| Vegetative embankment is the mainly form of engineering protection in river channel slope protection nowadays,its principle is to use interaction between planting roots with the characteristic of roots or stems and soil to achieve the actual protection.Not only planting stems and leaves can intercept the process of raining,control the surface runoff then reduce the loss of soil and water conservation,but also the photosynthesis of plants and hydrological effect can be controlled to reduce the environment pollution and purify air,provide a beautiful and agreeable environment for person;At the same time,the suction decompression effect of plant root system also can reduce the soil pore water pressure,the existence of root system with complex intertwining through the soil to raise the shear strength of soil and have a reinforcement effect on soil.This article is based on the channel slope with planting tall fescue,on slope soil erosion test method,through the scour depth indicator to measure the resistance to erosion of slope soil,and soil to root complex direct shear test,research on shear strength index of root and soil interaction,so as to illustrate the influence of the existence of the root system on soil erosion resistance.Tall fescue as the research object which is the common slope protection planting in Liaoning province,in this experiment,the density of tall fescue was divided into high density and low density and the height was controlled by the method of artificial pruning respectively,18cm,12cm,6cm,Ocm.The main test contents are:(1)Slope planting tall fescue experiment on the different growth density and the different heights of tall fescue in the condition of same scouring duration and five different flows respectively(11.63 L/s,25.18 L/s,33.47 L/s,45.39 L/s,55.37 L/s),reach the conclusion that the influence of tall fescue growth density and plant height on the scouring resistance of soil erosion by the value of scouring depth.(2)Select root soil complex with two different growth densities of tall fescue in three different soil depth to do direct shear test and measure the soil shear force when it in four different vertical pressure(50kPa 100kpPa,150kPa,200kPa),it will give a conclusion about the influence on the plant density and height of complex root soil shear resistance;(3)Measure the root indicators,such as length density,average diameter,surface area and biomass specific features of root in the soil samples roots on DT-SCAN root analysis system,it will give a conclusion about the relationship between the biological characteristics of root and the cohesive force and angle of internal friction,in other word,the relationship between the root system and the soil resistance to shear failure with be given;(4)Measure the soil particle mechanical composition of tall fescue with different density after slope planting tall fescue scouring test,analyze the difference on the existence of the root system in soil and then study on the influence of soil scour resistance;The mainly research results showed:(1)There are positive correlated relationship between the height and density of tall fescue and root soil anti-scouring ability.When the tall fescue have the same density,the root soil complex of scour depth decreases with the increase of plant height,especially the scour depth with plant height of 16 cm is smaller than the scour depth with plant height of 0 cm,the value of scour depth decreased by 46%on average.In the certain circumstances of plant height,the root soil complex of scour depth decreases with the increase of density of plant growth,scour depth with high density less than scour depth with low density about 52%.(2)Shear strength of tall fescue and root composition has a relationship with tall fescue planting density and the depth of in soil,when the samples in the same soil depth,with the increasing of the growth of planting density,the cohesive force and angle of internal friction of complex are getting bigger,in other words,the ability of resist shear break is stronger.There is a positive correlation relationship between the planting density and the ability of resist shear break;When the tall fescues with same planting density,with the increasing of the soil depth,the cohesive force and angle of internal friction of complex are getting smaller,in other words,the ability of resist shear break is weaker.There is a negative correlation relationship between the soil depth and ability of resisting shear strength;(3)There are certain positive correlation relationship between the length density,average diameter,surface area and biomass specific features of root and cohesive force and angle of internal friction of soil and scour depth.The root length density with the cohesion force and the angle of internal friction have a exponential relation,the formula is ρ=0.7894e1.5952C and ρ= 3E-08e0.2475C,with the scour depth of soil presents a linear relation,the formula is ρ=-0.3024z+23.953;Root average diameter presents a linear relationship with cohesive force formula is D=0.0717C+0.3377,the angle of soil internal friction and scour depth also presents an exponential relation and formula is D=0.0454e0.0629φ and D=90.757e-1 6938z;Root surface area,the angle of soil internal friction and scour depth also present exponential function relation,formula are ρ=9.9435e0 0959C、ρ=0.0013e0.1944C and ρ= 24.189e’0 01832C;Root biomass and soil cohesive force rendering logarithmic relation formula is m=0.4136Ln(C)-0.5257,the angle of soil internal friction and scour depth also present exponential function relation,formula is m= 0.008e0.12φ and m= 37.505e-2 2006z.(4)The soil particle composition in soil,low density and high density change with difference of scouring flows,but no matter under what kind of flows,the soil particle size in 0.5～.0 mm and less than 0.075 mm take bigger in the total quality percentage,and the soil particle size more than 2.0mm and in 2.0-0.25mm particles take bigger in the total quality percentage is relatively small.The content of small size of soil particle reduces faster with the increase of flow,and low density tall fescue times,the content of small size of soil particle in high density of tall fescue soil reduces slow with the increase of flow. |
