Abstract: P-wave propagation tests of red sandstone, marble and granite samples were carried out under dry and water-saturated condition using nonmetal sonic wave testing system to study the velocity characteristics of P-wave propagation in different rocks. Rules of wave form, wave attenuation and wave spectrum were researched using Fourier and wavelet transforms. The experimental results indicate that: (1) The longitudinal wave velocities of red sandstone, marble and granite samples under water-saturated condition are slightly higher than those under dry condition. (2) P-wave velocity of rock samples are influenced by density, porosity and hardness. (3) With the same trigger signal, the energy concentrates on the low frequency band under water-saturated condition, and focuses on the high frequency band of the same samples under dry condition. (4) The energy of acoustic wave signals of the three kinds of samples under water-saturated condition attenuates rapidly, with plump coda wave. The energy of dry samples attenuates slowly, with shriveled coda wave. (5) The distribution of interior pores and microcracks and conditions of water contents in rock are reflected by the wave velocity and wave form of acoustic signal, which are presented in time, frequency and time-frequency domain.

Key words: rock mechanics, acoustic wave, frequency spectrum, Fourier transform, wavelet transform