Abstract: Self-organizing criticality theory provides a new interpretation for the behaviour characteristics and evolution patterns of disordered and non-linear complex systems. Based on this theory, the law of fracture evolution with different rock types was discussed. Considering the influence of body shape on the failure characteristics, uniaxial compression test and acoustic emission (AE) test were carried out on two rock specimens, i.e. cube and cylinder. The acoustic emission information before and after the self-organized critical point during the evolution of rock fracture was analyzed. According to the distributed of the probability density of AE energy, the spatial positioning of AE event and the AE waiting time, and their critical exponent k, productivity exponent α  of after shock distribution, and waiting time distribution exponent δ were analyzed statistically. The results show that the failure processes of both cube and cylinder specimens are self-organization processes from disordered stable state of low energy value to ordered unstable state of high energy value. The body shape has little effect on the self-organization process of its destruction. Comparing with cylindrical specimens, the first phase of cubic specimens from compression to the first critical point of self-organization, volume expansion point, lasts relatively longer, and the self-organization evolution process from the first critical point to the second critical point of self-organization, speak strength point, is also faster. The failure of the cubic specimen is more regular, which is more conducive to failure prediction. Cubic specimen is isotropic in the process of compression, which restricts the development of cracks so the critical index of the whole process of fracture is larger. While the local yield weakening characteristic of cylindrical specimen is obvious, which makes the development of cracks under compression easier and its critical index is smaller. For the productivity exponent α of Omori law of rocks with different sizes, the value α of the second stage of the self-organization evolution of fracture of cubic specimens is greater than 1, while that of cylinderical specimens is less than 1, indicating that the cube specimens have entered the critical instability state before the second critical point. In the large waiting time range (>0.1 s), the critical exponent of the second stage of self-organization evolution of fracture of specimens with different body shapes is larger than that of the first stage, which is consistent with the fact that the frequency of new cracks increases with the self-organization evolution of fracture.

Key words: rock fracture process, self-organizing criticality, acoustic emission energy, power law distribution, critical index