A simple method for determining independent fracture toughness and tensile strength of rock

• Published in: International journal of mining science and technology Vol. 32; no. 4; pp. 707 - 726
• Main Authors: Guan, Junfeng, Zhang, Yulong, Meng, Jiangfeng, Yao, Xianhua, Li, Lielie, He, Shuanghua
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.07.2022; Elsevier
• Subjects: Boundary effect; Fracture toughness; Rock; Size effect; Structural geometry parameter; Tensile strength; Structural geometry parameter; Rock; Boundary effect; Tensile strength; Size effect; Fracture toughness
• ISSN: 2095-2686
• DOI: 10.1016/j.ijmst.2022.05.004

This paper develops a model that only requires two sets of small-size rock specimens with the ratio of the structural geometry parameter maximum to minimum ae,max:ae,min ≥ 3:1 to determine the rock fracture and strength parameters without size effect and predict the actual structural performance of rock. Regardless of three-point-bending, four-point-bending, or a combination of the above two specimen types, fracture toughness KIC and tensile strength ft of rock were determined using only two sets of specimens with ae,max:ae,min ≥ 3:1. The values KIC and ft were consistent with those determined using multiple sets of specimens. The full structural failure curve constructed by two sets of small-size specimens with ae,max:ae,min ≥ 3:1 can accurately predict large-size specimens fracture failure, and ±10% upper and lower limits of the curve can encompass the test results of large-size specimens. The peak load prediction curve was constructed by two sets of specimens with ae,max:ae,min ≥ 3:1, and ±15% upper and lower limits of the peak load prediction curve can cover the small-size specimen tests data. The model and method proposed in this paper require only two sets of small-size specimens, and their selection is unaffected by the specimen type, geometry, and initial crack length.