Fractal wave velocity evolution model of ultrasonic propagation and attenuation in water-bearing coal

Abstract

A fractal wave velocity evolution model of the water-bearing coal is constructed to explore the relationship between the complex pore and fissure structure parameters of the water-bearing coal mass and the ultrasonic P-wave velocity, based on the fractal theory and with consideration of the attenuation of ultrasonic waves propagating in the porous media of coal. In addition, experimental study and numerical analysis of the model are carried out, the following conclusions are reached. (1) The P-wave velocity increases with the increase of the coal sample length, the water content, the wave velocity in the coal matrix and the maximum pore radius, and decreases with the increase of the minimum pore radius. (2) The experimental results also show that the P-wave velocity increases with the increase of the water content and fractal dimension of the coal sample, indicating that the wave velocity prediction model has high accuracy. (3) The fractal dimension, water content, wave velocity in the coal matrix and coal sample length have great effects on the P-wave velocity of coal samples, while the minimum pore radius and the maximum pore radius have relatively little influences on the P-wave velocity.