurate and reliable.