对滇藏铁路三江段的花岗岩进行了单轴和常规三轴压缩试验，研究了岩石在不同围压条件下的变形特性及其损伤演化规律。试验结果表明：该岩石压缩变形过程中，内部裂隙的演化经历了无起裂、起裂并稳定扩展、加速扩展、扩展变缓以及扩展停止5个阶段，且围压对岩石变形特性有显著影响。在此基础上，提出了基于有损微元生成的损伤演化模型，建立了三轴压缩条件下岩石应变软化损伤本构模型。该模型能够统一描述岩石峰前及峰后全部变形特性及其损伤演化规律，且损伤方程形式简单、参数物理意义明确。理论结果和试验数据具有很好的一致性，且参数分析结果也表明了该模型的合理性。

The uniaxial and conventional triaxial compression tests were conducted on granite from Sanjiang region of Yunnan-Tibet railway in the laboratory. The deformation characteristics and the damage evolution law of rocks were examined under different confining pressures. The results show that the internal cracks experience five stages during the compression deformation process, including no crack, crack initiation and stable propagation, crack accelerating propagation, crack decelerating propagation and crack termination. In addition, confining pressure significantly influences deformation characteristics of rock. Based on the above analysis and the damage model of micro units, a damage constitutive model is developed under the triaxial compression condition. The proposed model has a simple function form and distinct physical meaning parameters, which can be used to describe both the pre-peak and post-peak deformation characteristics of rocks. Furthermore, theoretical results obtained by this model are in good agreement with experimental results in the literature. The rationality of the model is verified by the parameter analysis.