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应力流时空演化致冲机制的试验与数值研究

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

  • 摘要: 针对深部煤矿冲击地压灾害防治需求,聚焦采动应力时空演化机制,创新引入“应力流”概念表征应力动态重分布行为。通过实验室相似模拟试验与有限元−离散元耦合(FDEM)数值模拟相结合,系统研究了煤岩破裂过程中应力流特征及其致冲机理。试验以某煤矿冲击地压煤层为原型,基于相似理论制作类煤岩相似材料,采用钢架模型模拟地应力环境,通过千斤顶分级加卸载模拟开采过程,同步布设50组应变花与14组压力盒监测应力梯度演化。结果显示,加载阶段应力梯度变化平缓,模型稳定无明显破坏;卸载阶段应力梯度呈显著突增特征,最高达270 kPa/m,且与煤岩破坏呈现强相关性,验证了应力流可作为冲击前兆指标。数值模拟再现了巷道围岩应力集中、节理单元屈服及破裂扩展过程,揭示应力流通过能量积聚速率加速与“破坏−应力重分布”正反馈机制诱发冲击地压,即初始破坏引发应力梯度二次分布,形成连锁反应,符合Griffith断裂准则能量释放规律。研究表明,应力梯度变化率是冲击启动的关键判据,应力流理论通过统筹应力时间演化与空间梯度分布,建立了采动应力时空演化与冲击地压的定量关联,为冲击危险性动态评价及主动防控提供了新思路与理论支撑。

     

    Abstract: 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.

     

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