Innovation of fracture toughness test for new horizon of rock fracture mechanics

2014 Fiscal Year Final Research Report

• Project/Area Number: 25630416
• Research Category: Grant-in-Aid for Challenging Exploratory Research
• Allocation Type: Multi-year Fund
• Research Field: Earth system and resources engineering
• Research Institution: Kumamoto University
• Principal Investigator: OBARA Yuzo 熊本大学, 自然科学研究科, 教授 (50135315)
• Co-Investigator(Kenkyū-buntansha): ISHII Tateki 木更津工業高等専門学校, 准教授 (60400280)
• Research Collaborator: KATAOKA Minami
• Project Period (FY): 2013-04-01 – 2015-03-31
• Keywords: 岩石破壊力学 / 破壊靱性試験 / マイクロ岩石供試体 / 微視的破壊靱性 / 巨視的破壊靱性 / 有限被膜法

Outline of Final Research Achievements

A new material testing system was developed to evaluate microscopic fracture toughness of mineral grains within rock. This testing system consists of an optical microscope, stages, loading apparatus and data collection unit.The specimen used in this test was micro-sized cantilever beam type (10 × 10 × 50micro-m) with an artificial notch. The microscopic fracture toughness test was completed successfully and it is shown that the new testing system is available to evaluate microscopic fracture toughness of rocks. The experimental results show that the microscopic fracture toughness are different from each specimen. It was discussed that these microscopic properties are influenced by the mechanical weak planes such as cleavage due to crystal structures.
Furthermore, numerical fracture tests by FCM were conducted. These numerical tests simulated a conventional semi-circular bending tests. The numerical results agree with that of the experiments in machanical and facture behavior.

Free Research Field

岩盤工学