深部循环荷载下花岗岩损伤变形与细观结构分析

Analysis of damage deformation and mesoscopic structure of granite under deep cyclic loading

通过对花岗岩进行不同围压损伤控制的三轴等幅循环荷载试验,采用核磁共振技术,对岩石损伤变形和细观结构特征进行了分析。结果表明:1)当围压从50 MPa增大到120 MPa时,试样累计塑性应变和应变损伤参数整体上呈增大趋势;2)随着循环次数增加,试样轴向累计塑性应变逐渐增大,径向和体积累计塑性应变呈阶段增长趋势,而塑性应变增量呈先急剧衰减后趋于稳定的阶段现象;3)在围压一定条件下,随着循环次数增加,试样轴向应变损伤参数减小,体积应变损伤参数增大,径向应变损伤参数先增大后减小;4)循环加卸载后,试样的T2谱曲线由三峰结构变为双峰结构,其细观结构主要表现出大孔隙数量增多、孔径增大以及整体孔隙度大幅升高的特征。

Through triaxial constant amplitude cyclic loading tests of granite under different confining pressures and nuclear magnetic resonance technology,the damage deformation and meso-structural characteristics of rock specimens were analyzed.The results show that:1)When the confining pressure increases from 50 MPa to 120 MPa,the cumulative plastic strain and strain damage parameters of specimens increase as a whole;2)With the increase of the number of cycles,the axial cumulative plastic strain of specimens increases gradually,while the radial and volumetric cumulative plastic strains increase in stages.The increment of plastic strain decreases sharply first and then tends to be stable;3)Under a certain confining pressure,the axial strain damage parameters of specimens decrease,the volume strain damage parameters increase,and the radial strain damage parameters first increase and then decrease with the increase of the number of cycles;4)After cyclic loading and unloading,the T2 spectrum distribution curves of specimens change from three-peak structure to two-peak structure,and the meso-structure mainly shows the characteristics of increasing the number of large pores,pore size and overall porosity.