CDSS Tests for Evaluation of Vibration Frequency in Liquefaction Resistance of Silica Sand

Abstract

AbstractThe frequency of ground motions during earthquakes is typically on the order of a few hertz. In the evaluation of the liquefaction resistance of soil in laboratory tests, it is necessary to consider various vibration frequencies generated by real earthquakes. The effect of vibration frequency has been studied by cyclic triaxial tests; however, it has rarely been investigated by cyclic direct simple shear (CDSS) tests, which are more similar to the cyclic loading conditions associated with earthquakes. In this study, a series of CDSS tests was performed on relative density of 40% of sand obtained from Nakdong River. Two different initial vertical effective stresses (σ′v0, 100 and 200 kPa) and four different frequencies (f, 0.05, 0.1, 0.5, and 1 Hz) were applied to evaluate the effect of the vibration frequency on the liquefaction resistance of clean sand for both the undrained and drained conditions. For the undrained CDSS tests, the liquefaction resistance of the sand was observed to increase with f, regardless of σ′v0. The maximum increase in the cyclic resistance was 15% when f was increased from 0.1 to 1 Hz. For the drained CDSS tests, with an increase in f, the rate of volumetric strain accumulation decreased and the shear modulus ratio increased.KeywordsSand liquefactionVibration frequencyUndrained CDSS testDrained CDSS test