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| A novel rockburst proneness index based on maximum energy dissipation rate |
| ZHANG Rujiu1，ZHANG Yanjie2，GAO Tong3，LI Mei2，LIU Yaoru1，ZHANG Kai1 |
(1. State Key Laboratory of Hydroscience and Engineering，Tsinghua University，Beijing 100084，China；2. Yunnan Dianzhong Water Diversion Engineering Co.，Ltd.，Kunming，Yunnan 650000，China；3. Yunnan Water Diversion Project Construction
Administration，Kunming，Yunnan 650051，China) |
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Abstract Rockburst proneness evaluation provides a basis for rockburst risk assessment in deep tunnels. Based on energy dissipation characteristics of the complete stress-strain curve of rocks under uniaxial compression，a new evaluation index for rockburst proneness，the maximum energy dissipation rate(the maximum value of time derivative of the dissipated energy density)，was proposed. The rationality of proposed index was explained from three perspectives：stability criteria，experience，and definition of rockburst proneness. To quantitatively calculate the proposed index，an elastic-brittle-damage constitutive model considering void compaction and initial damage was established. To verify the applicability of the proposed index and damage model，uniaxial compression and cyclic loading and unloading tests were conducted on four different rocks(basalt，granite，limestone，and sandstone) under rigid and flexible testing machines. Based on the orthogonal tests，correlation analysis，and range analysis，the internal relationship between the proposed index and other rockburst proneness indices was revealed. The major findings are as follows. (1) There exists a maximum energy dissipation rate in the post-peak stage of rock stress-strain curve，which can be used as an inherent stability indicator to evaluate rockburst proneness. The advantage of this indicator is that it can comprehensively consider the pre-peak energy storage and consumption characteristics and post-peak characteristics. (2) The proposed elastic-brittle-damage model effectively describes the nonlinear mechanical behavior and intrinsic energy evolution characteristics of brittle rock(including input energy density，elastic strain energy density，and dissipated energy density). The theoretical curve is in good agreement with the experimental values，and the proposed maximum energy dissipation rate index can be accurately calculated using proposed model. (3) The calculation results of the maximum energy dissipation rate index for different rocks are consistent with the actual rockburst intensity observed in the experiment，verifying the reliability of proposed index. (4) Among the energy-based rockburst proneness indices，the proposed index has the strongest correlation with residual elastic energy index(with a correlation coefficient of 0.940)；the proposed index considers the degree of influence of rock brittleness on rockburst proneness more reasonably. The research method adopted in this study provides a new approach for proposing rockburst proneness indices and analyzing their interrelationships，and the research results provide a scientific basis for the reasonable evaluation of rockburst proneness.
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