In order to investigate the size effect and reason of rock fracture toughness, the split loading test was carried out in the GCTS rock mechanics testing machine using the center-cracked circular disc (CCCD) samples with diameters of 50 mm, 100 mm, 150 mm and 205 mm, respectively. The lengths of fracture process zone (l_FPZ) were determined by the maximum normal stress criterion. The size effect of the l_FPZ , fracture toughness test value (K_Ic), and fracture energy (G_f) were analyzed. The influence of the l_FPZ on the size effect of the K_Ic was revealed. The crack growth paths and failure characteristics of the samples were discussed. The results show that the l_FPZ and the K_Ic increase linearly with the sample size, and there is obvious size effect within the range of the test. The K_Ic and the l_FPZ do not always increase linearly with the size in a larger size range, but gradually stabilize by extrapolation analysis. The l_FPZ increases with the size, which means the release of stored energy increases with the size corresponding to the size effect of the G_f, and in turn leads to the size effect of the K_Ic. It is helpful to deeply understand the cause of the size effect reason of rock fracture toughness.

为了研究岩石断裂韧性的尺寸效应和原因，在GCTS岩石力学试验机中使用直径为50 mm，100 mm，150 mm的中心裂纹圆盘（CCCD）样品进行了劈裂载荷试验和205毫米。断裂过程区（的长度升_FPZ）由最大正常应力准则来确定。所述的尺寸效应升_FPZ，断裂韧性测试值（ķ _Ic的），和断裂能（G ^ _˚F）进行了分析。的影响升_FPZ上的尺寸效应ķ _Ic的被揭示了。讨论了样品的裂纹扩展路径和破坏特性。结果表明，l _FPZ和K _Ic随样本大小线性增加，并且在测试范围内有明显的大小效应。该ķ _Ic的和升_FPZ并不总是与较大尺寸范围的大小呈线性增长，而是通过外推分析逐渐趋于稳定。的升_FPZ与大小，这意味着与对应于所述的尺寸效果的大小存储的能量的增加而增加释放ģ _˚F，和在又导致的尺寸效应ķ _Ic的。深入理解岩石断裂韧性尺寸效应原因的原因是有帮助的。