Laboratory Investigation on Rate-Dependent Properties of Sand Undergoing Low Confining Effective Stress

Abstract

Experiences of past earthquakes show that many structural damages occur due to liquefaction-induced ground deformation. Accordingly, the prediction of liquefaction-induced ground deformation plays a major role in mitigation of damages. Even though numerical methods are developed in three-dimensional way to predict liquefaction-induced deformation, lack of understanding of mechanical properties of liquefied sand makes the prediction unrealistic. Therefore, employing a hollow cylinder torsion shear apparatus, the present study aims to investigate the large deformation of liquefied sand which is tentatively considered to be rate-dependent.Since it is impossible to run experiments on specimens with null effective stress, tests were conducted at very low effective stresses such as 5, 10, and 15 kPa and possibility for extrapolation of data to zero effective stress was attempted in order to study mechanical properties of liquefied sand. In this study, specimens with low effective stress were further sheared by stepwise monotonic axial compression in drained manner and the shear stress was found to be composed of frictional as well as rate-dependent viscous components. The results suggested that viscosity of sand increases with the increase of the mean effective stress. Note that a triaxial extension test and two tests on a special light grain material (Styrofoam) were conducted to investigate viscosity at low effective stress such as 3 to 4 kPa. Noteworthy was that effects of relative density on viscosity were not significant. The test conducted with pore water, pore air, and vacuum revealed that viscosity of liquefied sand was contributed by pore fluid and particle collision during flow. Furthermore, it was suggested that increase in the fines content leads to lower viscosity.

CFD-Based Framework for Analysis of Soil–Pipeline Interaction in Reconsolidating Liquefied Sand

“…with increase in only). Although no specific calibration of was attempted, the tentative value in Table 3 is of the same order of magnitude as suggested by Gallage et al (2005)'s data (Figure 1a).…”

“…to describe the dependence of and on when < 1 (Nishimura et al, 2002;Gallage et al, 2005;Towhata et al, 2010;Guoxing et al, 2016;Chen et al, 2013Chen et al, , 2014Lirer and Mele, 2019) is the ratio between current pore pressure and pre-liquefaction effective mean stress 0 . Particularly meaningful is the work of Gallage et al (2005), who inferred Bingham properties by subjecting sand specimens at low to steps of axial compression at constant pore pressure. pronounced viscous behaviour at very low , which corroborates the assumption of fluid-like sand behaviour also in the early post-liquefaction phase.…”

“…Small increments in produce remarkable increase in and , especially when compared to values extrapolated for = 0 ( = 1). All the tests performed byGallage et al (2005) show…”

On the rheological characterisation of liquefied sands through the dam‐breaking test

“…Several non‐Newtonian formulations are available in the literature, among which the Bingham model has gained over the years the widest popularity for applications involving liquefied sands. () The popularity of the Bingham model does not only arise from its simplicity, but also from the existing bulk of experimental data in its support—as shown by O'Brien and Julien for fine‐grained materials, and Nishimura et al and by Gallage et al for liquefied sands.…”

Geotechnics and Earthquake Geotechnics Towards Global Sustainability

“…Moreover, the frictional (inviscid) component of stress was subtracted from the measured axial stress and the viscous stress component was calculated; for its detailed procedure, refer to Gallage et al (2005). The number of successful freefall tests was only two and the generated rate of axial strain was 1%/s in both of them.…”