单、三轴及孔隙水作用下黄砂岩破坏力学行为及损伤演化规律研究

Study on failure mechanics behavior and damage evolution law of yellow sandstone under uniaxial triaxial and pore water action

为了探索岩石受力状态及水力耦合下的反馈特征,研究岩石损伤破坏过程中的力学行为及能量演化规律,以黄砂岩单、三轴及孔隙水声发射实验为基础,分析有效应力影响下的强度特征及变形特性,获取全过程的能量转化规律,基于声发射能量推导演化方程,并以此分析不同条件下黄砂岩损伤演化阶段及特征,实验结果表明:有效峰值载荷与有效残余应力与有效围压呈现正相关。随着有效围压的增大,弹性模量呈现线性增大,泊松比与水压力呈现反比特征,压密阶段越来越短,弹、塑性阶段不断延长,扩容点也在不断增大。随着有效围压的增加,主控裂纹越来越规整,线性特征越来越明显,微裂纹越来越少,破裂角度逐步增大;在水力耦合条件下,岩石主破裂更加明显,微破裂随着水压和围压的增加而逐渐递减。通过分析有效正应力和有效剪应力之间的关系,τ-σ破坏强度曲线满足库仑准则。随着有效围压的增大,峰前总能量、弹性能、耗散能、峰后释放的能量及盈余能量均呈现增大的趋势。随着孔隙水压力的增大,盈余能量越来越小,说明高水压能够降低发生动力破坏。基于能量损伤演化方程给出了损伤演化典型的5个阶段,得到了水压力与岩石脆性损伤之间的关系。研究结果对于不同受力状态围岩控制及注水防治灾害具有理论意义。

In order to explore the mechanical behavior and energy evolution law of rock damage and failure under the coupling effect of stress and water,the experiments of single and triaxial pore water pressure on yellow sandstone were carried out,and acoustic emission(AE)monitoring was carried out simultaneously.The strength and deformation characteristics of rock under the influence of effective stress are analyzed,and the energy transformation law in the whole process is obtained.Based on AE energy,the damage evolution equation is deduced,and the damage evolution stages and characteristics of yellow sandstone under different conditions are analyzed.The experimental results show that,there is a positive correlation between effective peak load and effective residual stress and effective confining pressure.The elastic modulus increases linearly with the increase of effective confining pressure.And Poisson’s ratio is inversely proportional to water pressure.As the water pressure increases,the compaction phase becomes shorter and shorter,the elastic and plastic phases continue to increase,and the expansion point is also increasing.Besides with the increase of effective confining pressure,the main control cracks become more and more regular,the linear characteristics become more and more obvious,the micro-cracks become less and less,and the rupture angle is gradually increased.Under the hydraulic coupling condition,the main rock rupture is more obvious,and the micro rupture gradually decreases with the increase of water pressure and confining pressure.What is more,by analyzing the relationship between effective normal stress and effective shear stress,theτ-σdamage strength curve satisfies the Coulomb criterion.With the increase of effective confining pressure,the total energy,elastic energy,dissipated energy,energy released after the peak and surplus energy all show an increasing trend.And as the pore water pressure increases,the surplus energy becomes smaller and smaller,indicating that high water pressure can reduce the occurrence of dynamic damage.Based on the energy damage evolution equation,five typical stages of damage evolution are given,and the relationship between water pressure and rock brittleness damage is obtained.The research results have theoretical implications for surrounding rock control and prevention disasters with water injection in different stress states.