| In recent years, with the Chinese economy developing rapidly, the country infrastructure investment is increasing. A large number of infrastructure construction provide a convenient environment and improve the quality of people’s living, but it impact the ecological environment. Especially for the large infrastructure construction in mountainous and hilly areas, such as highway, railway and so on.It can not avoid the high filling and deep excavation, resulting in damaging to the original plant and soil structure, and some even causing the bare slope. Part of the artificial slopes are the existence of security risks, such as collapse, landslide erosion, etc. There will be more severely damage to the food chain, water and soil erosion and other environmental problems. The traditional engineering protection measures are relatively mature. It can better reinforce slope, but there are also shortcomings, because the traditional engineering protection of vegetation growth is closed, which is unfavorable to the sustainable development and environmental protection.Compared with the traditional slope protection technology, the Ecological slope protection technology has more advantages, such as good landscape effect, low cost and long service life. Ecological slope protection has been used widely in slope protection of highway, water conservancy and hydropower engineering. In the research field of ecological, slope protection in the roots soil mechanics is becoming a hot issue of research. Based on the existing research in the world, this paper research Bermuda grass and Manila grass and clay soil in Changsha, which form root complex, The thesis rely on science and technology project in Changsha"Study on the technology and promote the restoration of ecological highway in Changsha"(project number:K1205028-11) and the Central South University of Forestry and Technology Graduate Innovation Fund (project number: CX2013Z41) to carry out the related research, the main work and the main conclusions of this paper are:1. Investigated municipal road slope in Changsha researched the growth of Bermuda grass and Manila grass. Studied distribution and density of roots. The roots density decreases with soil depth increased, getting the constitutive equation.2. Based on the direct shear test of roots soil composite, researched the relationship between shear strength and roots content, as well as the constitutive equations of cohesion and internal friction angle of the roots soil complex and root content,calculation results and measured data are in good agreement, and the conclusion:(1) The vertical stress effect on shear strength, vertical stress shear strength showed a linear relationship with shear strength. With the increase of vertical stress, the shear strength increases linearly.(2) Roots on soil effect shear strength. The more number of roots are, the stronger shear strength is.But with the increase of roots number, the shear strength increase slow down gradually。(3) The roots influence internal friction angle unobviously, but the cohesion increased significantly, which is equivalent to the root to increase the cohesion and improve the shear strength of soil.(4) The shear strength of root-soil systems is relative to moisture content in soil. The lower the moisture content, shear strength of root-soil composite stronger.(5) In two kinds of moisture conditions,the increase of the shear strength value of Bermuda grass soil complex is greater than Manila grassroots soil complex.(6) Got the constitutive equations of cohesion and internal friction angle of the root soil complex with roots content. Cohesion and roots content is the law of logarithmic function;the internal friction angle and the root content showed a linear function.3. According to slope of road. The slope stability coefficient of different root density was calculated by the Swedish slice method. The stability coefficient of the slope increased by the root density increase. Got the constitutive function of root density and stability coefficient. |
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