Effect of the Physical Characteristics of Sands on the Undrained Shear Behavior in the Steady State

The steady-state shear strength of sands is affected by the physical properties of the sand. If the correlation between physical properties of sands and their steady-state strength is known, the steady-state strength can be obtained directly without mechanical experiments. Thus, the correlation has engineering significance for the prediction of liquefaction phenomena. This study explored the relationship between different physical properties and steady-state strength by conducting undrained triaxial compression tests on sands with different mean particle sizes, particle-size ranges, and fines contents. The results show that the steady-state strength of clean sands decreases with increasing mean particle size or particle-size range. The steady-state strength of nonplastic fines mixes is lowest when the fines contents is about 30% if their densities are the same, and increases gradually thereafter with increasing fines contents. When we used relative density instead of void ratio or dry density to evaluate steady state, the effects of grain size and its range of the host sand were diminished, whereas the effect of fines contents remained. On the other hand, when equivalent granular void ratio was used, the influence of fines contents ceased but the effects of grain-size distribution remained. In order to take advantage of both relative density and equivalent void ratio, the concept of the equivalent granular relative density is proposed, which is beneficial for evaluating the steady-state of sands with different physical characteristics, including the grain size and its range of host sand and fines content. The significance of this result is that the steady-state strength of various sands can be predicted to some extent from the density and grain-size distribution of the sand as well as the maximum and minimum densities of the host sand alone.