Abstract: At present, the quantitative evaluation models of mechanical reinforcement of soil by roots lack consideration of root-soil interface bonding effect. In order to improve the accuracy and applicability of the quantitative model, this study was premised on the widely used Wu model, combined with the failure mode of root system in root-soil, and quantified the bonding effect of interface between root and soil interface by interface bonding strength parameters. Thus, an estimation model of limit values of shear strength of root-bearing soil based on interface bonding was established, which considered the influence of soil stress, root diameter, root length, and initial angle between root and shear direction in root-bearing soil. Furthermore, the comparison of shear strength of root-bearing soil between the measured values of direct shear test and the calculated values of the model showed that the measured values were within the range of the calculated values of the model established in this article. When the angle between the root and the shear direction was 45°, the measured value was close to the maximum value of the model calculation, and when the angle was 90°, the measured value was close to the average value of the limit values of the model calculation. Compared with the calculated value of Wu model, the accuracy of the estimation model established in this article was increased by five times on average. Moreover, the sensitivity analysis of model parameters showed that the additional soil strength provided by roots was greatly affected by the root number parameters, root size parameters and root-soil interface bond strength parameters.

Key words: root-bearing soil, root-soil interface bonding strength, shear strength, mechanical model