Abstract: The failure process of rock containing single fissure is investigated under laboratory environments. Integrated with particle imaging velocity(PIV) and strain measurements during experiments, displacement vector of samples during failure process is identified and moreover the stress on the surface of samples is calculated based on finite element(FE) method. The k-value, which is defined as the ratio of concentration stress to peak stress of samples during experiments, is proposed to identify the stages of deformation and failure process of rock containing single fissure. Then the stress field characteristics at each stage are analyzed. The results show that: at first, k-value increased and remained constant. Then k-value fluctuated and increased dramatically with the increasing of axial strain. Several important stress thresholds are acquired according to the variation regularity of k-value; the closure stress σcc , the initiation stress σci , the damage stress σcd , and the values of them are 0.13-0.17, 0.48-0.59, 0.80-0.92 times of peak stress σp respectively. The k increased dramatically after fluctuated; macroscopic cracks are observed in the region where stress concentrated. Macrocrack distribution areas are consistent with stress-concentration areas. This study will help people to understand the stress field variation of cracked rock and provide a new way to divide the deformation and failure process of cracked rock.

Key words: ratio of concentration stress to peak stress, cracked rock, uniaxial loading, PIV particle imaging velocity