시추코어를 이용한 암석의 mode II 파괴인성 시험법 개발과 적용

Rock fracture mechanics has been widely applied to various fields of rock and civil engineering. But most researches covered mode Ⅰ behavior, though mode Ⅱ behavior is dominant in rock engineering. Until now, there is only one ISRM suggested method for mode Ⅱ toughness of rock. A new SCC (Short Core in Compression) mode Ⅱ toughness test method was developed considering 1) application of confining pressure, 2) easiness of notch creation, 3) utilization of existing equipment, 4) simple test procedure. The stress intensity factors were determined by 3D finite element method considering line and distributed loading conditions. The tests with granite specimens were carried out using MTS 815 rock test system with a loading rate of 0.002 ㎜/s. The mean value of mode Ⅱ fracture toughness of granite showed 2.33 ㎫√m. Mode Ⅰ toughness of the same granite was 1.12 ㎫√m, determined by Brazilian disk test and K IIC /K IC = 2.08. The smooth fracture surface with rock powder formation also supported mode II behavior of SCC method. The SCC method can be used for the determination of mode Ⅱ fracture toughness of rocks based on the current results.