RQD Models and Fracture Spacing

Abstract

Various statistical models are proposed for estimating the quality of rock masses. These models are then employed to relate RQD with the av erage number of discontinuity or average intact lengths. It is observed that the standard deviation of the intact lengths plays an additional important role in the rock quality classification. Increase in the standard deviation improves the rock quality. The proposed models are verified with the limited amount of data that are available in the rock mechanics literature. The models as a whole cover almost all of the feasible region in the RQD versus average number of discon tinuity domain.