不同卸荷应力路径下砂岩时滞变形破坏特征研究

Research on the time-lagged deformation properties of sandstone under different unloading stress paths

地下工程中高地应力赋存环境下的脆硬性岩体在开挖卸荷过程中极易发生时滞型岩爆。通过开展不同卸荷应力路径下考虑围压卸荷速率及卸荷量影响的砂岩三轴时滞变形破坏试验及细观检测分析,探讨不同影响因素作用下的的砂岩时滞变形破坏特征。研究结果表明:不同卸荷应力路径下,时滞变形段总时间均随围压卸荷速率v3先增大后减小,而随围压卸荷比V_(σ)则呈现持续减小的趋势,但升轴压卸围压条件下时滞变形段总时间显著大于恒轴压卸围压,结合试样宏观破坏特征可知,升轴压卸围压应力路径下试样时滞变形破坏程度更高。此外,利用SEM+EDS进行断面特征定量分析表明,不同影响因素作用下的断面矿物颗粒特征与时滞变形段总时间密切相关;最后,结合重整化群理论,建立基于logistics函数的分阶段损伤本构模型,并计算验证模型的合理性。研究结果对于时滞型岩爆的孕育机制研究具有一定的指导意义。

With the deep underground excavation of hard brittle surrounding rock,time-lagged rockburst frequently happens in high geostress environment.Considering the influence effect of unloading stress path,triaxial time-lagged deformation failure test and scanning electron microscopy(SEM)have been performed under different unloading confining pressure rates and different unloading confining pressure degree.A series of tests is to study the time-lagged deformation and failure characteristics of sandstone under different influence factors.The results indicated that the total time of time-lagged deformation stage exhibited increasing and then decreasing trends with the confining pressure unloading rates,and it exhibited decreasing trends with the confining pressure unloading levels.However,compared with unloading confining pressure with constant axial stress tests,the total time of time-lagged deformation stage under unloading confining pressure with loading axial stress tests was longer.Based on this and combining macroscopic observations,the time-lagged deformation failure was more significant under unloading confining pressure with loading axial stress tests.Additionally,through SEM image observation and EDS analysis,it indicated that mineral debris on fracture surface were closely related to the total time of time-lagged deformation stage under different influencing factors conditions.Finally,according to renormalization group theory,the staged damage constitutive model based on logistics function was established,and the effectiveness and rationality of model was proved.These research results can be used as a theoretical reference to study the development process of time-lagged rockburst.