Properties of non-uniform deformation evolution of rock under uniaxial cyclic loading and unloading

In order to study the mechanic responding mechanism of rock materials under cyclic loading and unloading, uniaxial cyclic loading and unloading tests were carried out to investigate the non-uniform deformation evolution processes of granite specimens. The deformation images of specimens during the tests were collected by CCD camera and based on the digital speckle correlation method,the non-uniform deformation,the evolution laws of the characteris- tic parameters of the localization during cyclic loading and unloading were analyzed. The research results show that: With the increase of cycle numbers,the non-uniform deformation is more and more obvious. The statistical index Sw of non-uniform deformation increases with the increase of loading stress,and increases with the increase of cycle num- bers. After the localization of a specimen appears,the extrusion displacement and the influence width of the localization band all increase with the increase of stress and cycle numbers in the subsequent cycles.