Abstract: The aim of this study is to investigate the reinforcement effect of herbaceous plants in opencast mine dump area. Three locally grown herbaceous plants, Poa annua L., Suaeda glauca Gunge, and Digitaria sanguinalis Scop. are selected as research objects. Through tensile strength test and in-situ shear test on plant roots as well as Wu-Waldron model (WWM) calculations, the correction factor of WWM model is determined, and then the corrected WWM model is used to quantify the root cohesion of herb plants in the dump site in association with the geometric distribution characteristics of roots on soil profiles at different depths. Results demonstrate that the tensile strength of the three herbaceous plants has a power-law function relationship with root diameter, decreasing nonlinearly with the increase of diameter. Significant (p<0.05) differences are found in the tensile strength of the three herbaceous plants. In comparison, the root-soil composite reinforced by Digitaria sanguinalis Scop. provides larger shear resistance, and also greater stability after peak shear force. WWM model overestimates the reinforcement effect of plant roots, and the degree of overestimation varies with species. Moreover, the WWM model for the three herbaceous plants are modified, and the correction factors are 0.58, 0.27 and 0.88, respectively. Both the root area ratio and root cohesion of the three herbaceous plants decrease with the increase of soil depth. Digitaria sanguinalis Scop. has the best reinforcement effect in the local area.

Key words: herbaceous plant reinforcement, dump site, root cohesion, root-soil composite, in-situ shear test