| Since the 21st century,more and more attention has been paid to ecological construction and environmental protection.Ecological slope protection technology arises at the historic moment which has been widely used in engineering practice at home and abroad.Due to the unique mechanical,hydrological and biological effects of vegetation,it plays a good role in slope protection for highway and railway slope engineering.Vegetation roots can not only improve the mechanical properties of slope,but also maintain a certain matric suction under the condition of rainfall.It can slow down the infiltration of rainwater and reduce the permeability coefficient of soil,so as to improve the shallow stability of slope.Based on the hydraulic characteristics of vegetation slope protection,this paper studies the vegetation slope protection in Zhangjiakou,aiming to provide theoretical support and technical basis for the application of vegetation slope protection in Zhangjiakou and other similar areas.The following conclusions can be drawn from the research:1.The matric suction and water holding capacity of different types of vegetation soils were studied through indoor rainfall model test by selecting common slope protection vegetation and combination.During the 1-hour rainfall with intensity of159.2 mm/12 h,the matric suction of the soil with mixed vegetation of festuca,the mixed vegetation was higher than that of the bare soil at all depths.After the rainfall,vegetation soil can maintain higher matric suction than bare soil,and the mixed vegetation soil has a relatively significant matric suction maintenance ability.The water holding capacity of vegetation soil is higher than that of bare soil,among which mixed vegetation has better water holding capacity due to developed root system.2.The effect of vegetation root system on soil permeability was studied by combining field double-loop infiltration test with indoor infiltration test.It was found that the root system had a significant effect on reducing water infiltration.For the soil with a root content of 0.82%,the infiltration rate was significantly reduced and the saturation permeability coefficient was the lowest when the root system reached the steady-state seepage because the relatively developed roots occupied more pores in the soil.The saturated permeability coefficient of the root soil complex was lower than that of the bare soil in both remolded soil and undisturbed soil.With the increase of root content,the saturated permeability coefficient of the root soil complex decreased gradually.The vegetation soil with higher root content has more significant effect on reducing water infiltration.3.Based on the actual engineering background of Zhangjiakou,a vegetation slope model was established by using the finite element analysis software MIDAS GTS/NX to study the influence of vegetation on the slope stability under the effect of rainfall.Under the condition of the same rainfall intensity and duration,the infiltration rate of the slope with mixed vegetation of festuca,lobular boxwood and grass irrigation is lower than that of the exposed slope,which has better hydraulic characteristics.After12 h of rainfall,part of matric suction was still maintained in the slope top,slope surface and slope bottom soil,and the pore water pressure and rainfall influence depth at the same height were all lower than those under other conditions.In the analysis of slope stability,the safety coefficient of bare slope is lower than that of three different types of vegetation slope.In the absence of rainfall conditions,the safety coefficient of the lobular boxwood vegetation slope is the highest,and that of the festuca vegetation slope is the highest after 12 h of rainfall conditions.The existence of vegetation roots can effectively slow down the infiltration process of rainfall and improve the stability of slope. |
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