Abstract: Current research on the mechanical properties of plant root systems in soil reinforcement is mostly limited to isolated root groups or localized root samples. To explore the mechanical mechanism of root-soil interaction in the entire root system, a 3D reconstruction model of the complete root system of Moso bamboo was developed through holistic modeling of the Moso bamboo root system. Using ABS-like photosensitive resin, a material possessing mechanical properties similar to real roots, a complete root system model was fabricated by 3D printing technology. Large direct shear tests were conducted to analyze the mechanical properties of the root-soil composite. The results indicated that the morphology and structure of the root system significantly influences the mechanical properties of the root-soil composite. At cross-sections with sufficient root density, the shear load can be collectively borne by the entire root system. The robust root structure facilitates the mobilization of the entire root network to resist shear loads. The root system can enhance both the cohesion and internal friction angle of soil. In granite residual soil, higher vertical stress promotes close contact between the roots and soil, resulting in an accelerated increase in shear strength. Based on the experimental results, an empirical formula for calculating the shear strength of the complete root-soil composite system was proposed. The findings provide scientific evidence for further elucidating the mechanical interaction between roots and soil and introduce a novel, controllable, and repeatable experimental method for studying soil reinforcement effects of roots.

Key words: root-soil composite, 3D printing, large direct shear test, root-soil interaction, root reinforcement model