Experimental and numerical study on rock burst triggering mechanism via spatiotemporal evolution of stress flow

To address the prevention and control of rock burst disasters in deep coal mines, this study focuses on the spatiotemporal evolution mechanism of mining-induced stress, introducing the novel concept of “stress flow” to characterize dynamic stress redistribution behavior. Through integrated laboratory similarity simulation tests and combined finite-discrete element method (FDEM) numerical modeling, the characteristics of stress flow during coal-rock failure and its triggering mechanism for rock burst were systematically investigated. The experiments The tests took a rock burst-prone coal seam in a coal mine as the prototype. Based on similarity theory, coal-rock-like similar materials were prepared. A steel frame model was used to simulate the in-situ stress environment, and stepwise loading/unloading of hydraulic jacks was employed to simulate the mining process. Meanwhile, 50 sets of strain rosettes and 14 sets of pressure cells were arranged to monitor the evolution of stress gradients. The results reveal that during the loading phase, the stress gradient changes gently, and the model remains stable without obvious damage. During the unloading phase, the stress gradient increases significantly, reaching a maximum of 270 kPa/m, which is strongly correlated with coal-rock failure, validating stress flow as a precursor indicator for rock burst. Numerical simulations reproduced the entire process of stress concentration in roadway surrounding rock, yielding of joint elements, and fracture propagation. It reveals that stress flow induces rock bursts through the acceleration of energy accumulation rate and the positive feedback mechanism of “failure-stress redistribution”, i.e. initial failure triggers secondary distribution of stress gradients, forming a chain reaction, which is consistent with the energy release law of the Griffith fracture criterion. The study establishes the stress gradient variation rate as a critical criterion for rock burst initiation. By integrating the temporal evolution and spatial gradient distribution of stress, the stress flow theory establishes a quantitative correlation between the spatiotemporal evolution of mining-induced stress and rock bursts, providing new ideas and theoretical support for dynamic evaluation of rock burst risk.