Effects of Mica Content on Cyclic Resistance of Poorly-Graded Sand

In California several geotechnical projects located in seismically active areas have encountered recent alluvial deposits with varying mica contents. Post-construction liquefaction susceptibility evaluations can be made, however case histories do not exist for soils with considerable mica contents, so it is difficult to evaluate if the results from the post-construction investigation are accurate. Cyclic triaxial tests on isotropically consolidated specimens were performed to evaluate the effect of mica content on the liquefaction of poorly-graded sand. The results show that fewer cycles are required to initiate liquefaction for specimens with higher mica contents. It should be noted that the impact of mica particles on the maximum and minimum void ratio suggests that the maximum compacted density of mica-sand mixtures decreases with an increase in mica content. Therefore, if relative density is used as an indicator of liquefaction potential for sands with varying mica contents, than a correction factor should be applied to the in-situ field tests, such as SPT blow counts or CPT tip resistance and sleeve friction values.