Stress can have a significant effect on the stability of pillars. To get an
accurate picture of pillar stability, information is needed not only on the
initial stress magnitude and distribution but also on all subsequent stress
changes.
Sonic methods have the potential to be among the fastest, most economical and least destructive means of stress measurement. Wave
propagation velocity has long been applied to the investigation of the upper
mantle and crust stress. Recently, it has also been applied to rock burst
prediction and mine site investigations. Another parameter for investigating
stress in rocks is the attenuation coefficient. Attenuation has been observed
to be more sensitive to stress changes than wave velocity; however, the
measurement of attenuation is more difficult than that of wave velocity.
In this study, the mechanism of sonic attenuation in rock is reviewed.
Both the velocity and the attenuation of sound waves in five different rock
types under various stress levels were examined in the laboratory. It was
found that the relationship between the velocity ratio and stress and that
between the attenuation ratio and stress, for a specific rock type, can be
expressed by simplified second order polynomial equations.
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