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It is becoming increasingly important to be able to predict and reduce ground vibration and airblast so that mine operations may achieve their environmental requirements. The observed vibration and airblast at any monitoring location is influenced by variables such as the weight and type of explosive used per delay, the delay time sequence, scatter in that sequencc. the spatial pattern of blastholes and properties of the transmitting medium. The present work shows how the separate influence of these variables may be analysed using a Monte Carlo model that has a predictive power superior to that of the traditional charge weight scaling laws.Charge weight scaling laws have sometimes been observed to give acceptable predictions at a fixed monitoring location for the consistent use of a particular blast design. However, unlike the Monte Carlo model, such laws cannot be used to predict the likely changes in vibration due to any planned changes in blast design.Monte Carlo predicted contours of airbhst and vibration show that the blasthole locations and the direction of initiation have a considerable effect at any monitoring location. This is due to influences such as the finite travel time of the disturbance as well as thc screening effect. The travel time delay between blastholes is more significant for airblast since the velocity (334 m/s) of sound in air is typically 10 times lower than the speed of vibrational waves through the ground. It is also well known that previously fired blastholes may provide a screen for both airblast and Vibration produced by a current hole as it initiates. In the case of airblast, screening may occur due to thc airborne particulate matter produced by previous holes; in the case of vibration, screening may occur due to ground fractured by these previous holes.

Recordings were made of seismic pulses produced by explosive sources in rock underground at Mount Isa Mine, Queensland, Australia. Analysis of the experimental results in light of the theory of Kjartansson (1979) indicates that the simple rise time law τ = τ0 + CT/Q is inadequate for describing the attenuation of seismic pulses generated by a realistic source. The rise time law makes no allowance for the spectral characteristics of the source except by assigning a value of τ0 to each source and is an oversimplification of the process of source propagation through rocks; consequently, the constant C is source dependent. An alternative method of estimating pulse attenuation is presented, which overcomes the difficulties inherent in the rise time law.

For the same volume of rock, I compare the attenuation obtained by seismic pulse transmission over the frequency range 1–150 kHz with that obtained by vibrational resonance techniques over the frequency range 1–50 kHz. The initial studies were performed on a rectangular block of medium‐grained granite which was large enough to permit the installation of a seismic pulse transmission array over a 1.8 m path length, yet small enough to permit whole‐body resonance. A Q of 82, for the P wave, was derived from the vibrational resonance results, whereas a Q of 15 was derived from the pulse transmission results. In light of models proposed for the viscoelastic, geometric, and elastic scattering attenuation mechanisms, the experimental results suggest that this large discrepancy in Q values is due to elastic scattering by grain clusters (rather than individual grains) within the granite. Scattering is significant in the high‐frequency pulse transmission tests, but is considered insignificant in the lower frequency resonance tests. Furthermore, this scattering is represented approximately by a constant-Q loss mechanism, which makes it difficult to separate unambiguously elastic scattering and viscoelastic losses. Subsequent studies performed on a large block of fine‐grained norite yield a resonance Q of 89 and a pulse Q of approximately 102 and suggest a negligible scattering loss for this material. The experimental results for the norite imply that the constant-Q theory of seismic pulse attenuation provides a reasonable description of wave attenuation in a dry, fine‐grained crystalline rock over the frequency range 1–150 kHz.

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