中文摘要：

针对岩石单轴压缩试验中存在的加载条件敏感性的问题，采用自行开发的二维弹塑性细胞自动机模拟系统EPCA^2D，对不同尺寸的非均质岩石试样进行单轴压缩破裂过程模拟，研究不同的加载条件对岩石宏观变形行为和破裂模式的影响。结果表明，均质性相同的岩石试样在单轴压缩破裂过程中所表现的尺寸效应和形状效应现象与岩石本身的非均质性关系不大，加载垫板与试样之间力学性质的差异是造成岩样单轴压缩破裂过程尺寸效应和形状效应的根本原因，模拟结果再现了典型的试验现象。通过研究加载垫板与试样端部之间不同的摩擦情况，结果表明，即使试样端部存在较小的摩擦，仍然会造成岩样单轴强度和变形特性的离散性。因此，通过减小试样端部的摩擦来提高岩石单轴压缩试验质量是不可靠的。

英文摘要：

Based on the phenomenon of loading condition sensitivity, which exists in the uniaxial compression tests of rocks, a numerical study is conducted to investigate the effect of loading conditions on the deformation behaviors and failure patterns of rocks with different sizes and shapes under uniaxial compression, using a self-developed numerical code EPCA^2D. It is concluded that, for rocks with the same homogeneity, the size and shape effects are mainly caused by the mismatch of mechanical properties between rock specimen and loading platen. The simulation results agree with the experimental phenomenon well. Different friction conditions between loading platen and specimen＇s ends are considered in the simulation. Results indicate that the discreteness of uniaxial strength and deformation behaviours with different frictions exist even when the frictions are reduced to a very low value. Therefore, it is unfavourable to improve the experimental quality by reducing the frictions.