In order to investigate the feasibility and reliability of the three-dimensional particle flow method in simulating the type I fracture toughness test, four types of numerical samples were established by particle flow code PFC^3D: straight crack three-point bending (SC3PB), edge cracked flattened semicircular disc (ECFSD), cracked chevron notched Brazilian disc (CCNBD), and edge cracked flattened ring (ECFR). Three models with different strength parameters (group A, group B, and group C) were established for each type, in which group A parameters are obtained from the concrete model, group B parameters are applied for simulating marble, and group C parameters are for granite. The type I fracture toughness and the failure form of each model are obtained by conducting the numerical test, and the curves of load versus displacement of loading point are recorded. The numerical test results show that, with the same strength parameter, the maximum difference in test results of each specimen type is 0.39 MPa·m^1/2. The K_IC of ECFR specimen is 0.13–0.28 MPa·m^1/2 smaller than that of CCNBD specimen, and the K_IC of ECFSD specimen is slightly higher than that of CCNBD sample. The K_IC of SC3PB specimen is 0.06–0.21 MPa·m^1/2 smaller than that of the CCNBD sample. When the loading rate is less than 0.01 m/s, the effect of loading rate on fracture toughness can be reduced to less than 0.1 MPa·m^1/2.

中文翻译：

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基于粒子流法的类岩石材料I型断裂韧性试验

为了研究三维粒子流方法在模拟I型断裂韧性试验中的可行性和可靠性，使用粒子流代码PFC ^3D建立了四种数值样本：直裂纹三点弯曲（SC3PB），边缘开裂的扁平半圆盘（ECFSD），开裂的V形缺口巴西圆盘（CCNBD）和边缘开裂的扁平环（ECFR）。针对每种类型，建立了三个具有不同强度参数的模型（A组，B组和C组），其中从混凝土模型中获得A组参数，将B组参数应用于模拟大理石，而C组参数则用于模拟大理石。花岗岩。通过数值试验获得了各模型的Ⅰ型断裂韧性和破坏形式，并记录了载荷对载荷点位移的曲线。数值试验结果表明，在相同强度参数的情况下，每种试件的最大试验结果差为0.39 MPa·m ^1/2。该ķECFR样品的_IC比CCNBD样品小0.13–0.28 MPa·m ^1/2，ECFSD样品的K _IC比CCNBD样品小。SC3PB样品的K _IC比CCNBD样品的K _IC小0.06-0.21 MPa·m ^1/2。当加载速率小于0.01m / s时，加载速率对断裂韧性的影响可以减小到小于0.1MPa·m ^1/2。