Previbration Signature on Dynamic Properties of Dry Sand

Abstract

The shear modulus and damping ratio of soils at low to medium strains are essential input parameters in dynamic response analysis of soils. As soil elements in the field always have a history of being subjected to vibrations due to earthquakes, construction works, and vehicle motions, etc., the previbration effect on the dynamic properties of soils needs to be addressed appropriately. This study presents a series of tests performed by a newly developed resonant column system that enables the assessment of the dynamic properties of soils that have only undergone dozens of vibration cycles to investigate the impact of the vibration history on the dynamic properties of dry sand. Both the shear modulus and damping ratio of sand under different confining pressures (p′) are measured after the application of a previbration with a wide range of vibration amplitudes (γpre) and number of cycles (N). The results show that an elastic threshold strain exists for the dynamic properties of sand, beyond which the effect of the vibration history can be identified from the shear modulus reduction and damping ratio curves. The results also confirm that the effect of the vibration history on dry sand depends on the test variables of γpre, N, and p′. In addition, a new interpretation method is proposed to quantify the combined effects of γpre and N on the signature of the vibration history, which could potentially be useful for interpreting the dynamic properties of the in situ soils that may experience previbration.

The Dynamic Properties of Sand under Torsion: A Literature Review

“…This pattern inverted when the pre-vibration increased to 0.05%, as the maximum shear modulus increased by 10% with the number of cycles (=100,000). The trend found by Yang et al [63] appears in Figure 8. Furthermore, the study shows a negligible effect of the confining pressure on the influence of pre-vibration (less than 3%).…”

“…Another study on the pre-vibration effect on the dynamic properties of dry Toyoura sand was carried out by Yang et al [63]. They improved their energy-injecting virtual mass (EIVM) resonant column system (Mark II) to reduce the time needed to reach a steady-state vibration.…”