Abstract: Based on the theory of correlation function, a new method for calculating the dynamic modulus and damping ratio of dynamic triaxial test is proposed. Based on viscoelastic constitutive model, the amplitudes of strain and stress can be captured by analyzing the autocorrelative function of strain and stress variations with time, respectively. Thus, the dynamic modulus can be calculated. The damping ratio is determined through the characterization of the phase lag between the strain and stress time-histories which can be captured by the cross-correlation function. A series of undrained multistage strain-controlled cyclic triaxial test was conducted on saturated coral sand, Nanjing fine sand, and a type of undisturbed silty clay. The dynamic modulus and damping ratios were calculated from the experimental results using both the correlation function (CF) method and the conventional hysteresis loop (HL) method. The results show that the CF method is applicable for the calculation of dynamic modulus and damping ratio of different types of soils. The results show that the precision of the CF method for the modulus and damping ratio is significantly higher than that of the HL method within the strain amplitude of 1×10?4. When the strain amplitude is greater than 1×10?3, because of the strong nonlinearity of soil as well as the asymmetry of the stress-strain hysteresis loop, the damping ratio of soil calculated by the CF method is more reliable.

Key words: dynamic modulus, damping ratio, dynamic triaxial test, correlation function method, hysteresis loop method