Anisotropic behaviour of rooted soils: constitutive modelling

Plant roots enhance soil stability, offering sustainable solutions for mitigating slope failure, erosion, and liquefaction. Experimental studies on rooted soils have revealed anisotropic and stress-dependent reinforcement effects. However, the theoretical understanding of this anisotropic behaviour remains limited. To interpret these behaviours, an anisotropic constitutive model was developed within the anisotropic critical state theory framework, incorporating two independent fabric tensors to represent the evolving structures of soil and roots. New anisotropic variables (AB, AR) and a root network evolution rule were introduced to capture the progressive mobilisation of root tensile strength as roots reoriented toward the direction perpendicular to the major principal stress. The model successfully reproduced key features of rooted soil behaviour under monotonic loadings, providing a unified framework for predicting the complex mechanical response of rooted soils.