基于X-CT扫描成像技术的级配碎石冻结状态细观研究

Mesoscopic Study on Frozen State of Graded Crushed Stone Based on X-Ray CT Scanning Technology

以高速铁路基床表层级配碎石为研究对象,基于X-CT扫描成像技术进行级配碎石冻结状态细观研究。利用X-CT扫描技术结合图像处理技术重构冻结状态下的三维级配碎石试样模型。通过断层扫描图像的灰度识别技术,辨识出级配碎石中不同组分的灰度范围,进而获取级配碎石颗粒、冰晶和孔隙的分布特征。不同饱水度和细颗粒含量级配碎石冻结状态的X-CT扫描分析结果表明:冰晶主要聚集在试样的孔隙和粗、细颗粒交界处;冰晶含量随饱水度增加而增加,孔隙率随细颗粒含量的增加而减少;级配碎石冻胀有别于传统细粒土冻胀,主要在细颗粒聚集区发生水分微迁移,推动粗颗粒旋转、错动,使其偏离原来的位置,引发冻胀。

Taking the graded crushed stone on the subgrade bed surface of high speed railway as the research object,the mesoscopic study on the frozen state was carried out based on X-ray CT scanning technology.The three-dimensional graded crushed stone sample model in frozen state was reconstructed by using X-ray CT scanning technology combined with image processing technology.By means of the grayscale recognition technology of tomography images,the grayscale range of different components in graded crushed stone was identified,and the distribution characteristics of graded crushed stone particles,ice crystals and pores were obtained.The results of X-ray CT scanning a nalysis for the frozen state of graded crushed stone with different degrees of saturation and fine grain contents show thatice crystals are mainly concentrated in the pores as well as at the junctions of coarse and fine grains of the samples.The content of ice crystal increases with the increase of saturation degree and the porosity decreases with the increase of fine grain content.The frost heave of graded crushed stone is different from that of traditional fine grained soil.Micro-migration occurs mainly in fine grain accumulation area,which drives the coarse particles to rotate and stagger,deviate from the original position and result in frost heave.