Experimental measurement and analysis of seismic wave dispersion and attenuation parameters in coal and rock under low-frequency conditions

Wave velocity dispersion and energy attenuation are key parameters for precise coal exploration and development. Low-frequency stress-strain testing provides a strategy for realizing cross-band measurements, such as seismic bands. This study implemented a series of optimization to address the challenges of high signal-noise interference and high testing accuracy requirement in such test systems. Using four coal samples from Shenfu and Linxing areas, we measured and analyzed the dispersion and attenuation characteristics of coal rock seismic waves in the low-frequency band (4-1000 Hz) under varying temperatures and confining pressures. Experimental data were interpreted using the Chapman model to discuss the factors influencing these characteristics. Results show that: ① System performance was significantly enhanced by employing the Finite Impulse Response(FIR) bandpass filter and Fast Fourier Transform(FFT), which improved signal-to-noise ratio and the accuracy of phase difference extraction. ② The elastic parameters of coal rock increased nonlinearly with confining pressure. Both P- and S-wave velocities rose with increasing confining pressure, but decreased slightly with rising temperature. The attenuation peak decreased with higher confining pressure, and increased with temperature, while the eigenfrequency remained unchanged. The Chapman model shows a good fit with the measured data, confirming its applicability. ③ The attenuation peak was positively correlated with the porosity and water saturation of coal rock, with porosity exerting a more significant influence. Variations in fluid viscosity, permeability and water saturation were related to relaxation time, which is the main cause of dispersion and attenuation eigenfrequency.