Shear wave velocity-based new procedure for assessing seismic liquefaction triggering of sand-gravel soils

The shear wave velocity V_s is one of the most basic parameters for characterizing the dynamic behaviours of soils, and it is also an index for assessing the seismic liquefaction resistance of sand-gravel soils. To explore the influences of gravel content G_c, relative density D_r, and initial effective confining pressure ${\sigma '_0}$ on V_s, a series of bending element tests are carried out on angular and subround sand-gravel mixtures with varying G_c, D_r, and ${\sigma '_0}$. The results indicate that V_s has a trend of first increasing and then decreasing with G_c. Under the assumption that the size limit for the fillers is 0.1 mm, it is found that a virtually unique correlation of negative power function exists between the binary packing material-based skeleton void ratio e_gk and the normalized shear wave velocity V_s/(${\sigma '_0}{\text{/}}{p_{\text{a}}}$)ⁿ, in which n is a power function of the coefficient of uniformity C_u of sand-gravel mixtures, and ${p_{\text{a}}}$ = 100 kPa. On this basis, an empirical formula for V_s and e_gk is proposed. Based on the cyclic laboratory test data on the cyclic resistance ratio (CRR_15-lab) in 15 cycles of various sand-gravel mixtures published in the literatures, a shear wave velocity-based equation for assessing the liquefaction triggering of sand-gravel mixtures is proposed. It is validated by the liquefaction data of sand-gravel soil sites during the 2008 Wenchuan great earthquake, China, and the 1976 Friuli earthquake, Italy. The new procedure for assessing the liquefaction triggering of sand-gravel soils is valuable in engineering practices.