Research On The Strength Characteristics Of Root-soil Complex Based On The Theory Of Flexible Reinforcement

As a green means to solve the green slope soil shallow landslides,soil erosion and other ecological problems,ecological slope protection technology not only realize the effect of soil consolidation and slope protection,but also can improve the slope of the surrounding environment and promote ecological balance.Currently,root for the status quo-research strength characteristics and intensity of soil composite model still remain to be improved,which have become a bottleneck restricting the popularization of the ecological slope protection technology.To solve this problem,binding to the solid earth rooted was studied to obtain a root undisturbed-soil composite intensity calculation model by theoretical and experimental methods.Flexible Reinforced soil composite strength model was optimized base on the theoretical and experimental results.In this study,tests comprises a root and mechanical performance test,roots-complex shear test soil.The test results is used to study the mechanism of root reinforcement of soil,test and optimize the existing reinforced flexible model,and establish root-soil composite strength model which regards the root mass density(RMD)as the key calculation parameters.The study has some theoretical significance and application value.The thesis is supported by the National Natural Science Youth Fund Project "Research on the Mechanism of Plant Slope Soil Consolidation Based on Root Architecture Directional Control"(Project No.51608545)and the Science and Technology Research and Development Project of China Railway 20th Bureau "Ecological Slope Technology in Chongqing Railway Hub East Loop Project" "Application Research in China"(Project No.YF1900SD07B).In these projects,the common red clay and slope protection plant vetiver in Hunan was selected as the objects of the tests,and the root-soil composite strength characteristics test and root soil consolidation theory research was carried out.The main research results and innovative conclusions are as follows.(1)The test of measuring the mechanical properties of the root system of vetiver showed that cultivation conditions such as poor soil quality and anhydrous fertilizer management will significantly reduce the mechanical properties of the root system of vetiver.With increase of the diameter of the root system of vetiver,the tensile strength of the root system increases,while the tensile strength of the root system decreases in the test.Root distribution testing experiments show that the root mass density(RMD)has a significant parabolic function relationship with the soil depth.With decrease of the soil depth,the distribution of root in the soil becomes denser and the RMD increases.(2)The indoor root-soil composite shear test proves the shear characteristics of the root-soil composite.The test results show that the shear strength of root-soil composite increases with decrease of the depth.The shear stress of the root-soil composite and its growth rate are less than that of the plain soil when the shear displacement is within 0-3 mm;the shear stress of the root-soil composite gradually approaches and exceeds the plain soil when the shear displacement exceeds 3 mm.The gap gradually increases with the increase of soil shear stress and shear displacement;and the peak corresponding shear stress and the peak corresponding shear displacement increases with the root-soil composite root density.(3)The results of root-soil composite shear test shows that the peak shear stress and the overall shear strength increases with the root density under the same vertical pressure conditions.When the shear failure occur in the root-soil composite,the roots in the soil will slide by the force but the sliding friction force is less than the ultimate tensile strength of root.Spearman correlation analysis showed that correlation between the density of RMD is strongly correlated with the root-soil cohesion c,and weakly correlated with friction angle ?.Therefore,the root mass density(RMD)can effectively influence the root-soil cohesion c,but the effect on the friction angle ? is weak.(4)A root-soil composite flexible reinforcement optimization model is Established with the root mass density(RMD)as the core calculation parameter.In the optimization model,the root number n is replaced with the root mass density(RMD)that is convenient to measure.Therefore,the shortcomings such as the parameter measurement in the original model difficult and influenced by human factors greatly is overcome,so that the objectivity of parameter can be ensured.Furthermore,the root-soil composite strength can be more easily and accurately calculated in the optimization model.