Fig. 2: Causal pathways and strength of subgrade defects in high-speed rail.

a Subgrade settlement, b Frost damage, c Uplift deformation, and d Mud pumping. Standardized path coefficients are displayed alongside the directional arrows, quantifying the hypothesized influences, where the arrow’s thickness represents the relationship’s strength. Significant path coefficients are marked with asterisks, indicating levels of statistical significance (*p < 0.05, **p < 0.01, ***p < 0.001).