Effects of Low-Number Previbration Cycles on Dynamic Properties of Dry Sand

Abstract

This study presents direct evidence for the influence of the previbration cycles induced in the conventional resonant column tests on the measured dynamic properties of a dry sand. The tests were performed on an energy-injecting virtual-mass resonant column system, under which the material properties can be measured at a very low number of previbration cycles (<20). The test results show that for the sand tested at strain amplitudes beyond the elastic threshold, the influence of previbration is moderate on modulus but very significant on damping, particularly in the low range of the numbers of vibration cycles (<500). This observation is consistent with findings in the literature, which are based on combinations of static and dynamic test data. The effects of the low number of vibration cycles on the normalized modulus reduction and damping curves have also been examined. The results show that the modulus reduction curves are not significantly affected by these previbration cycles, whereas the damping curves in the range exceeding the elastic threshold are.