Liquefied soil contains fine particles; this was discovered by researchers after the 1976 Tangshan Earthquake in China and confirmed after several subsequent earthquakes including the 1989 Loma-Prieta earthquake in California. In 1995, after Japan’s Great Hanshin earthquake, scientists discovered that sand and gravel of various sizes were contained in the liquefied foundation in addition to fine particles. Since that time, there have been many studies on the effects that fine-grained soils and different particle sizes have on post-liquefaction residual shear strength. Most have shown that shear strength is influenced by sand and particles’ physical properties.
A new paper in the Journal of Geotechnical and Geoenvironmental Engineering explores the relationship further by looking at the different physical properties and the steady-state strength. Researchers Zhaocheng Wang and Mitsutoshi Yoshimine performed undrained triaxial compression tests on sands with different physical properties. Using relative density, equivalent granular void ratio, and equivalent granular relative density, they created a unique steady-state line. The authors selected two types of silica sand and then combined those in different percentages of fines contents to test the undrained shear strength of the sand. The paper, “Effect of the Physical Characteristics of Sands on the Undrained Shear Behavior in the Steady State,” provides a means of predicting the steady-state strength for different physical properties of sand. Learn more about this research at https://doi.org/10.1061/JGGEFK.GTENG-10620. The abstract is below.
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.
Explore the new way to predict sands’ strengths in the ASCE Library: https://doi.org/10.1061/JGGEFK.GTENG-10620.