锦屏大理岩卸荷本构模型与数值模拟研究

锦屏二级水电站深埋引水隧洞位于高地应力区，对取自隧洞内的大理岩进行常规三轴压缩试验、峰前卸围压试验。基于大理岩的峰前卸荷试验，研究峰前卸荷条件下岩石的变形、参数及破裂特征，建立峰前卸荷条件下岩石的幂函数型Mohr强度准则，给出数值仿真试验中大理岩的峰前卸载条件，利用有限差分程序FLAC3D建立了数值仿真模型，对模型进行了计算与分析，最后与室内试验结果对比，得到峰前卸荷状态下大理岩力学特性的相关规律。研究结果表明，幂函数型Mohr强度准则可较好地反映峰前卸荷条件下岩石的强度特性；卸围压初期，岩石试件呈现出明显的弹塑性特征；卸荷过程中岩石试件发生破坏时的峰值强度和围压降值随着围压增加而变大。研究结论揭示了锦屏大理岩卸载应力路径下的力学特性，具有一定的理论参考价值。

Research on constitutive model of Jinping marble under unloading conditions and numerical simulation

Deep diversion tunnel of Jinping Ⅱ Hydropower Station is located in a high stress zone; for its surrounding rock, i.e. marble, the conventional triaxial test and pre-peak unloading test are carried out. Based on pre-peak unloading test of the marble, its deformation, parameters and strength characteristics under pre-peak unloading are studied; and a power function Mohr strength criterion which can fit the pre-peak unloading tests appropriately, is established. The conditions of pre-peak unloading in numerical simulation is given. By using finite difference procedure of FLAC3D, a numerical simulation model is established; and it is analyzed and compared with the laboratory test result. Finally, the characteristics of the pre-peak unloading rock mass is acquired. The results indicate that nonlinear Mohr strength criterionis can fit to the strength characters of the rock under pre-peak unloading test; at the beginning of pre-peak unloading test, elastoplasticity characteristics is shown; the peak strength and decline of the confining pressure increases continuously as the confining pressure increase. These conclusions reveal the unloading mechanical properties of marble under high geostress and provide reliable theoretical reference for us.