Experimental study of liquefaction resistance: effect of non-plastic silt content on sand matrix

This paper highlights the effect of non-plastic fines on sand matrix by performing a series of undrained triaxial tests. The silty sand specimens were reclaimed by moist tamping method and two distinct density indexes of sand matrix were selected: I-_Dmat=0.00 (<0.15) for very loose state and I_Dmat=0.50 (>0.40) for medium-dense state. The addition of non-plastic fines to the host sand matrix makes the specimens more resistant to liquefaction by inducing dilatant behaviour and reducing the excess pore water pressure Δu. As for instability line in the very loose state (I_Dmat=0.00), a rotation is observed on the p'-q plane with increasing non-plastic fines fraction. This trend is non-linear and becomes less remarkable after a certain threshold value in fines fractions. In the medium-dense state (I_Dmat=0.50), there is no significant effect of non-plastic silt particles on the phase transformation state. Regarding the ultimate steady state, the line is unified in the p'-q space, but a clockwise rotation is observed in the log(p')-e space. Furthermore, the exponential form shows a good fitting performance for silty sand. (authors)