Prediction of fracture frequency and RQD for the fractured rock mass using drilling logging data

摘要

Fractures in rock mass provide the dominant role in its mechanical properties. In this paper, an in situ experiment is carried out to investigate the specific energy of rock mass, from which the response of the specific energy on the open and in-filled fractures is analysed. The effect of the intact core and the open and in-filled fractures on the specific energy is studied, presenting the link between the fracture frequency and the specific energy. The result shows that the relationship between the fracture frequency and the specific energy is proposed for evaluating the fracture frequency and rock quality designation (RQD). A standard deviation of 0.18 for the specific energy can be used as a critical point to distinguish between the segment of the intact core and the fracture segment. A new prediction method is proposed to determinate the fracture frequency and RQD of rock mass, and its utilization for RQD prediction can overcome the limitations of the original RQD. This method is applied in the water conservancy project and demonstrated to be reliable and accurate by comparative studies with previous work, thus providing a low-cost and simple approach for rock quality evaluation.