Based on the modified Biot theory

the effects of grain compressibility

frequency

porosity

fluid viscosity and dynamic permeability on the velocity and attenuation of the three bulk waves (P1

P2

S) in infinite two-phase porous media are studied by numerical calculation

respectively. Numerical results show that: (1) the velocity and attenuation of compressional waves (P1

P2) are variable and approximately linear with grain compressibility

while those of shear wave (S) almost keep constant

and by quantitative comparison

it is found that whether the effect of grain compressibility can be neglected or not depends on the ratio between skeleton bulk modulus and grain bulk modulus . (2) The porosity affects the velocity of P1 and S obviously; and it can be predicted that mutual conversion between P1 and P2 when the porosity almost reaches 1.0. (3) Both the fluid viscosity and the dynamic permeability have effects on the velocity and attenuation of P1

P2 and S

but for each of the waves

the variation trends with those two parameters are almost opposite. (4) The velocity and attenuation of the three bulk waves increase with frequency; and among them P2 is affected by frequency most.