Abstract
Quantitative evaluation of crack initiation and propagation is important for examination long-term safety of rock structure. Crack propagation criterion is done based on the concept stress intensity factor and fracture toughness of linear elastic fracture mechanics. Recently, this concept is usually applied in the rock engineering. And, fracture toughness is often assumed to be isotropy. However, it is thought that fracture toughness has directional characteristic when rock is anisotropy by influence of crack condition. There are very few reports about a direction characteristic of fracture toughness and relation with a structural feature in rock. The purpose of this study is to evaluate a direction characteristic of fracture toughness KIC in mode I, tensile or opening mode. The specimen is crystalline granite with physical orthotropic. Details of the consideration are as follows.
1) Examination for laboratory testing techniques to decide direction characteristic of KIC by SCB test i.e. semi-circular specimens under three-point bending.
2) Direction characteristic of KIC and the relevance of the structural characteristic of specimen.
3) Calculation of the maximum crack length in tensile failure.
In addition, we quantitatively verified mason's experience rule from the result of the direction characteristic of KIC.
