Effects of initial static shear stress orientation on cyclic behavior of calcareous sand

Abstract

The current study investigated the effect of the initial static shear stress orientation on the liquefaction behavior of Hormuz Island calcareous sand. An experimental study was performed using nine monotonic and 43 cyclic undrained bidirectional simple shear tests. The experiments were conducted on loose and dense samples having different cyclic shear ratios and initial static shear ratios (α) at two orientations. It was found that, as the value of α increased, the shear behavior and failure mechanisms changed. The results showed that calcareous sand responded differently to changes in α and in the symmetrical tests (α = 0) showed higher resistance to liquefaction than siliceous sand. Contrary to siliceous sand, as α increased to 0.1, the value of Kα increased to greater than 1 for loose Hormuz sand specimens. Moreover, an increase in α from 0.1 to 0.3 caused a slight increase (less than 10%) in the Kα value for dense specimens. It was also observed that liquefaction resistance in the perpendicular loading mode was higher than in the parallel mode under the same conditions. It would appear that reversal of shear stress plays an important role in cyclic resistance and behavior in the parallel and perpendicular loading modes. A model is proposed to predict liquefaction resistance for calcareous sand in the presence of α.