Assessing the liquefaction potential of a sand specimen by using resonant column test

The liquefaction potential of soils is usually assessed based on cyclic simple/triaxial/torsional shear tests. These tests are generally associated with low frequency vibrations in a range of 0.5-10 Hz which are often induced by an earthquake. There is, however, hardly any literature to assess the liquefaction potential when subjected to high frequency (20-100 Hz) and low shearing strain amplitude excitation (approximately 0.0001%-0.1%) - often associated with the foundations of different operating vibratory machines. In the present research, it is attempted to determine the liquefaction potential of a cylindrical saturated sand specimen based on resonant column (RC) tests. The effect of effective confining pressure, relative density of sand and the number of excitation cycles on the liquefaction potential has been investigated. Beyond a threshold shearing strain of 0.01%, a continuous rise in the porewater pressure was experienced when subjected to excitations which eventually lead to the liquefaction of saturated sand. The onset of liquefaction was also revealed by the Poisson ratio - which tends to become close to 0.5 as was observed from the bender and extended elements tests. The number of excitation cycles to cause initial liquefaction increases with (i) a decrease in the cyclic stress ratio, and (ii) an increase in the relative density of the sand. The present research clearly reveals that with a provision of continuous excitation in a RC apparatus, it becomes possible to assess the liquefaction potential of a specimen when subjected to high frequency low strain excitation. On account of low shearing strain in RC tests, the numbers of cycles required to cause liquefaction were found to be much greater than that reported in literature on the basis of cyclic shear tests.