Parallel computing of disturbance response instability theory of rockbursts

At present, theoretical analyses of rockbursts have entered into the quantitative analysis stage from the qualitative analysis stage. The critical stress of the roadway surrounding rock has become the important basis for safe assessment of the roadway. Theoretical breakthrough becomes extremely difficult due to the extreme complexity of rockbursts. Calculation of the critical stress of the roadway surrounding rock based on the analytical formula is not applicable for the complex situation, such as non-circular roadway, non-hydrostatic pressure and complex strata structures. Combination of theories of rockbursts and numerical simulation possesses a broad application prospect, promoting theories of rockbursts to a further actual application. This is an extremely valuable development direction. Achievement of this aspect depends on the rapid development of the numerical technologies. In this paper, the self-developed advanced parallel computing system of strata movement (StrataKing, a parallel computing method in nonlinear fracture mechanics base on a hybrid Lagrangian and discrete element method) and the disturbance response instability theory of rockbursts was combined. A numerical method for the disturbance response instability theory of rockbursts for the circular roadway was proposed firstly. The idea of the method is that the Ⅱ-type fracture energy in nonlinear fracture mechanics is seen as a moderate variable. Thus, the relation between the critical stress of the circular roadway surrounding rock under hydrostatic pressure and the burst energy index was established. To obtain the numerical solution of the burst energy index, an ideal numerical test for a rock specimen in uniaxial compression, which is subjected to a single shear fracture, was conducted so that effects of other factors on the relative straight portion of the post-peak stress-strain curve can be neglected. For a high-angle shear fracture, the result for the non-standard rock specimen was converted into that for the standard rock specimen. The converted burst energy index is in the range of 0.17−13.52, falling into the survey data of 131 rockburst coal mines in China. The numerical critical stress of the circular roadway surrounding rock is 0.4−2.5 times of the analytical result, qualitatively consistent with the survey data (the modified coefficient of the critical stress of the circular roadway surrounding rock is usually greater than 1, even reaching 8) of 20 rockburst coal mines in China. We believe that the roadway surrounding rock subjected to the localized failure has a higher load-carrying capacity than subjected to the uniform failure. Thus, the phenomenon that numerical results are higher than analytical results can be explained. The relation between rockbursts and localization has been discussed, and not for the relation between the disturbance response instability theory and localization in the past. In the present paper, localization was acted as a medium so that a closed relation between the disturbance response instability theory and rockburst was established in terms of the fracture mechanism. StrataKing can provide a powerful support of computing power for safe assessment of roadway surrounding rock in rockburst coal mines.