Salix integra Root Reinforcement in Canal Slopes: Direct Shear, FracRoot, and Deterministic Stability Assessment

Vegetation-based nature-based solutions can improve shallow slope stability, yet transferring root-scale measurements to slope-scale assessment remains difficult. This study reanalyzes archived mechanical and engineering data for Salix integra used on an ecological canal embankment in northern Jiangsu Province, China. The dataset comprises 36 peak shear stress increments from constrained single-root direct shear tests conducted at four normal stresses and nine root-diameter classes, together with ten bifurcation records used for FracRoot reconstruction. Peak shear stress increment, Δτ, ranged from 2.41 to 39.28 kPa. Normal stress was the strongest statistical predictor within the clamped-end test configuration (r = 0.849, p < 0.001), whereas root diameter showed no significant unadjusted effect. The preserved FracRoot relationships were Dmax = 0.820D0 and Dmin = 0.563D0. An archived deterministic double-wedge calculation reported a factor-of-safety change from 0.92 to 1.14 after inclusion of aggregate root resistance. Because the separate unreinforced peak values, complete shear records, direct field root-depth measurements, planting geometry, and segment-level root-intersection calculations were not preserved, the statistical analysis is restricted to archived increments and the stability result is interpreted as an illustrative scenario rather than a verified design value. The novelty lies in transparently linking archived root-scale testing, branching architecture, and local slope-stability assessment while defining the evidence required for reproducible field-scale validation.