An experimental investigation on the damage of granite under uniaxial tension by using a digital image correlation method

• Damage evolution of granite under uniaxial tension was investigated by using the digital image correlation method.
• A parameter was proposed to describe the average gradient of the tensile strain.
• The experimental results showed that the damage was related to the strain as well as to the strain gradient.

This paper presents an experimental investigation of the damage mechanisms of granites under uniaxial tension. The displacement distribution and surface tensile strain of the specimens were measured by using a digital image correlation (DIC) method. A substantially large strain localization region emerged on the surface of the specimens before the tensile stress approached its ultimate value; subsequently, this strain localization region coincided with the final crack. Based on the measured tensile strain, a parameter was proposed to describe the average gradient of the tensile strain. This parameter was found to be much larger near the crack than in the other regions. Experimental results showed that the damage was related to the strain as well as to the strain gradient. These results may provide a practical foundation for a new gradient damage theory for rocks under tensile loading.