Study on Single Shear Characteristics and Deformation Modeling at the Root-Soil Interface of Robinia Pseudoacacia in the Loess Plateau

The superimposed effects of extreme rainfall events and engineering disturbances in the Loess Plateau have led to a significant increase in the risk of shallow loess landslides. This situation reveals the engineering governance contradiction of "ecological improvement vs. disaster intensification" in ecological restoration projects. This study focuses on the mechanical properties of the root-soil interface of Robinia pseudoacacia. Through methods including in-situ testing, single shear test, and theoretical analysis, we systematically quantified the multi-field coupling effects of moisture content fluctuations, root topological types, and variations in root content on the shear strength evolution of the root-soil interface. The results indicate: ① Vegetation roots in the shear strength characteristics of the root-soil interface. The shear process can be divided into three stages: initial linear elastic deformation, damage accumulation, and progressive failure. ② The stress-strain curves of the root-soil interface can be categorized into softening and hardening types, with the softening type comprising a strength-increasing phase followed by a strength-decaying phase. ③ A predictive model considering the stress-strain softening of the root-soil interface was proposed, demonstrating favorable predictive performance. This research provides essential data and theoretical support for ecological restoration in rapid slope stability assessments that incorporate vegetation factors.