A multi-frequency ultrasonic amplitude attenuation method for identifying damage of rock

High-temperature damage in rocks significantly affects ultrasonic amplitude attenuation. Inverting rock damage through amplitude attenuation offers a rapid, non-destructive, and convenient detection method. However, the single-frequency ultrasonic testing method, due to its single amplitude attenuation parameter and relatively large experimental error, is difficult to fully reflect the material’s characteristics, ultrasonic flaw detection methods based on multi-frequency amplitude attenuation are relatively scarce. To address this, the study proposes a multi-frequency ultrasonic amplitude attenuation detection method, eliminating single-frequency measurement errors and accurately characterizing the attenuation behavior of thermally damaged rocks. Experimental results show that after high-temperature treatment, P-wave amplitude attenuation increases progressively with frequency (by 50%), whereas S-wave attenuation first decreases and then rises. A correlation model between amplitude attenuation and damage variables was established, confirming that P-wave attenuation effectively quantifies rock damage. The study initially explored the interaction mechanism between multi-frequency ultrasonic and fractures: low-frequency waves exhibit increased attenuation due to boundary reflections, while high-frequency waves show enhanced attenuation as diffraction effects weaken. These findings bridge a critical gap in multi-frequency amplitude attenuation research and provide a scientific basis for identifying high-temperature damage in rocks. P-wave amplitude attenuation law can effectively characterize the damage of rocks. A multi-frequency amplitude attenuation method for identifying high-temperature damage of rock is proposed. Numerical analysis reveals the amplitude attenuation mechanism.