Research On The Interaction Of Vegetation Root And Soil For Highway Grass Slope

Planted grass is one of ecological slope protection method,it is close to natural way to strengthen and stable slope.The theory of vegetation root solid earth is in preliminary research phase,because planting the grass species of diversity,the randomness of root distribution,the fluidity of root strength and so on.With vetiver grass roots as the research object,firstly it studied the formation distribution of root.And then three tests were carried out to study the tensile strength of single root, characteristics of the root and the interface and strength propetry of root-soil composite.For the research of root tensile strength,the test apparatus was pendulum type paper anti-spasticity tester.The influence factors of root tensile strength were studied,including the moisture content, root diameter and root length.Test results showed that,tensile strength was the largest when the root airing a day and night;the root diameter was greater,the strength was lower in the same root length;the root length was longer,the strength was lower in the root diameter were roughly equal.The test apparatus of the research of characterristics of the root and the interface was strain control type direct shear apparatus.It obtained that interface cohesion,interface friction angle,interface friction coefficient and friction coefficient ratio of root-soil composite interface were greater than soil's through direct shear tests of soil and root-soil composite.This explained that the existence of root can increase the frictional resistance between the root and soil,and increase the intensity of the soil.The paper adopted triaxial shear penetration test apparatus to research the strength propetry of root-soil composite.The change of shear strength indexes of root-soil composite with the quantity of grassroots and water content in the soil samples was investigated.Laboratiry triaxial tests were carried out in order to understand the stress-strain relationship and strength propetry of root-soil composite.The strength property and the failure modes of soil and root-soil composite were contrasted.Finally mechanics effect of root solid earth was analyzed.The finite element calculation model was established when we putted deep rough roots as anchor,and shallow roots and surrounding soils as uneven medium.It analyzed the influence of vegetation on the whole stability of the slope.The results showed planting vegetation to play the role of reinforced slope .