Effect of Frequency on Liquefaction Potential of Saturated Monterey No. O Sand

Abstract

Both stress-controlled and strain-controlled cyclic triaxial tests were conducted on samples of Monterey No. 0 sand of 30 percent relative density to assess the frequency effect on its liquefaction potential. The result indicated that the liquefaction potential of a loose sand was affected significantly in the stress-controlled cyclic triaxial test with stress reversal and the cyclic triaxial extension test when the frequency is greater than 0.01 Hz. The effect increases with the frequency. In a low frequency cyclic triaxial test, a sample was allowed to undergo severe contraction in the extension phase of the test. As a result, the sample was substantially weakened due to the generation of a large excess pore water pressure. Thus, the extension phase of a stress-controlled cyclic triaxial test was found to be more damaging and responsible for the strength reduction and liquefaction of a loose sand than the compression phase. As the frequency increases from one-hundredth of a hertz, the amount of damage per cycle of loading reduces, and the number of cycles required to cause liquefaction also increases. In a strain-controlled cyclic triaxial test, however, the above effect was found to be negligible.