细观组构特征对含U型切槽岩石梁断裂特性的影响规律

Influence of microstructural features on the fracture characters of rock beams with a U-shaped notch

为了揭示细观组构特征对岩石断裂特性的影响规律,基于临界距离理论,建立含U型切槽岩石梁表观断裂韧度KIN与固有断裂韧度KIC、临界距离L以及切槽半径ρ的理论关系,提出确定KIC与L的新途径。采用离散元数值方法,通过构建不同矿物晶粒粒径、不同非均质性的岩石晶粒离散元模型,开展含U型切槽岩石梁的三点弯曲数值模拟实验,结合理论分析结果,获得岩石表征断裂韧度、固有断裂韧度与临界距离;分析矿物晶粒尺寸与非均质性对岩石断裂韧度与临界距离的影响规律。研究结果表明:通过数值实验直接测定的岩石断裂韧度、临界距离值与理论求解得到的结果相符,数值实验具有较高的可靠性。细观组构特征对岩石的断裂特性具有显著影响,随着矿物晶粒尺寸增大,岩石的断裂韧度KIC逐渐减小,临界距离L逐渐增大;随着岩石非均质性的增大,断裂韧度KIC与临界距离L逐渐减小。

In order to reveal the influence of microstructural features on the fracture characteristics of rock beams with a U-shaped notch,the theoretical relationships of the rock apparent fracture toughness KIN with the inherent fracture toughness KIC,the critical distance L,as well as the notch radiusrwere established based on the theory of critical distance.A new approach to calculate KIC and L was proposed.Then,the discrete element method was used to built two groups of rock grain-based models,one of which is different in grain size,and another group is different in heterogeneity.Both of them were employed to conduct three-points bending simulation test to obtain the fracture mechanical parameters of KIN,KIC and L.Furthermore,the influences of the grain size and heterogeneity of rock on KIC and L were studied.The results show that,the obtained KIC and L from numerical tests have a good agreement with the values calculated by the theoretical equation,which indicates that the numerical experiment is highly reliable.The microstructural features have a significant influence on the rock fracture characteristics.With the increase of grain size,the rock fracture toughness KIC gradually decrease,while the critical distance L gradually increase.Additionally,KIC and L are both decreased with the increasing of rock heterogeneity.