Fracture toughness analysis on cracked ring disks of anisotropic rock

Summary  This paper presents a combination of the Boundary Element Method (BEM) and the cracked ring test to determine the mixed-mode (I–II) fracture toughness of anisotropic rocks. The proposed BEM is used to accurately calculate the Stress Intensity Factors (SIFs) of a cracked anisotropic plate. An anisotropic Hualien marble of Taiwan with a distinct foliation was selected to conduct the cracked ring tests. Based on the measurement of the failure load during the test, the mixed-mode (I–II) fracture toughness can be determined. Experimental results show that the radius ratio, inclination and crack angle significantly affect the fracture toughness. The mode-I fracture toughness (K _IC ) is shown to decrease with the increase in hole diameter, whereas the mode-II fracture toughness (K _IIC ) increases with the increase in hole diameter when the crack angle β is equal to 0°. The experimental methods proposed have the advantage that the material is easily prepared, the test procedure is simple, and the cost is low. Correspondence: Chia-Hau Chen, Chao-Shi Chen, Department of Resources Engineering, National Cheng Kung University, 701 Tainan, Taiwan