Experimental Study On Mechanical Properties Of Reinforced Expansive Soil With Vetiver Grass Root

With the start of the blue sky defense war,more and more attention has been paid to the ecological environment by the government and people.The technology of vegetation slope protection has also received more attention because of its unique ecological benefits.However,the research on vegetation slope protection technology is not mature,which restricts the popularization and application of vegetation slope protection.Therefore,in order to popularize the application of vetiver grass slope protection technology in expansive soil slope engineering,this paper adopted single pull-out test,direct shear test,variable head permeability test,cracking test to reinforce expansive soil with Vetiver grass.The study of mechanical properties can provide reference for engineering application.The main contents and conclusions are as follows:(1)The root-soil interface friction characteristics of vanilla root-reinforced expansive soil were studied by single indoor pull-out test.The results show that the drawing process can be divided into three stages according to the relationship between root pull-out force and pull-out displacement.Root geometric parameters have a significant impact on the maximum pull-out force.With the increase of root diameter,buried depth,volume or surface area,the maximum pull-out force of roots increases correspondingly.(2)through indoor direct shear test,the strength characteristics of vetiver grass reinforced expansive soil were studied.The results show that the shear modulus of expansive soil reinforced by Vetiver root system increases with the increase of root content;the shear modulus of expansive soil reinforced by Vetiver root system decreases with the increase of water content;the shear strength of expansive soil reinforced by Vetiver root system is higher than that reinforced by Vetiver root system.The shear strength of expansive soil increases with the increase of root content;the cohesion and internal friction angle of expansive soil reinforced by Vetiver root decreases with the increase of water content;the decrease of vetiver root mass to a certain extent does not make the reinforcement of root system disappear completely,and when the root system leaves the plant,the reinforcement of expansive soil will disappear completely.The reinforcement effect of the roots did not decrease significantly when the samples were kept for a short time.Therefore,the vegetation death on the slope would not have a great impact on the strength of the slope soil in a short period of time.(3)through the variable head penetration test,we studied the permeability characteristics of the vetiver grass reinforced expansive soil.The results show that the average permeability coefficient of expansive soil reinforced by Vetiver root is obviously higher than that of expansive soil reinforced by Vetiver root at room temperature,and the permeability coefficient of expansive soil reinforced by Vetiver root increases with the increase of root content.(4)The anti-cracking property of expansive soil reinforced by Vetiver root system was studied by the soil cracking test under outdoor natural conditions.The experimental results show that the drying shrinkage cracks of expansive soil reinforced by Vetiver root system with more root content occur later than that of expansive soil reinforced by non-vetiver root system or with less root content,and the crack width develops and stabilizes earlier;the higher the root content of vetiver root system,the higher the reduction rate of the maximum crack width,and when the root content is higher.For 26/100cm2,The maximum crack width reduction rate has reached 97.73%.Therefore,the root reinforcement of vetiver grass can obviously inhibit the shrinkage crack of expansive soil,and the higher the root content,the stronger the inhibition.