Abstract: The velocity of acoustic wave propagation is closely related with rock mass strength and deformation characteristics. Uniaxial compressive strength tests, uniaxial compression tests and sound velocity test were conducted on 169 red mudstone samples from the red-layer region in Chongqing. Relationships between uniaxial compressive strength R, elastic modulus E_e and wave velocity V_P are established by different functional relationships. Comparative analysis results show that their relationship expressed using second-order polynomial is the best. The empirical relationship between R and V_p could be expressed by R=4.7×10^-6×V²_P-0.023 4V_P+33.771, and the relationship between E_e and V_p is E_e=0.003 7×V²_P-19.312V²_P+27 333. The rock mechanics parameters of an engineering example were calculated and analyzed by using the established relationships. It was found that the recommended value of uniaxial compressive strength of the example is 5-6 MPa, and the elastic modulus is 2 000-3 000 MPa.

Key words: red mudstone, acoustic velocity, uniaxial compression strength, elastic modulus, second-order polynomial