含初始损伤大理岩的时效变形与破坏试验研究

Experiment Study of Time-dependent Deformation and Failure of Original Damage Marble

为研究大型地下洞室在持续的多次开挖卸荷和复杂应力重分布过程中损伤围岩的时效变形和破坏特性,针对现有岩石流变或时效破坏试验研究未充分考虑试样初始损伤的不足,通过预加载的方式对大理岩构造初始损伤,结合声发射对含初始损伤大理岩进行单轴压缩时效变形和破坏试验及裂纹扩展观测分析,同时对比开展含初始损伤大理岩和完整大理岩的蠕变试验研究。结果表明:1)含初始损伤大理岩单轴压缩时效破坏没有明显的应力峰值点;当临近破坏停止加载保持应力恒定后,其环向应变的增长幅度远大于轴向应变的增长幅度。同步声发射监测揭示体应变的拐点是含初始损伤样发生破坏的先兆。2)三轴蠕变试验中含初始损伤大理岩的轴向和径向应变均大于完整大理岩的轴向和径向应变,体应变结果分析显示含初始损伤大理岩在加载初期即出现体积扩容。3)随着围压的升高无损伤大理岩仍发生剪切型脆性破坏,含初始损伤大理岩从脆性破坏向延性破坏转化,最终呈现"X"型共轭剪切鼓胀破坏。试验研究结果有力地表明含初始损伤大理岩的时效变形与破坏特性不同于完整大理岩,其对更加合理地分析地下洞室长期稳定性具有重要的借鉴意义。

In order to research the time-dependent deformation and failure properties of damage surrounding rock in the process of excavation and under continuous complex loading,a marble was initially damaged by preloading,and uniaxial aging damage compression test combined with acoustic emission and crack propagation analysis were conducted on original damage marble,comparative study on triaxial creep test between initial damage marble and complete one was executed.The results shows that initial damage marble has no apparent stress peaks under uniaxial aging damage compression,keeping stress constant when near to failure,the ring strain amplitude is much greater than the growth of axial strain.Synchronous acoustic emission monitoring revealed that volumetric strain inflection points is the forerunner of the initial damage damage occurred.Both axial and radial strains of initial damage marble are greater than the complete marble under triaxial creep test.Volumetric strain analysis showed that the initial damage marble appears volumetric dilatation at the beginning of the load.With the increase of confining pressure complete marble still come up shear brittle failure,while the initial damage marble transform from brittle to ductile,finally presented the"X"type conjugate shear ballooning failure.The results strongly suggested that the deformation and failure of damaged marble are different from the complete one,which could also provide important guiding significance for the theoretical analysis and the long-term stability of large cavities.