Experimental investigation of the effect of relative densities and type of loading on sand liquefaction under irregular earthquake loading

The cyclic triaxial test has been widely used to evaluate the liquefaction potential of soil over the past few decades. When a specimen is subjected to repeated shear loading, the sand particles tend to rearrange their stacking into a denser state. While drainage is prevented, the generation of pore pressure and loss of effective stress have resulted. This paper presents a systematic experimental investigation into liquefaction behavior of saturated sand subject to seismic loading with various relative densities such as 30, 50 and 70 percent. Dynamic triaxial tests were run on saturated firozkooh sand using irregular time history loads that recorded during the 1999 Chi-Chi earthquake in Taiwan. The records could be classified as shock and vibration type waveforms. The effect of each type of waveforms and relative densities of sand samples on liquefaction potential of sand was evaluated also in order to compare these results with previous studies, some cyclic tests have been done with various relative densities 30, 50 and 70 percent. The triaxial test results indicate that the pore pressure generation and liquefaction resistance of sand are influenced by the relative densities and the type of irregular loadings. Also with the increasing duration of the records in the same PGA, the vibration waveform have more liquefaction potential than shock waveform.