Estimation of the Compressive Strength of Intact Rock Using Non-Destructive Testing Method Based on Total Sound-Signal Energy

This study proposes a new non-destructive testing (NDT) method to assess the compressive strength of intact rock. The method is based on total sound-signal energy, which is calculated using the sound signal generated from impacting intact rock. A device was developed to generate an impact sound from a test object using a rotating free-falling impact ball and subsequent repetitive impacts from the rebound action. To validate the method, soil cement, cement paste, pine wood, shale, and granite specimens were first tested to determine the correlation between the direct compressive strength and the total sound-signal energy. Next, the method was applied to a number of shale and granite specimens. The results show a direct relationship between the direct compressive strength and the total sound-signal energy. Correlation equations between the total sound-signal energy and the direct compressive strength were determined for the different rock types, both separately and together through regression analysis. Then, the determined correlation equations were used to estimate the strength of intact rock and validate the method. Statistical analysis indicated that the estimated compressive strength was quite reliable for both rock types. It is expected that the new NDT test method could play a meaningful role in non-destructively estimating the compressive strength of intact rock in the future.