使用图像分析方法研究单轴压缩条件下花岗岩中细观组分的定向性变化

Orientation of meso-components in granite under uniaxial compression using image analysis

使用图像分析方法,根据室内单轴压缩试验视频图像对花岗岩细观组分定向性的变化情况进行了分析。在对原始视频图像进行可读格式转换后,将可读视频图像转换成多帧静态图像,截取相同位置、相同大小的图像区域进行灰度化处理。对截取的每帧静态图像使用不同阈值识别花岗岩细观组分,得到不同时刻不同细观组分区域的分布情况。计算不同细观组分区域的长轴和短轴大小,根据各区域长短轴大小确定最小外接矩形,由长短轴交点与长轴中点定义长轴方向向量以计算全方向[0°,360°]内的长轴方向,进而计算不同细观组分区域的长轴走向,绘制不同时刻不同组分的长轴走向等值线图;计算不同时刻不同细观组分区域的面积以及概率熵,得到整个加载过程面积和概率熵的变化曲线。整个计算分析过程由自编程序自动实现。结果表明,在单轴压缩条件下花岗岩细观组分的定向性发生改变;不同细观组分的定向性增强区间相间分布、定向性减弱区间互不重叠,但某些区间为一种组分的定向性增强区间、另一种组分的定向性减弱区间;石英、长石、黑云母在加载过程中依次受力;不同细观组分在受力时面积变化出现明显异常;花岗岩中黑云母分布的有序性高于石英和长石;石英和长石在受力后区域分布变得有序,而黑云母在整个试验过程中的定向性无明显变化。研究成果对岩石变形破坏过程机理研究具有一定的参考价值。

The orientation of meso-components in granite was investigated using video images from the laboratory uniaxial compression tests. The video images were converted into static images after the pretreatment of the original ones. The images with the same position and size were clipped and gray-converted in each static image. The distributions of different meso-components at different times were obtained by using different thresholds to recognize each meso-component in granite. The minimum enclosing rectangles were identified by the major and minor axes. The tendencies of each meso-component investigated in the whole region of [ 0° 360° ] were obtained based on the positions of the midpoint and the intersections of the major with minor axis. The major axis trend and area and the probabilistic entropy of different meso-eomponents were further computed. The contour maps of the major axis trend and the variation curves of area and probabilistic entropy were thereafter visually drawn. The whole process of calculation was automatically generated using the programs compiled by the authors. The results show that the orientation of meso-components in granite under the uniaxial compression may be presented using image analysis; the enhancement or decrease intervals of orientation of different meso-components were not overlapped separately; the quartz, feldspar, and biotite were successively loaded during the compressions; the areas of different meso-components during the load process had obvious abnormal changes; the arrangement of biotite had the best order in initial granite; the regions of quartz and feldspar were more ordered than those of biotite in the whole compression process. The findings in the current study may be used as a reference for the investigation of the deformation/failure mechanism of rock materials.