A Study On Geotechnical Characteristics Of Amorpha Fruticosa Root-soil Complex

In this thesis,the root system of the shrub Amorpha fruticosa widely distributed in central and western Inner Mongolia was taken as the research object.Through indoor single root pull-out test and direct shear test,the strength characteristics of Amorpha fruticosa root system and silty sandy root-soil composite-soil interface friction properties.In order to improve the mechanism of plant root soil fixation,and provide a theoretical basis for the selection of soil and water conservation plant species in the study area.The research results are as follows:(1)The shear strength of Amorpha fruticosa root-soil composite is linearly positively correlated with the vertical load.The deeper the root system,the stronger its ability to hold the soil;the root system significantly improves the shear properties of plain soil,The shear strength of the root-soil complex was significantly higher than that of the plain soil;the residual shear strength of the root-soil complex of Amorpha fruticosa root-soil was higher than that of the plain soil,which meant that the root system of Amorpha fruticosa root system could still play the role of soil fixation after being subjected to shear damage.(2)The shear strength,residual shear strength,and root diameter of the Amorpha fruticosa root-soil complex are all positively correlated;with the increase of soil moisture content,the strength characteristic index The indexes of residual shear strength and residual shear strength showed a trend of first increasing and then decreasing;the larger the bifurcation angle,the greater the shear strength and residual shear strength of Amorpha fruticosa root-soil complex,and the bifurcation angle was 61-90° The shear strength of the rootsoil complex increased by 11.67% and 19.38% compared with the shear strength at angles of 31-60° and 0-30°;The shear strength is as follows: branched root section > straight root with fibrous root section > straight root section,and the shear strength of the root-soil composite of the straight root with fibrous root section is 1.2 times higher than that of the straight root section.(3)The pull-out friction strength of the root-soil interface of Amorpha fruticosa increases exponentially with the increase of the root diameter;with the increase of soil moisture content,the pull-out friction strength of the rootsoil interface of Amorpha fruticosa increases first afterwards,the trend of decreasing;the bifurcated root of Amorpha fruticosa with a bifurcation angle of0-90°,the pulling friction strength of the root-soil interface is the largest when the angle is 61-90°,compared with 31-60° and 0-30° respectively increased by13.46% and 23.58%;under different root types,the pull-out frictional strength of the root-soil interface of Amorpha fruticosa is as follows: bifurcated root segment > straight root with fibrous root segment > straight root segment,in which the straight root with fibrous root The pull-out friction strength of the root segment is 1.3 times higher than that of the straight root segment.(4)The direct shear friction strength of Amorpha fruticosa root-soil interface is much greater than that of soil-soil interface,and the root system improves the friction strength of soil;With the increase of soil moisture content,the friction strength and cohesion of Amorpha fruticosa root-soil interface first increased and then decreased.When the soil moisture content reached about6.68%,the friction strength and cohesion of root-soil interface reached the maximum.With the decrease of shear rate,the friction strength,cohesion and friction coefficient of Amorpha fruticosa root-soil interface and soil-soil interface all increase.(5)According to the structural equation model,the degree of influence of different influencing factors on the soil-fixing ability of Amorpha fruticosa root system from high to low is: root-soil interface friction characteristics,root tensile mechanical properties,root morphology,soil water content Rate.The root morphology is the decisive factor affecting the soil-fixing ability of the root system of Amorpha fruticosa,and the soil moisture content is an important factor affecting the soil-fixing ability of the root system of Amorpha fruticosa.