Digital features of main constituents in granite during crack initiation and propagation

摘要

The purpose of this study is to investigate the digital features of various constituents on granite specimen in the crack initiation and propagation process. The test video image photographed during laboratory uniaxial compression test and digital image processing techniques were used to conduct this study. The video image was first converted into the format easily recognized in programming. A multiple-object tracking technique was then developed to detect the locations of the individual cracks at any time. The initiation of each crack was determined by the occurring instant of the bounding box including the cracks. The length, width and area of each crack at any time were thereafter recorded. The relation of the propagation process with digital features of the constituents in various locations was furthermore investigated. It shows that two cracks propagated respectively along the vertical and horizontal directions as uniaxial compression test was performed; a limit box technique can be used to determinate the initiation instants of the multi cracks on the specimen surfaces; during propagation, the width of the cracks increased quickly just after initiation, and then fluctuated around a magnitude until the completely failure of the specimen; the constituents near the crack would split as the crack initiated; the shape features of biotites, feldspar and quartz changed in different manners during crack's initiation and propagation. The technique presented herein may be referable in investigating the failure mechanism of rock materials. (C) 2017 Elsevier B.V. All rights reserved.