Experimental Study On The Mechanism Of The Vegetation Roots' Soil-reinforcement Mechanics

In recent years, with the rapid development of national economy, massive construction projects have been built all over the country, especially the various infrastructure facilities. It not only meets people's survival and livelihood, but also to some extent, destroys the natural the original ecological environment. In the infrastructure facilities, such as highway, railway, water conservancy and hydropower, there are a lot of ferreting out high fill, which destroyed the original structure of the soil and the original vegetation, and resulted in a large number of exposed slope. These artificial slope may has, such as landslides, collapses, landslides and other potential safety problems, also may lead to soil erosion, local micro-climate deterioration and the food chain breaking. Although traditional artificial slope reinforces slope, plays a significant role in the stability of the slope, they have the same shortcomings that in the early construction of retaining structure, can effectively reduce the slope instability and erosion degree. However, with the slope of rock weathering and aging of concrete increased, structural strength will be reduced, and its protective effect will be greatly reduced. Meanwhile, the traditional engineering protection measures completely closed environment for the growth of vegetation, destroyed the original ecological environment, and is not conducive to environmental protection and sustainable development.With people's improvement of environmental protection consciousness and environmental requirements, vegetated slope technology came into being. Compared with the traditional slope protection, vegetated slope technology has great advantages of low construction cost, long service life and good landscape effect, and is widely used in the slope protection and greening of engineering projects, such as highway, railway, water conservancy and hydropower now, gradually replacing the traditional single-slope protection works. In the vegetated slope project, vegetation mechanical effects of slope protecting is a hot issue of multidisciplinary research in recent years, has received extensive attention. This paper selected the herb cynodon dactylon and the woody plants nerium oleander, which are commonly used in Hangzhou and Nanjing highway, to do the related mechanical research. The major work done and the main conclusions obtained are as follows:(1) Within the highway vegetation slope protection, conducted a field investigation, studied the distribution pattern and density of roots. The law of root density decreasing with increasing soil depth can be drawn.(2) Use the WZL-300 paper tension meter and TGH—2B Universal Testing Machine separately, to test the tensile strength of roots of cynodon dactylon and nerium oleander. The tensile strength of plant roots decreases with the increase of plant root diameter can be drawn.(3) The position of two kinds of plant roots and soil is tilt, horizontal, vertical, intersection, mixing five different forms for the first time. Use the GDS triaxial testing system, study the law of how different layout of roots effects on soil strength. Strain relationship and shear strength parameters are obtained.(4) Comparison of the stress-strain relationship, found that reinforcement effect of cynodon dactylon roots can play only when the strain reaches a certain level (> 2%) play, and nerium oleander roots can play when strain is very small. The two different types of roots have different strengthening mechanism.(5) Comparison of the shear strength parameters of prime soil and add root soil, the presence of roots can enhance soil strength can be drawn. Further, according to the degree of different arrangement of roots enhancing on soil strength, the order of big to small is mixed-place> intersect place> vertically> horizontally> inclined position.(6) Compared with the roots of two plants cynodon dactylon and nerium oleander enhancing the soil strength, study how different types of roots increase the soil strength. Cynodon dactylon roots increasing soil shear strength is reflected in the increase of soil cohesion, and has little effect on the internal friction angle. However, nerium oleander roots increasing soil shear strength is reflected in increase of soil cohesion and internal friction angle, and its ability to enhance soil strength is greater than the cynodon dactylon roots.