Experimental Measurement of P-wave Attenuation Due to Fractures Over the 100 to 300 kHz Bandwidth

A series of experiments was conducted where rock core specimens were cyclically loaded to 50 MPa uniaxial stress while P waveforms were pulsed along the core axis. Some of these specimens were intact while others were prepared with a single through-going tensile fracture oriented perpendicular to the core axis. Recorded data was processed to determine Q, velocity and fracture closure. Results indicated that Q was constant over the studied bandwidth and Q for the fractured specimens decreased relative to the intact specimens as fracture stress decreased. Observed variations in static fracture stiffness among the tested specimens did not result in corresponding variations in Q. Velocity results showed similar trends. This work was done to provide comparative data for related field studies examining the feasibility of using attenuation measurements in comparable frequency bands to indicate the potential for roof failure during excavation in fractured rock masses.