屈曲型岩爆的发生机制及其时效性研究

Occurrence mechanism and time-dependency effect of buckling rock burst

为分析深部巷道围岩层裂薄板结构的形成机制和屈曲型岩爆发生的力学机理,采用数值模拟方法对深部巷道开挖过程中围岩主应力的分异演化规律进行了研究。基于三参量黏弹性本构关系,以屈曲型岩爆的层裂薄板结构为力学模型,推导出了二向受力下屈曲型岩爆的压屈时效方程,探讨了不同应力状态下屈曲型岩爆的时效特征。结果表明:在以垂直应力为主导的巷道在掘进过程中,巷道顶部和底部的主应力水平在逐步减小,岩体能量逐步释放;而巷道两侧边墙的主应力出现严重的分异现象,切向应力变大而轴向应力减小,岩体能量向两侧转移并大量积聚。以水平应力为主的巷道在掘进过程中,围岩应力状态的演化过程及能量积聚特征与此相反。围岩层裂薄板结构形成后,在切向应力和轴向应力的二向应力作用下发生蠕变弯曲变形,经过一段时间,当变形达到某一限值时,层裂薄板结构就会发生屈曲失稳破坏并释放岩体内积聚的弹性变形能,产生延迟岩爆现象。

To analyze the formation mechanism of slabbing thin plate in surrounding rock and the mechanical mechanism of bulking rock burst, the differentiation law of principle stresses during the deep roadway excavation was studied by numerical simulation. Based on three-parameter viscoelasticity constitutive relationship and the slabbing thin plate mechanical model for buckling rock burst, the buckling time-dependency equation of buckling rock burst under two dimensional stress state was theoretically derived, and the time-dependency features of bulking rock burst under different stress states were discussed. Simulated results indicate that for the roadway where vertical geo-stress is greater than horizontal geo-stress, the principle stresses decrease and the rock energy releases gradually in the roof and floor with the excavation process, while the principle stresses in sidewalls appear to be largely different, the tangential stress increases while the axial stress decreases in sidewalls where the rock mass energy accumulates massively. On the contrary, for the roadway where horizontal geo-stress is greater than vertical geo-stress, the differentiation evolution process of stresses and the characteristics of energy accumula tionare the opposite. The results illustrate the mechanism of delayed rock burst, that is, when the slabbing thin plate structure in surrounding rock forms, the thin plate starts to bend and creep under the action of two-dimensional stress state, after the deformations reach to a limited value in a period of time, the slabbing thin plate structure will bulking fail and release massive elastic strain energy simultaneously.