Experimental study on the effect of cyclic preloading on the resistance to liquefaction of saturated loose sand under wave loading

Abstract

By using the soil static and dynamic universal triaxial and torsional shear apparatus, a series of combined cyclic shear tests are performed to simulate the rotation in the principal stress direction induced by ocean wave. The tests include the cyclic preloading tests and liquefaction tests in the second loading on saturated loose sand with a relative density of 30%. The all tests are consolidated under isotropic condition. The effect of the cyclic preloading on the resistance to liquefaction of saturated loose sands under the condition of continuous rotation in the principal stress direction is investigated. Experimental data indicate that the void ratio of saturated sands has a negligible reduction after cyclic preloading. With the increase of the intensity of cyclic preloading (in the amplitude and in the number of cycles), the resistance to liquefaction in the second loading is increased continuously under the condition that the liquefaction does not occur during the cyclic preloading. The reason is that the construction of more stable structure due to the uniformity of the void and the better interlocking of the particles when the cyclic preloading is applied to the saturated sand.

Effect of shaking strength on the seismic response of liquefiable level ground

“…To a greater extent, it is attributed to the formation of a more stable structure of soil particles during the small vibration in Test A. The experimental results of the triaxial and torsional shear tests conducted by Zhang et al (2009) andWichtmann et al (2005) also showed that the cyclic preloading of small amplitudes causes a negligible reduction in the void ratio, but improves significantly the liquefaction resistance of sand. These results were attributed to the fabric change of soil resulting from the uniformity of the void ratio and better interlocking of particles during cyclic preloading.…”

“…However, as pointed out by Finn et al (1970), preshearing influences the liquefaction resistance of saturated sand according to triaxial and simple shear cyclic loading tests. The experimental studies by Zhang et al (2009) and Wichtmann et al (2005) also indicated that the cyclic preloading could improve the liquefaction resistance of sand under the condition that liquefaction does not occur during the cyclic preloading. Therefore, the effect of shaking history on seismic ground response cannot be ignored.…”