深部硬岩卸荷流变效应及时滞型岩爆机理

With depth increasing of the underground engineering, rockburst occurs more frequently. Under complex stress environment, mechanism research of rockburst is a key problem that must be solved in deep underground engineering. This project takes the rheological characteristics of unloading hard rocks under high stress as the main line. Mechanism of time-delayed rockburst is investigated, by using and theoretical analysis, laboratory tests and numerical simulation methods. Firstly, space-time evolution of cracks and the deformation field is researched by carrying out hard rocks’ unloading rheological tests. The rheological instability characteristics under different stress conditions is analyzed. Secondly, by using micro-mechanics testing and simulation means, the micro-crack structure feature at different rheological instability modes is studied. The quantitative relation among the heterogeneity, crack distribution fractal dimension and rheological parameters is confirmed. Thirdly, a damage characterization form considering rock’s heterogeneity and crack distribution is proposed, based on which, a new unloading rheological damage constitutive model is established. Finally, a simulation model of chamber excavation in deep rock mass is built based on the new constitutive model, and space-time evolution of the energy filed is researched. The energy inducing condition on rockburst is analyzed, and mechanism of time-delayed rockburst influenced by rheological effect of surrounding rocks is revealed. This research may provide theoretical basis for the prevention and control of time-delayed rockburst.

随着地下工程的逐渐深部化，岩爆灾害愈加频繁，深部复杂应力环境下的岩爆机理研究已成为地下工程亟需解决的关键难题。本项目以高应力下硬岩卸荷流变特性为研究主线，拟采用理论分析、室内试验与数值模拟相结合的手段，对时滞型岩爆机理进行深入研究。首先，进行高应力下硬岩卸荷流变试验，研究岩石微破裂分布及变形场的时空演化特征，分析不同应力条件下的流变失稳特征；其次，采用细观力学测试与模拟分析手段，研究不同卸荷流变失稳模式下的细观微裂纹结构特征，确定岩石均质度、裂隙展布分数维与蠕变参数间的定量关系；然后，提出反映岩石细观非均质特性和裂隙展布形态的损伤表征方法，建立岩石卸荷流变损伤本构模型；最后，进行深部岩体硐室开挖仿真试验，研究围岩能量场的时空演化规律，探寻岩爆的能量触发条件，揭示围岩流变效应影响下的时滞型岩爆机理。本项目研究成果可为深部岩体工程岩爆灾害的预测及防治提供基本的科学依据。

针对深部复杂应力环境下时滞型岩爆问题，本项目进行了不同卸荷路径下硬岩流变试验，揭示了岩石宏观及细观结构能量积聚-释放特征，研究了流变效应下采动应力演化规律，主要结论有：（1）砂岩恒轴压-卸围压和加轴压-卸围压蠕变时，试样侧向蠕变特性更为显著，约为轴向应变的1.8~4.6倍，侧向扩容效应明显；花岗岩双轴卸侧压蠕变时，轴向应变蠕变值随侧压呈先降低后增加的趋势，而侧向应变蠕变值与侧压呈负相关关系；蠕变失稳阶段，剪应变场出现明显的局部化现象，与宏观裂隙位置对应；（2）对于实验室尺度的花岗岩试件，其能量演化可划分为稳定蓄能、缓慢耗能、急速释能三个阶段；随围压增大，应变能转化比呈指数函数减小，应变能极值线性增大，峰前应变能积聚速度线性增大，峰后能量释放呈指数函数减小；相比于云母和石英，长石矿物是能量积聚的主要细观结构；（3）工程尺度围岩卸荷时，煤体内部应变能积聚量及释放速度大于顶底板岩层；随着煤体弹性模量的增大，煤体应变能积聚量及释放速度呈幂函数减小；卸荷围岩冲击动能演化分为冲击启动、急速冲击、稳定冲击和残余冲击四个阶段；煤体冲击动能极值与煤体弹性模量负线性相关，岩体冲击动能极值与煤体弹性模量正线性相关；（4）考虑流变损伤时，随流变时长增加，围岩支承压力峰值呈指数函数降低，应力峰值距煤壁距离呈幂函数增大。本项目研究成果为深部时滞型岩爆防治提供了一定的理论指导。