Study On Mechanical Properties And Slope Stability Of Reinforced Expansive Soil With Vetiver Root

With the acceleration of economic development,a large number of artificial slopes have been formed through excavation along with the construction of highways and railways.At the moment of both efficiency and environmental protection,ecological protection has become a hot spot.Because vetiver has the characteristics of developed root system,high drawing strength and easy survival,the application effect in the difficult-to-treat expansive soil slope protection project is worthy of study.Based on the existing research results,through direct shear test,expansion force test,penetration test,stability analysis and seepage analysis,the effect of vetiver grass on soil properties and slope stability in expansive soil slope protection are obtained.The results could provide reference for the ecological protection research of later expansive soil slope.The main contents are as follows:(1)The indoor direct shear test was carried out on remolded expansive soil samples with different water contents under different root densities.The test results show that the presence of roots can significantly improve the shear strength of the samples.With the increase of the sample water content,the cohesion,internal friction angle and shear strength of the root-soil composite gradually decrease.Therefore,controlling the water content of the slope is the key to keep stability of the slope.(2)Through the expansion force test,it is found that the expansive soil is sensitive to water,the expansion force of the sample reaches the maximum at the optimum moisture content.However,the higher the root content of vetiver,the more the swelling is inhibited.According to the variation of the expansion force with the root content under different soil water content,it is found that the higher the water content,the less the root content is required when the sample's expansion force is the weakest.(3)The indoor water head penetration test of samples under various root contents was completed.By observing the variation of the permeability of the samples with the content of the root system,it was found that the root samples were significantly higher than the soil samples.When the root density was higher,the permeability coefficient of the sample at the standard temperature was also larger,it indicates that the main root system of vetiver can improve the permeability of expansive soil to a certain extent.(4)The safety factor of expansive soil slope under the influence of various factors was analyzed by Slope software,the effects of root density,water content of root-soil composites and expansion forces on slope safety were studied.The simulation results showed that when the root density gradually increased,the slope changed from unstable to steady state;when the water content gradually increased,the slope stability became worse.The expansion force in the lower part of the slope has the greatest influence on the stability of the slope,followed by the upper part,and the top expansion force has the least influence on the stability.Therefore,the methods and measures for dealing with the protection of the lower slope in actual engineering need to be studied.(5)Based on the test of the influence of root content on soil penneability coefficient,the SEEPAV software was used to analyze the results of volumetric water content at different locations of the slope caused by rainfall.The results show that in the rainfall stage,the increase of volumetric water content is proportional to the root density and elevation.When the rainfall stops,the decrease speed of volumetric water content is inversely proportional to the root density,and the degree of declining is proportional to the elevation.The closer the feature point depth is to the slope surface,the faster the water content increases,and the time to start to fall is also earlier than the deep position.