不同应力比下砂岩时滞变形破坏特征研究

Study on Time-Dependent Deformation Properties of Sandstone Under Different Axial Stress

高地应力环境下地下洞室中的硬质围岩在开挖过程中极易发生时滞型岩爆.针对地下洞室开挖后围压的实际应力状态,以细砂岩为研究对象开展不同应力水平下的时滞变形破坏试验,并基于分形理论定量描述了破坏后宏观碎屑和破坏断面微观结构的分形特征.研究结果表明:在高应力水平下砂岩表现出显著的时滞变形特征,时滞变形段持续时间随应力比增加呈下降趋势,两者间呈指数函数关系;基于分形理论,通过粒度-数量、质量-粒度、几何参数-数量、盒数维数法等方法计算宏微观分形维数可知,时滞变形破坏程度与分形特征相关性显著,宏微观分形维数随破坏程度增大呈线性增加.研究结果可为阐明岩体时滞变形破坏机理提供一定参考价值.

During the deep underground excavation of hard brittle surrounding rock,time-dependent rockburst frequently happens in high geostress environment.The time-dependent uniaxial compressive test for sandstone was performed to study the failure and fractal characteristics of time-dependent deformation under different stress ratio.The results indicate that sandstone have obvious time-dependent characteristics under high stress level.The duration of time-dependent deformation stage deceases with the increase of stress ratio,and the relationship between them can be described by an exponential function.Based on fractal theory,the fractal dimension is calculated by the methods of particles-quantity,mass-particles,length-quantity,box number dimension,etc.It can be seen that damage degree and dimension have a positive correlation,and macroscopic and mesoscopic dimension increases linearly with the increase of damage degree.The research results could be used as a theoretical reference to study the time-dependent failure mechanism of rock mass.