Abstract: Dynamic elastic modulus and damping ratio are two of the most important parameters in soil dynamic analysis. In this paper, we studied the methods of multi-stage test on remolded clay with varying confining pressure and consolidation ratio by using dynamic triaxial instrument. In consideration of pre-consolidation pressure, we put forward two test methods and obtained the dynamic elastic modulus and damping ratio and then compared them with those from conventional method. We found that the dynamic elastic modulus and damping ratio obtained by method 1 differed slightly from those by conventional method, while the dynamic elastic modulus by method 2 was larger than that by conventional method. Therefore method 1 could effectively save the number of samples compared with conventional method. Furthermore, we analyzed the influence of vibration frequency on the dynamic elastic modulus based on the theory of viscous element, and obtained the effect of frequency on the dynamic characteristics of clay through the tests. Finally, we studied a multi-stage frequency test method on one single sample and propose that the dynamic load test with large frequency has little effect on the subsequent test with small frequency; but the dynamic load test with small frequency would have impact on the following test with large frequency, resulting in attenuation of dynamic elastic modulus and decrease in maximum damping ratio. The results of multi-stage frequency test following the sequence of large frequency and then small frequency are consistent with those of conventional test. The research results are helpful to improving the soil dynamic test technology and have positive effect on dynamic characteristics research.

Key words: dynamic triaxial test, multi-stage loading, remolded clay, dynamic elastic modulus, damping ratio, vibration frequency