Understanding shear mechanisms in rooted soils using fibre-optic instrumented 3D-printed roots

Abstract

Vegetation can increase soil shear strength, yet the mechanisms governing root reinforcement remain difficult to quantify due to limited direct measurements. This communication presents a methodology that combines resin-based 3D-printed synthetic roots with distributed fibre-optic sensing to measure root deformation during direct shear tests in sand. Short and long bio-inspired root systems were tested in sand using resin mixtures with contrasting stiffness. Short roots produced a frictional response with similar peak strengths for stiff and flexible resins, consistent with their acting primarily as geometric asperities along the shear plane. In contrast, long roots generated higher shear resistance and an approximately linear increase in shear stress with displacement. Fibre-optic measurements revealed progressive mobilisation of tensile strain along the embedded length, indicating reinforcement through the formation of a soil–root composite tying the specimen halves together. The results demonstrate the potential of combining 3D printing and distributed sensing to investigate root–soil reinforcement mechanisms.