| Vegetation-slope system is a complex dynamic system,and the influence of plant root system on slope is various.Generally,it can be divided into three types: mechanical effect,hydrological effect and biological effect.The mechanical effects include the reinforcement of shallow root,the traction of lateral root and the anchorage of primary root.Hydrological effects include the interception and reduction of pore water pressure.Biological effects include biochemical interaction with soil substances,increasing the cohesion and friction of soil and improving the stability of shallow landslides.In this paper,the ecological slope of a highway in Zhang Jiakou area was taken as the object of research.In order to study he effect of root morphology on shallow stability of slope,the mechanical effect of bristle grass' s root soil fixation on slope protection was studied.The main root forms were loose root system,horizontal root system,vertical root system,inclined root system and mixed root system.Through the direct shear test of different moisture content,root content and root morphological distribution,the root morphological distribution with the greatest increase in strength was obtained.On this basis,the stability of the bare soil and vegetation soil under this morphology was calculated.The influence of this distribution morphology on the slope stability was obtained.The experimental results of different patterns of root system distribution follows:1.The shear strength envelope obtained by fitting is nearly parallel,which indicates that the shear strength index of root-soil complex is mainly reflected in the change of cohesion.The reinforcement effect formula of root-soil complex with different root distribution patterns were obtained by fitting the cohesion.Cohesion is proportional to the root content and linear relationship and inversely proportional to the logarithm of water content.Different root distribution have different levels of increasing in shear strength,so the influence of shear strength index is different.The shear strength is plain soil,horizontal root system,loose root system,vertical root system,inclined root system and mixed root system from small to large.2.The stability of slope is greatly influenced by shear strength.It can be concluded that the distribution of mixed roots has the greatest influence on the stability of the slope.Through the calculation of different shallow slope stability formulas,it can be concluded that the main reason of slope instability lies in the existence of weak surface in the slope,which reduces the stability of the slope.Ecological slope stability methods ? is obtained by using the model of infinite slope.It divides into two conditions,the one is that the root system passes through the critical slip surface and the other is that the root system is above the critical slip surface.Although the root system is above the critical slip surface,there is no root system passes through the critical slip surface.If the influence of the root system is taken into account,the stability of the slope will be increased.When other conditions are the same,the greater the slope is,the smaller the safety factor is,the more likely to instability.According to the method of stability analysis of ecological slope II,the stability of the slope is negatively correlated with the slope's angle,the depth of the slip surface,and the width of the slip surface.The stability of the slope is positively correlated with the ratio of the width of the sliding body.With the increase of the slope's angle,the safety coefficient of the sliding body depth and width decreases.With the increase of width-length ratio of sliding body,the stability of slope increases.The slope safety factor decreases significantly within the range of 16% to 18% of water content,indicating that the slope is significantly affected by the change of water content in this interval.Slope stability changes significantly in the range of slope gradient from 21 to 27 degrees,depth from 0.5m to 1m and sliding body width 4m to 6m,which has great influence on slope stability.On the contrary,the width-length ratio has little influence. |
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