Research on mechanism of soil reinforcement and slope protection of herbaceous plant roots in advanced rainfall pattern

Destruction of slopes and their protection works are often caused by rainfall. For the implementation of ecological restoration projects on the shorelines in our country, using the root system of (10 + 10) g/m² Agrostis stolonifera + Paspalum notatum Flüggé grown for 12 months as an example, the mechanism of soil reinforcement and slope protection of herbaceous plant roots in advanced rainfall pattern is researched. In this paper, matric advanced rainfall pattern is simulated for deformations of slope and variation of water content, pore pressure and suction. An expression of the relation of hydraulic characteristics of bare soil and root soil is obtained. A new stability analysis model under rainfall at a specific time is proposed for explaining the impact of depth and rainfall duration on stability factor. The results show that: (1) In advanced rainfall pattern, the stability of the soil slope is more susceptible to the effects of the early 150 mm/h rainfall compared to vegetated slopes, and the impact of subsequent 50 mm/h rainfall on the stability of the vegetative slope is relatively minor; (2) Herbaceous roots improve the stability of 30 cm depth of root soil layer, deteriorate the stability of 35 cm to 60 cm soil medium layer near root soil layer. Soil layer deeper than 100 cm is lightly influenced by roots; (3) Herbaceous roots can prolong the stability of slope, reduce soil erosion, and protect soil and water. However, herbaceous roots should work with other engineering structures for the long-term stability of bank slope. This paper provides necessary data base and theories for the construction of ecological bank protection projects in the middle and lower reaches of the Yangtze River.