Couple Effect of Loading Frequency and Uniformity Coefficient on the Liquefaction Resistance of Sand

The uniformity coefficient (Cu) of sand and the cyclic loading frequency (f) is unclear in affecting soil's cyclic undrained behavior. This note presents experimental research on the combined effect of f and Cu on the liquefaction resistance of the sand. A series of constant-volume, stress-controlled, cyclic direct simple shear tests (CDSS) were performed on silica sands mixed with different particle proportions to make both poorly (SP) and well-graded (SW) samples. SP and SW samples are deposited in a medium-density dry state, consolidated to vertical stress of 100 kPa, and cyclically loaded under a cyclic stress ratio of 0.1 with various loading frequency (f = 0.03, 0.05, 0.1, 0.2, and 0.5 Hz). In SP sand, the number of cycles to cause liquefaction (Ncyc) remains unchanged when the load frequency rises from 0.03 Hz to 0.1 Hz, and increases when the load frequency rises from 0.1 Hz to 0.5 Hz. It can be stated that SP sand's liquefaction resistance is affected by the high loading frequency. On the contrary, the effect of loading frequency on the Ncyc of SW sand is negligible. Furthermore, SP sand is more resistant to liquefaction than SW sand. According to this study, Cu and f should be included in the sand's liquefaction resistance analysis.