ABSTRACT
Efforts to relate rock quality and seismic velocity have been made at intervals, during the development and integration of rock engineering and engineering geology. Included in this review will be RQD, joint or fracture frequency (Fm1), and the Q-value (the ‘static’ rock mass quality rating). Their various relationships to P-wave velocities obtained from shallow refraction seismic, and also from down-hole sonic logging, will be explored. The correlations obtained have had emphasis on hard rocks, with or without weathering, without the complication of matrix porosity variations, or large ranges of strength and density. These preliminary empirical correlations between RQD and velocity ratio, and between Fm1 or the Q-value and Vp, must necessarily include the effect of depth or stress level on Vp, for them to be more widely applied. On the basis of numerous reviews of deeper seismic measurements, a method is developed in this chapter, that includes matrix porosity and rock strength besides all the rock mass attributes of jointing, faulting, weathering and clay. To these are added the all important influence of depth or stress level, causing gradual or rapid closure of many or all of the joint sets.
