Estimation of fracture frequency on the basis of Rock Quality Designation

Sasao, Eiji   

Science Council of Japan mentioned importance of establishment of technology to search rock body with minor fractures. It is significant to understand the fracture frequency in many rock bodies in Japan. The data widely obtained such as by borehole investigation should be available to characterise the fracture frequency. In this study, the speaker discussed the relationship between RQD (Rock Quality Designation) and fracture frequency focused on the Toki granite, central Japan. Fracture data were obtained by investigations in the boreholes drilled from the ground surface and the underground research galleries. There is a significant correlation between RQD value and fracture frequency. The data are then divided into 100 meters length and those RQD values are compared with fracture frequency. The RQD value is also associated with fracture frequency. This result indicates that the method proposed in this study can be ubiquitously applied to various lengths of borehole.