The development of engineering rock classification systems has received considerable attention during the past few years. The purpose, application and method of assigning an index of rock quality, vary considerably between these systems. Several of them are directed toward the assessment of stability and support potential of an excavation whereas other systems are estimating a particular response of the rock, i.e. blastability or ripability. In the most widely accepted engineering rock classification systems, rock quality is expressed either in terms of meaningful descriptions or by a quantitative evaluation of a geomechanical property or properties. The application of sonic wave parameters in the engineering classification of rock mass and rock material has been the subject of considerable interest amongst investigators. The advantages of utilizing such techniques include minimal sample preparation, capabilities for large scale testing and the ability to perform non- destructive as well as reproducible tests. The purpose of the research presented in this paper was to determine the most appropriate sonic wave parameters for engineering rock classification purposes, to utilize these findings in developing new or modifying existing classification systems and, finally, to apply this information in the prediction and analysis of blasting wave characteristics.
An engineering classification system requires the definition and evaluation of the selected rock criteria by laboratory or field testing. Laboratory work on intact rock usually consists of the measurement of the modulus of elasticity and the unconfined compressive strength. Field investigations may include the determination of the in-situ modulus of deformation and the spacing and characteristics of the discontinuities. The measurement of such parameters requires sample collection and preparation, field preparation, extensive field work and, in many cases, considerable experimental instrumentation. The estimation or approximation of the above properties and rock quality characteristics from parameters determined from sonic wave testing, such as the velocity, amplitude and frequency of P- and S-waves, has considerable merit. If such correlation could be established, existing engineering rock classification systems may be modified and new systems can be developed utilizing sonic parameters. The mathematical equations describing sonic wave propagation through elastic or viscoelastic media have been well reported in the literature (Roussel, 1968; Stagg and Zienkiewicz, 1968; Desai and Christian, 1977). In this context, the term sonic wave refers to any mode or frequency of particle oscillation that propagates through solid medium. In the case of an elastic medium, expressions are available relating elastic the following theoretical properties with sonic wave parameters: (mathematical equation) (available in full paper)