热处理北山花岗岩变形特性试验与损伤力学分析

温度与荷载共同作用下岩石力学行为和损伤特性的研究，对于深入认识高放废物处置库围岩在热-力耦合作用下的渐进破坏规律具有重要意义。以国内高放废物处置库预选区甘肃北山花岗岩为研究对象，通过开展不同热处理温度后的物理力学性质测试，并借助偏光显微和X射线衍射细微观分析手段，对其宏观变形、损伤演化以及破坏特征开展了研究。研究结果表明：随着热处理温度的升高，质量、密度、纵波波速和峰值强度总体呈下降的趋势，而体积和峰值应变则逐渐增大，1 000 ℃时不同围压下的峰值强度分别减小了77.70%、57.28%、37.33%及33.97%，峰值应变分别增加了196.37%、115.27%、105.13%及90.38%。在低温、低围压下三轴压缩过程中北山花岗岩的损伤发展迅速，破坏形式以张拉劈裂为主，且试样破坏后极为破碎，在破坏面附近存在多条贯通的轴向裂纹；随着温度和围压的增大，北山花岗岩的变形由脆性向塑性转变，破坏形式都是陡倾角的剪切破坏。

Deformation characteristics tests and damage mechanics analysis of Beishan granite after thermal treatment

The study of deformation behavior and damage characteristics under coupled thermal-mechanical loading is crucial to comprehensively understanding of the progressive failure law of rock mass in the high-level radioactive waste repository. The aim of this study is to investigate the macro-deformation behavior, damage evolution process, and failure characteristics of Beishan granite after thermal treatment. Granite samples are from Gansu Province a potential site for China's HLW disposal. Triaxial compression tests coupled with transmitted cross-polarized light and X-ray diffraction (XRD) micro-observation are performed on Beishan granite samples under different confining pressures. The mass, density, P-wave velocity and peak strength gradually decrease, while the volume and the peak axial strain slowly increase with the increase of temperature. Accordingly, the peak strengths decrease by 77.70%, 57.28%, 37.33% and 33.97% respectively, while peak strains increase by 196.37%, 115.27%, 105.13% and 90.38% at the 1,000 ℃ under different confining pressures. At the low temperatures and low confining pressures, the failure form of sample is characterized by tensile split, and a number of coalescent axial fissures around fracture surface are observed. The deformation pattern transforms from brittle fracture to plastic shear deformation with steep dip as the temperature and confining pressure increase.