Study On The Bending Characteristics And Slope Protection Effect Of Vine Honeysuckle Under The Action Of Flow

Plant slope protection is widely used in engineering slope protection because of its good environmental friendliness and economy.In extreme weather conditions,there is the possibility of overflow on the slope.Flexible vegetation will bend and deform under the action of flow to form blanket protective layer on the slope surface.Thereby the bottom velocity of slope flow is reduced;the scouring effect caused by slope runoff is weakened,and soil erosion and protecting slope safety is prevented.However,there are few studies on the deformation characteristics of flexible vegetation under flow and its protection effect on slope surface,which restrict the further development and application of ecological slope protection.Combined with theoretical analysis,numerical simulation analysis and field test,the deformation and bending characteristics and slope protection effect of vine honeysuckle which is a new type of flexible plant for reservoir slope protection under water flow were studied.The theoretical formula of the bending height of vine honeysuckle under the action of water flow was derived based on the theory of large flexible cantilever beam;the mechanical properties test and bending characteristics test of single plant honeysuckle stem under water flow were carried out,and the interaction law between single plant vine honeysuckle and flow was studied by two-way fluid-solid coupling numerical simulation analysis.Based on Lijiazhuang Reservoir,the slope protection characteristics of different vegetations including vine honeysuckle vegetation were studied.The results can provide reference for the anti-scour mechanism of flexible vegetation and the application of slope protection vegetation.Specific research results include the following aspects :（1）Bending characteristics of vine honeysuckleCombined with the stress of flexible plants in flow,the theoretical formulas for the angle and bending height of each point after the bending of vine honeysuckle were deduced based on the theory of large flexible cantilever beam.The comparison between the theoretical calculation results and the experimental results showed that the calculation formula could better predict the bending height of vine honeysuckle under the action of flow.（2）Mechanical property test and bending property test of single vine honeysuckle under flowThe elastic modulus and bending strength of honeysuckle stems decreased with the increase of diameter,and there was no significant difference in the mechanical parameters of stems with different diameters.The average value was taken as the material parameters of theoretical calculation and numerical simulation.The bending height of vine honeysuckle decreased with the increase of flow velocity,and the error between the experimental results and the theoretical calculation was small.（3）Fluid-solid coupling analysis of vine honeysuckle under flowBased on CFD numerical simulation technology,the bidirectional fluid-solid coupling simulation of vine honeysuckle under flow was carried out.The simulation results showed that the flow generates a flow around the honeysuckle structure,and the flow velocity on both sides of the vine honeysuckle increases,forming an elliptical shelter zone with low flow velocity on the back surface.With the increase of the vine honeysuckle structure bending,the range of low flow velocity zone extends along the flow direction.The tensile stress of the honeysuckle structure is the largest at the upstream flow;the compressive stress is the largest at the back flow,and the shear stress at the upstream of the top branch of the honeysuckle structure is the largest.（4）Slope protection characteristics of different vegetationsThe surface flow velocity of sage vegetation slope protection,vine honeysuckle vegetation slope protection and mixed vegetation slope protection increased with the increase of flow.When the flow rate is 100 L/min,the flow velocity of sage vegetation slope protection is obviously smaller than that of honeysuckle slope protection and mixed vegetation slope protection,and its resistance coefficient is the largest.When the flow rate increased from 200L/min to 300 L/min,the flow velocity increased rapidly and the resistance coefficient decreased significantly.When the flow rate is 400 L/min,the resistance coefficient of honeysuckle is significantly higher than the other two types of slope protection.After passing through the water,obvious erosion pits appeared on the slope protection surface of sage grass,and no obvious erosion pits appeared on both sides of honeysuckle stem.The above conclusions show that under the condition of over-flow on the slope,vine honeysuckle,can effectively increase the slope resistance coefficient.Vine honeysuckle,bends and lodging,effectively reduces the near-bottom slope flow velocity and weakens the runoff shear force,which verifies the feasibility of vine honeysuckle,as an ecological slope plant.