Stability Research Of Vegetative Soil Layer By Anchor-Geomat Spraying Ecological Slope Protection Based On Experiments And Numerical Simulation

The dramatic development of the economy in recent years promoted the rapid growth of the infrastructure construction in our country. However, due to the excavation and filling in the construction phase, the original vegetation was destroyed and a large amount of secondary bare land was produced beside the rock slopes, which have negative effects on the ecological environment and cause serious disasters that endanger public security, such as landslide and debris flow. Thus, the technologies regarding the vegetation recovery and ecological protection of rock slopes gradually become a hot issue. The current ecological protection technologies mainly focus on the stability of the deep layer of the side slope. While the surface vegetation on side slopes was mostly laid according to construction experience and the condition of the construction area, there is a lack of systematic theoretical instruction about the stability of the vegetative soil layer where the surface vegetation grows. This thesis focuses on the stability of the vegetative soil layer that was laid using anchor- geomat seeding vegetation slope protection technonogy, which is an integrated ecological slope protection technology. The research combines field and lab experiments and mathematical modeling approaches, and has great practical and engineering significance.In this thesis, the water content and shear strength of the vegetative soil layer were measured through field experiments; the experimental results were used as the reference values of the vegetative soil units in the mathematical model. The variation of water content and the displacement along the slope direction as well as the deformation rules in the vegetative soil layer were analyzed. The main content and conclusions of this thesis are as follows:(1)The angle of the rock slope, size of the 3D geomat, and the vegetation density were included in the field experiments. The water content and the corresponding shear strength of the soil layer that contain the vegetation roots were measured at the exuberant stage of the vegetation growth; precipitation simulation was performed to analysis the infiltration process of rainwater in the vegetative soil layer, as well as the water content and shear strength under saturated condition of the soil layer. Moreover, the water content at different locations on the slope surface and different depth in the soil layer were measured to study the parameters that have impacts on the water content variation in the vegetative soil layer.(2)The angle of the rock slope, size of the 3D geomat, the vegetation density, and the thickness of the vegetative soil layer were applied in the mathematical model developed through FLAC3 D software. Laboratory results of the shear strength of the soil layer measured with various water content were utilized as the reference values of the vegetative soil units in the mathematical model. Subsequently, the displacement along the slope direction as well as the deformation rules in the vegetative soil layer were analyzed.(3)The vegetation could reduce the runoff and protect the soil on the surface of the slope during precipitation. It is also beneficial to maintaining surface moisture of the vegetative soil layer after precipitation. Meanwhile, the geomat changes the permeability of the vegetative soil and inhibites the change of water content in the vegetative soil layer, which is good for the water storage capacity and the stability of the soil layer.(4)A negative correlation was observed between the stability of the soil layer and the vegetation density; while the stability of the soil layer was positively correlated with the thickness and water content of the vegetative soil layer and the slope angle. According to the results of field experiments and mathematical simulation, the thickness of the vegetative soil layer can be 15 cm when the angle of the slope was 45°; the thickness of the vegetative soil layer can be 10 cm when the angle of the slope was 60°; and the thickness of the vegetative soil layer can be 5 cm when the angle of the slope was 70°.