Research on Mechanism and Mechanical Model of Sandy Soil Reinforced by Herbal Roots

Herbs have well-developed roots with high tensile strength, which can effectively stabilize slopes. This study took the roots of common herbaceous plants, such as bahia grass (Paspalum notatum) and tall fescue (Festuca arundinacea), as research objects to study and quantify the effect of herbal roots on soil reinforcement. The shear resistance parameters of the undisturbed soil with and without roots were measured through direct shear tests. The measured increase in shear resistance of the soil permeated with roots was obtained to compare with the value predicted by the WU model. The influence of species and planting density on the effect of reinforcement was analyzed. The results showed that the tensile strength of the roots decreased as their diameter increased. The roots of bahia grass are primarily distributed vertically in the soil, while those of tall fescue grow like a net. The roots have a significant effect on enhancing soil cohesion, but they have little effect on the angle of internal friction. Herbal roots primarily strengthen the superficial layer of the soil. The value of k was revised to 0.14 to increase the accuracy of WU model to predict the value of typical herbal roots in strengthening sandy soil. The result was verified, and the predicted value of the revised WU model was very close to the measured one, with a ratio of 0.95: 1.07. These results can provide technical support and a theoretical reference for the mechanisms used by herbs to strengthen the slopes of sandy soil banks.