Fracture Toughness of Granite Measured Using Micro to Macro Scale Specimens

The objective of this study is to examineany variationfrom micro to macroscalemode-I fracture toughness of granite usingmicro-sized specimen and semi-circular specimen. The rock used in the tests is Iksan granite (Korea)which is composed ofminerals, such as plagioclaseandalkali feldspar, quartz. In order to investigate microscalefracture toughness, a mechanical testing machine was used. This machine is an original one and developedby ourselves. In the test, a micro-sized cantilever beam type specimen was used. Its dimension is 10 × 10 × 50 μm. On the other hand, in order toexamine macroscalefracture toughness, Semi-Circular Bend (SCB) test is adopted. This is one of ISRM-suggested methods for estimation of the mode-I fracture toughness of rocks. Thesemi-circular specimens are preparedwith a radius of 12.5mm to 50mm. Based on the fracture toughness obtained from both tests, the size effect of granite is discussedin the range from micro to macroscale