| Vegetation maintaining slope stability can effectively overcome the shortcoming of engineering measure maintaining slope stability. When vegetation maintaining slope stability exert the function of soil reinforcement and slope protection of vegetation, at the same time , it can fully exert landscape and environment effects of vegetation. Vegetation maintaining slope stability has the characteristics of lower construction cost ,better controlling effect ,longer work time and satisfying the environmental protection requirement as well. In Dongchuan district with large quantity landslides and landslides widely distributing , vegetation measure is adopted to control surface and shallow landslides,which can achieve the aims of not only controlling landslides but also improving the ecologic environment. It is the first choice to control surface and shallow landslides according to nature ,economy and society in Dongchuan.In Dongchuan xiaojiang river basin ,geological tectonism is violent ,earthquake is frequent, height difference is large ,rock is fragmental , hillslope is steep , stability of hillslope is bad , mountain is unstable ,precipitation is concentrative and rainstorm is frequent .Those nature conditions create the possibility for full development of landslide hazard in Dongchuan xiaojiang river basin . Forest vegetation is severely destroyed during economic construction and smelting copper by felling tree in history , grassland is overload to graze ,waste of mines is arbitrarily piled up and bush grass is artificially destroyed .All of those unreasonable human activities and land-use types accelerate the happening of landslide hazard.Typical sample plats are selected in bare soil,heteropogon contortus grassland,vetchleaf sophara shrub land,witch sorrel shrub land,albizzia land and eucalyptus land. Soil samples come from different soil depth in the scope of root system distributing on selected sample plats . After soil samples are prepared on the design demand of moisture contents, soil samples are directly sheared . Experimental results show that parameter valuation of shear strength of remolded soil samples that come from different vegetation types are decreased as moisture contents is added. Results take on a trend on the whole that parameter valuation of shear strength of remolded soil samples is increased as soil depth is increased . Through relevant analyses between cohesion and moisture contents , between friction angle and moisture contents respectively , it has been found that there is a negative correlation between common logarithm valuation of cohesion and moisture contents and also a negative correlation between natural logarithm valuation of friction angle and moisture contents .Root contents including different diameters of different soil depth from five kinds of vegetation are measured by using selected soil samples that contain root system . Results indicate that gross root content including different diameters of different vegetation types is decreased as soil depth is added and that for root content whose diameter ranges from 0 to 2mm , there is a rule that root system of witch sorrel shrub land > root system of vetchleaf sophara shrub land > root system of heteropogon contortus grassland >root system of albizzia land> root system of eucalyptus land . There is a exponential function relationship between root content whose diameter ranges from 0 to 2mm of different vegetation types including different diameters and soil depth . There is a exponential function relationship or linear relationship between gross root content including different diameters of different vegetation types and soil depth .At the state of natural moisture contents ,vegetation can improve shear strength of soil ,contrasted with bare soil. For added valuation of cohesion and friction angle of soil samples that come from different soil layer and different vegetation types, contrasted with bare soil, there is a rule that soil samples of witch sorrel shrub land > soil samples of vetchleaf sophara shrub land > soil samples of heteropogon contortus grassland > soil samples of albizzia land > soil samples of eucalyptus land . There is a power function relationship between added value of friction angle and soil depth . There is a exponential function relationship between added value of cohesion and soil depth .After soil samples are prepared by altering root contents whose diameter ranges from 0 to 2mm of soil samples that contain root system on the design demand of root contents, soil samples are directly sheared . For different vegetation soil samples that contain root system , both cohesion and friction angle of soil samples are added as root content whose diameter ranges from 0 to 2mm is added . It has been found that there is a power function relationship between common logarithm valuation of cohesion and root content whose diameter ranges from 0 to 2mm and also a power function relationship between natural logarithm valuation of friction angle and root content whose diameter ranges from 0 to 2mm . There is a trend on the whole that added value of cohesion and friction angle of soil samples is added as soil depth is increased. There is a trend on the whole that increasing rate of cohesion and friction angle of soil samples is decreased as soil depth is added .Tensile strength of root system that come from vetchleaf sophara shrub land , witch sorrel shrub land, albizzia land and eucalyptus land in selected sample plats are measured in laboratory . Experimental results show that there is a power function relationship between maximum tensile strength of root system of different vegetation types and diameter of root system . Results also show that there is a positive correlation between maximum tensile force and diameter of root system . Anti-drawing stress of root system come from four kinds of vegetation are directly measured in sample plats. For average anti-drawing stress of root system from different vegetation types, there is a rule that root system of eucalyptus land> root system of albizzia land>root system of witch sorrel shrub land > root system of vetchleaf sophara shrub land . The anchoring effect of root system of eucalyptus land is best . During vegetation maintaining slope stability , internal and external environment condition is varied and anti-slide stress is added in order to maintain stability of slope by root system ,stems and leaves on earth , forest floors and life activity of vegetation itself .Action of soil reinforcement and slope protection include the action of decreasing moisture contents because of rainfall interception of vegetation and water uptaked in plant roots , the action of enhancing shear strength of soil because of decreasing moisture contents and plant roots consolidating and winding soil and the action of enhancing stability of landslope because of enhancing shear strength of soil and anchoring of root system . Improving of shear strength and increasing of anti-slide stress on landslope are in favor of improving the stability of surface and shallow landslide.During engineering design of vegetation maintaining slope stability , landscape effect and function of improving environment should be fully considered after the vegetation engineering is put in practice .When vegetation types of maintaining slope stability are selected , it is demanded that vegetation can meet with protection requirement , on the other hand vegetation can be adapted to habitats of afforestation and cultivating grass ,namely , can satisfy adaptable tree and grass for right soil. Before soil reinforcement and slope protection are put in practice , it is necessary that seeds of seedling are cultivated reasonably ,soil preparation is implemented in appropriate time . In order to improve the capacity of vegetation for soil reinforcement and slope protection , the way of sow seedling should be adopted as soon as possible .After soil reinforcement and slope protection are put in practice, continuous management should be reinforced in order to ensure to exert effectively the function of soil reinforcement and slope protection for a long time.
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