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The standard of practice when assessing the seismic performance of well graded sands, is to assume the response is similar to poorly graded clean sands, which comprise the majority of the liquefaction case history database. Using the 9-m radius centrifuge at UC Davis, an experiment was designed to elucidate the system-level liquefaction triggering response for a poorly graded and well graded sand. The experiment consisted of two identical 10-degree slopes positioned side-by-side in the same model container, with one slope constructed with a well graded sand and the other with a poorly graded sand. The D10 grain size was the similar for both gradations and therefore the permeability was comparable. The slopes were dry pluviated to the same relative density of Dr=63%, while the absolute densities were different. The dynamic response of both slopes was similar up until liquefaction triggering, with both sands reaching excess pore pressure ratios close to unity within 1-2 cycles of loading. Following the onset of liquefaction, the well graded sand exhibited strong dilative tendencies and embankment deformations attenuated rapidly during successive loading cycles, while the poorly graded sand embankment continued to deform. This study demonstrates that the posttriggering response of well graded and poorly graded sands differ due to their different absolute densities and dilatancies for the same relative density. It is expected that findings from this research will lead to a more rational accounting of gradation properties in the evaluation of and design for liquefaction effects, as well as the interpretation of case histories.