花岗岩中多条裂隙的萌生扩展过程研究

Investigation of the initiation and propagation of multi-cracks in granite

岩石破坏通常是不同时刻多条裂隙萌生扩展的过程,可以使用室内试验视频图像和多目标跟踪技术进行研究。使用MATLAB编程平台,将试验视频图像转化为编程可读形式,选定视频图像中含有裂隙萌生扩展过程的样品范围,通过编制多目标跟踪函数对试样中的裂隙对象进行目标检测和跟踪,根据裂隙限位框出现的时刻确定了裂隙的起裂时刻,进而确定了任一时刻多个裂隙的分布位置,分析了裂隙的长度、宽度、面积随时间的变化过程,探讨了跟踪参数(最小背景比、开启操作的开启面积)对目标裂隙跟踪结果的影响。结果表明,最小背景比越大,裂隙跟踪时间越短;开启面积越小,裂隙变化的跟踪越敏感。本方法能够同时跟踪多条裂隙的起裂与变化过程,可为岩石的变形破坏过程研究提供一条新的研究途径。

In general, rock failure is a process of the initiation and propagation of multiple cracks in rocks at different instants. The laboratory test video images and multiple-object tracking technique were used to investigate the initiation and propagation of multiple cracks in rocks in this study. The video images were firstly converted into the video formats which are easily recognized in programming. The sample range containing cracks were extracted using a MATLAB code. A multiple object tracking function was conducted to detect and track the cracks on the sample surface. The crack initiation was confirmed by the appearance moment of the bounding box of the crack in the video images. The locations of the multiple cracks were thereafter determined. The length, width and area of the cracks and their changes with time were also analyzed. The effect of the multiple-object parameters, mainly including the minimum background ratio and area of the openness operation, were further examined. The results show that the tracking time is shorter as the minimum background ratio becomes greater; the changes of the cracks are more sensitive as the openness area is smaller. The technique presented herein may be used to track the multiple cracks at the same time and provides a new routine to examine the deformation/failure process of rock materials.