Energy-Based Assessment of Liquefaction Resistance of Rooted Soil

Plant roots have been shown to improve the soil resistance to liquefaction upon cyclic loading. However, the effect of roots and their orientations on any changes in soil anisotropy and the mechanisms of dissipated energy involved at liquefaction state are not clear. This study applied the energy-based method to evaluate the liquefaction behavior of rooted soils of varying root volume ratios (RVRs). Results of 12 undrained cyclic triaxial tests on rooted soils published in the literature were reinterpreted under this energy framework. The assessment showed that the normalized cumulative dissipated energy ($\sum \mathrm{\Delta }W/{\sigma }_c^{\prime }$, where ${\sigma }_c^{\prime }$ is the effective confining pressure) of rooted soil at liquefaction state can be related to the cyclic resistance ratio at 15 cycles (${\mathrm{CRR}}_{15}$). It was discovered that roots that were predominantly orientated in the direction perpendicular to the major principal stress of extension path reduced soil anisotropy. Additionally, the $\sum \mathrm{\Delta }W/{\sigma }_c^{\prime }$ was linearly correlated with the normalized cumulative strain energy ($\sum 4W/{\sigma }_c^{\prime }$) with a gradient of approximately 2, which implies that any recycling and recovering of strain energy was minimal in rooted soils.