Self-Organized Criticality Characteristics And Rock Burst Tendency Of Rock Mass During Rock Failure Process

In projects of deep resource exploitation and underground space expansion,the stability of rock pillars has always been a problem faced by actual projects.Due to the deep rock masses are in a special geo-mechanical environment of “three highs and one disturbance”,the phenomenon of instability of natural or artificial rock masses occurs from time to time,and basically has a positive correlation with depth,and Poses a serious threat for safe mining of resources and security activities of human.Therefore,the failure law of deep rock mass under uniaxial compression is not only important for development of rock mass mechanics theory,but also has important strategic significance for the feasibility of resource development and sustainable development.In this paper,the different type of rock mass was taken as the research objects.Combining with theoretical analysis and laboratory tests,the acoustic emission test of cubic specimens and cylindrical specimens under uniaxial compression was carried out.According to the statistical results of tests,the macro-rupture morphology during the entire destruction process,the power-law characteristics between microscopic acoustic emission energy rate and impact number rate,the cusp catastrophe model,and the propensity grades of the rock-bursts of every specimen were discussed.Through researching the self-organized critical law of the rock mass failure process,the fracture mechanism from the perspective of non-linear scientific theory could be analyzed.Meanwhile,some guiding suggestions for practical engineering could be provided.The main work and conclusions of this paper were as follows:(1)Through uniaxial compression tests on cubic and cylindrical mortar specimens,concrete specimens,red sandstone specimens and granite specimens,the results show that the macroscopic progressive rupture process of specimens is a dynamic attractor with a weak structural surface.From the disordered stable state of low energy values to the ordered unstable state of high energy values,a “direction” self-organizing process could be proved.(2)Acoustic emission instruments are used to collect acoustic emission energy and impact rates for specimens of different sizes.Based on the power-law properties of magnitude and frequency in the Gutenberg-Rich law,the power-law behavior of the rock breaking process is similarly studied and based on rock.The cusp catastrophe theory establishes the catastrophic catastrophe model of each test piece to quantitatively predict the moment of rock instability.The result of the research shows that whether the cube specimen or the cylindrical specimen,the acoustic emission energy rate and the impact rate of the acoustic emission activity from the beginning of compression to the adjacent destruction are better obeyed by the power law distribution,and interpreted from the energy perspective.The self-organized critical behavior of rock fractures.Secondly,according to the mutation epidemic criterion of each mutation model obtained by least-squares fitting,it can be seen that the cubic mortar specimen,the cubic red sandstone,and the cubic granite were destabilized at the 321 s,743s,and 831 s,respectively,and the cylindrical concrete,the cylindrical red sandstone and cylinder granite were destabilized at the 256 s,264s and 420 s,respectively,and all were consistent with the destabilization moments recorded during the test.(3)According to the whole stress-strain curve under the acoustic emission test,the rock bursting tendency analysis criteria were established based on the criteria of the rock impact energy index.The results show that the mean values of rock burst impact energy index for cubic mortar,red sandstone and granite specimens are 5.76,24.87 and 25.25,respectively,while the mean values of rock burst impact energy index for cylindrical concrete,red sandstone and granite are 16.97,21.33 and 23.90,respectively.The inclinations are consistent with the catastrophic phenomena of debris and lumps presented in the experiment,revealing that the higher the strength in the deep rock mass,the greater the tendency of the rock-burst to occur.