三轴压缩蠕变试验下石英云母片岩各向异性蠕变特性研究

对石英云母片岩进行三轴压缩蠕变试验，研究丹巴水电站石英云母片岩的三轴蠕变特性及其各向异性特性。按轴向荷载与层理面关系加工成平行组和垂直组2组试件，开展分级加载方式进行不同围压条件下的蠕变试验。试验研究表明，石英云母片岩具有蠕变特性，包括瞬时变形、衰减蠕变、稳定蠕变和加速蠕变阶段；采用带Kachanov蠕变损伤律的蠕变模型来描述石英云母片岩的蠕变特性，并进行蠕变参数辨识，拟合结果显示此模型能很好地描述石英云母片岩的蠕变特性；根据试验结果获得2组试件的长期屈服强度、破坏形态、瞬时变形参数和稳定蠕变速率，分析表明石英云母片岩的蠕变力学特性具有明显的各向异性特性。层理面与轴向荷载垂直的试件较层理面与轴向荷载平行的试件的强度、弹性剪切模量、体积模量和黏性系数相对较大，表现出较高的抗变形和抗破坏能力；平行组以剪切破坏为主，垂直组破坏时出现侧向鼓胀现象，显示出延性破坏的特点；2组石英云母片岩试件的瞬时应变量和稳定蠕变速率都随着应力水平的提高而增大。

Anisotropic rheological properties of quartz-mica schist under triaxial compression creep test

Triaxial compression creep tests on the quartz–mica schist from Danba, China, are carried out to illuminate the schist’s anisotropic creep characteristics. Samples are divided into two sets by the axial load direction, which is perpendicular or parallel to the rock bedding plane. Creep tests under different confining pressures used the multistage loading mode, which shows the creep variation of the quartz–mica schist, including instant deformation, attenuation creep, stable creep, and acceleration creep. A creep model with the Kachanov creep damage rule is adopted to describe the acceleration creep stage, and to estimate the rock creep parameters of the quartz–mica schist. The good agreement between the fitting and test curves indicates that this model can suitably describe the creep properties of a quartz–mica schist. Long-term yield strength, fracture morphology, instantaneous deformation parameters, and steady-state creep strain rate based on the results from the two sets of tests show that there are significant anisotropic creep properties in the quartz–mica schist. The relatively higher strength, shear modulus, bulk modulus, and viscosity of these samples, in which the bedding plane is perpendicular to the axial load, show that these samples perform better in terms of anti-deformability and damage resistance compared with the parallel sample set. The samples in which the bedding plane is perpendicular to the axial load mainly have shear failure modes; the other sample set show lateral expansion when the samples are damaged. The instantaneous deformation and stable creep rate of both test sets increase with increase of stress level.