Study On Anti Scour Mechanism Of Ecological Slope Protection Based On Grass Root Anchorage Effect

The mechanical effect of plant root system on soil is an important factor to improve the stability and scour resistance of slope structure.At present,the research on soil fixation mechanism of plant root system and its impact resistance under the flow of sheet is in a blank spot.In this paper,the common soil and water conservation plants,tall fescue and dogtooth root,were selected as the research objects.Firstly,through soil mechanics shear test and root topology analysis,the spatial distribution of shear resistance and root biomass characteristic value of different plant root soil complex was studied.Then,jet erosion test is carried out on the slope of plant model,and the erosion failure mechanism and erosion change characteristics of slope under different bank slope environment are compared.Finally,through comprehensive analysis,the internal law of erosion resistance mechanism of the whole flow under the soil fixation effect of plant roots is systematically revealed.The conclusions of this study can provide some reference for the technical development and engineering application of ecological slope protection,and the main conclusions are as follows:（1）The shear resistance index of Tall Fescue and dog root is similar,the friction angle and cohesive force of 0-2cm soil layer are slightly lower than that of peak soil layer（2-8cm）,and generally,it decreases with the increase of soil depth,and the order of magnitude is:tall fescue<dog root<plain soil;The root biomass characteristic values（root weight density,root surface area density and root length density）of Tall Fescue and dog root were similar to the change of shear resistance index;The biomass of root system was concentrated in 0-8cm soil layer,and the average value of tall fescue was higher than that of dog root.（2）The characteristic value of biomass（root weight density,root surface area density,root length density）and cohesion and internal friction angle were exponential function growth relations.The shear resistance of tall fescue root was higher than that of dog root under the same root system biomass.（3）Under certain conditions,the damage of plant slope protection is usually the only one.The erosion failure condition（the process of destruction）can be divided into five stages:weak failure,slight damage,moderate failure and complete failure.When the flow rate is0.8-1.6m/s,the two plant slopes are mostly mild or moderate damage,and the flow rate is mostly moderate damage and severe damage when the flow rate is 1.6m/s-2.4m/s.At 3.2-4m/s,the damage degree of both plants is close to complete failure.（4）The change law of the mean erosion depth D_AEand the amount of sediment loss M_LDSof the slope of tall fescue,dog root slope and plain soil slope under various conditions is similar and consistent,and the exponential function increases with the increase of the scour velocity,and increases linearly with the increase of the scour angle;The average erosion depth under various conditions is:tall fescue<dog root<plain soil,and the order of sediment loss is:plain soil<dog root<tall fescue;The mean erosion depth of fescue was lower than that of dog root;When the scour angle is certain,the△D_AEand△M_LDSof each angle are the maximum when the velocity is 1.6m/s,and the velocity decreases gradually after the velocity is higher than 1.6m/s.When the velocity of scour is certain,the trend of△D_AEand△M_LDSdecreases with the increase of scour angle.（5）The internal friction angle and cohesion are positively correlated with the average erosion depth,and the soil erosion resistance index is negative;The root biomass density,root surface area density and root length density were all exponential（positive correlation）with the average erosion depth,and logarithmic（negative correlation）with soil erosion resistance index.