Study On The Reinforcement Mechanism Of Loess Slopes With Amorpha Fruticosa Linn

Since the implementation of the western development strategy,large-scale highways and high-speed railroads have been built in the loess areas,which have destroyed the native plant communities and caused serious ecological and environmental problems.Therefore,the use of vegetation for slope protection has become a "mandatory subject" in the construction of engineering projects.Based on the ecological protection project of loess slope of Lixi Expressway in Shanxi Province,this paper discusses the theoretical basis of slope ecological protection based on field investigation and theoretical analysis,and analyzes the reinforcing effect of vegetation on the slope soil body.Through a combination of indoor tests and numerical simulations,the influence of the content and distribution of the root system of Amorpha fruticosa Linn in the loess on the mechanical properties of the soil and its influence on the stability of the slope is studied,and the mechanism of the reinforcing and anchoring effect of the vegetation root system on the soil is revealed.The main research contents and conclusions of this paper are as follows.(1)In order to investigate the influence of the diameter and growth year of the root system on its tensile strength,single tensile tests of the same diameter with different years and the same year with different diameters were carried out in this paper.The test results showed that the tensile strength of the root system was higher in age 1 than in age 2 when the diameters were the same.With the increase of diameter,the tensile strength of 1-strain roots decreased more rapidly than 2-strain roots.The tensile strength of the root system was negatively correlated with its diameter as a power function when the root system diameter was 0.5 mm-2 mm at the same age.(2)In order to investigate the influence of root content and root distribution on the shear characteristics of root-soil composite structure,direct shear tests of root-soil composite with different root content and different root distribution were conducted under different water content conditions.The test results showed that when the water content was 9.31% and 15.65%,the internal friction angle of the root-containing soil body increased with the increase of root content,but the cohesion decreased.When the water content was 17.44%,the internal friction angle and cohesion increased with the increase of root content.For different root laying methods,the maximum values of root-soil complex cohesion appeared in the order of horizontal root laying,vertical root laying,and twenty-shaped root laying with the increase of water content.(3)In order to investigate the influence of different slope shapes,root lengths,angle with lead hammer direction and distribution methods on slope stability,this paper uses the finite difference software FLAC3 D for simulation analysis.The results show that: the safety coefficient of slope gradually decreases with the increase of slope angle,and when the slope angle reaches 53°(1:0.75),the change of increment of safety coefficient becomes less and less obvious,which indicates that vegetation can no longer play a good protective effect on slope soil when the slope angle is greater than 53°;when the root system is staggered and the angle with the lead hammer direction is 30°,the protection effect on slope is the best.