岩石CT密度损伤增量图像“阴阳环”现象的形成机制及其配准校正

通过对岩石试样在加载前后测得的CT数作差值运算,可获得岩石试样在不同应力阶段的CT密度损伤增量。在岩石CT密度损伤增量灰度图像中,试样边界被分成两半,其中一半为黑色,另一半为白色,这一现象称之为“阴阳环”现象。为揭示这一现象的形成机制,对岩石试样某一扫描断面在4个不同应力阶段CT图像的CT数分布进行对比研究。分析结果表明,加载阶段的CT图像相对初始CT图像发生错位。为查清图像错位与“阴阳环”形成之间的关系,建立“阴阳环”生成模型,同时揭示图像错位产生“阴阳环”现象的物理机制。在此基础上,对加载阶段的CT图像进行配准校正,消除密度损伤增量的计算误差。

FORMULATION MECHANISM OF HALF-WHITE BLACK CIRCLE IMAGES OF ROCK DENSITY DAMAGE INCREMENT WITH CT AND ITS REGISTRATION AND CORRECTION

Rock density damage increment with CT can be obtained by subtracting CT number of the undisturbed rock samples from that of the loaded rock samples.However,the special phenomenon may come into being when density damage increment data are translated into grey images.In such CT images,the circular contour line of rock samples is divided into two half circles.The half circle is white,and the other one is black.Such contour line of rock samples is called half-white black circle in this paper.In order to discover the information mechanism of the phenomenon,a group of CT test data,which are from the same scanning section of a sandstone sample at the four different stress steps,are used to analyze the CT number distribution.The analytical results show that there is the small offset between CT images,which is the reason that the half-white black circle phenomenon can be found in density damage increment images.After the small offset is corrected by registration processing,this phenomenon disappears.