冻土正融过程CT扫描试验及图像分析

为了探索冻土正融过程中CT图像灰度值随时间变化的特点。将-27 ℃的冻土试样放置在20 ℃的室温环境中依靠与空气自然对流加热融化，同时连续地进行CT扫描，得到各时刻的CT灰度图像，并记录温度-时间变化曲线。通过对试样各个时刻CT图像平均灰度值的统计，得到CT图像的时间-灰度变化曲线，并与试样的时间-温度变化曲线进行对比。结果表明：在冻土温度上升和融化过程中灰度均值随时间呈明显上升趋势。在冻土完全融化后，虽然温度继续上升，但灰度均值基本不发生变化。因此，在冻土融化完成时刻，在时间-灰度图像上出现一个明显的折点，该折点可以视为冻土融化完成的标志。

CT scanning and images analysis during frozen soil thawing

The purpose of the experiment was to explore the feature on grayscale of CT images during frozen soil thawing.Siltyclay sample was taken into isothermal air (20 ℃)to melt by natural convection after being frozen at -27 ℃ ，and the CT images were obtained by X ray scan，at the same time，its temperature time history was recorded.The curve of grayscale time was acquired by counted CT images at each moment，and compared with its temperature time history.The results show that the average grayscale increases obviously with temperature rising and thawing in frozen soil.However，after sample thaws completely，the average grayscale is not practically changing even temperature still rising.A break point is obviously observed in the graph of grayscale time at the moment of phase transition finished，which is considered as a symbol of frozen soil melting complete.