Maximum shear modulus anisotropy of rooted soils

The maximum shear modulus (G 0(ij) ) of rooted soils is crucial for assessing the deformation and liquefaction potential of vegetated infrastructures under seismic loading conditions. However, no data or theory are available to account for the anisotropy of G 0(ij) of rooted soils. This study presents a new model that can predict G 0(ij) anisotropy of rooted soils by incorporating the projection of the stress tensor on two independent tensors that describe the soil fabric and root network. Bender element tests were conducted on bare and vegetated specimens under isotropic and anisotropic loading conditions. The presence of roots in the soil increased G 0(VH) at all confining pressures (p′), as well as G 0(HH) and G 0(HV) at low p′. However, the trend was reversed at higher p′ because the roots reduced the effects of confinement on G 0(ij) by replacing stronger soil–soil interfaces with weaker soil–root interfaces. Roots made the soil fabric and G 0(ij) more anisotropic. The proposed model can effectively predict the observed anisotropy of G 0(ij) under isotropic and anisotropic loading conditions. The new model also offers a new method for determining the fabric anisotropy of sand based on the anisotropy of shear modulus.