Study on uniaxial compression damage evolution of soft coal briquette based on speckle number

In order to quantitatively analyze damage evolution characteristics of soft coal briquette during compression process, the digital image correlation metho d was applied to process analysis on surface digital images collected from uniaxial compression test process of cubic coal briquette specimens. A comparison analysis was conducted on damage evolution characteristics of different coal samples. With the speckle number as datum value, the speckle damage variation DIwas provided a nd applied to the stage study on damage characteristics of coal samples. A comparison with the area damage variation Ds was conducted. The results showed that und er the same condition of strain, the speckle damage variation obtained based on the VIC System was higher than the area damage variation and a more detail and cert ain representation could be made on damage boundary and micro-damage. The load curves of different strength coal samples would be different and could have a simil ar law. The higher strength of coal samples, the lower damage variation would be and on the contrary would be higher. The damage variation Di curves of speckles wou Id have mutual corresponded relationships between the damage variation Di curves of speckles and could reflect damage inoculation, damage sprouting, damage devel opment, damage increasing and until full failure process of coal samples. On the speckle damage variation DI curves, Point C1 could be a symbol from elastic to plastic during compression process of coal samples. The speckle damage variation could explain the damage evolution law of coal samples.