| In the process of production and construction of Expressway Slope in loess landform area,soil erosion was serious,which ha d a great impact on the ecological environment and restricts the sustainable development of the ecosystem.The proces s of soil erosion of loess landform was complex and diverse,and the benefits of different soil and water conservation measures in highway slope were quite different.In order to summarize the law of soil and water loss of highway slope in different landform type areas and correctly understand the benefits of soil and water conservation of highway slope,this paper can take the highways in typical landform type areas of Shanxi Province as the research object The USLE and runoff plot observation were used to co mpare and analyze the soil and water loss laws of Expressway Slopes in different geomorphic areas before and after highway construction.Based on the two functions of protecting soil and water resources and improving ecological environment,the soil and wate r conservation effects of different geomorphic areas were quantitatively evaluated,so as to provide reference for Highway Soil and water conservation work in the same geomorphic areas.The main results of this paper were as follows:(1)According to the geomorp hic index<20,20-25,25-30,30-40 and 40-50,the four expressways are divided into plain,platform,hill,small undulating mountain and medium undulating mountain.The relationship between slope area(y)and land acquisition area(x 1),surface roughness(x 2)and cutting depth(x 3)is as follows:Y=-13515.18+21.27×X1-50913.69×X2+1380.76×X3+10076.77×X12-19.69×X1×X2+21.56×X1×X3+37766.45×X22-1570.52×X2×X3+7.85×X32.Itprovidesa reference for the estimation of Slope Area and earthwork volume in the stage of highway planning.(2)The average annual precipitation in the study area in 2013 and 2017 was511.29 mm and 507.39mm respectively.The maximum erosional force of Datong to Hunyuan expressway slope was 877.5 MJ·mm/(hm2·h·a),and the minimum erosional force is 741.8 MJ·mm/(hm2·h·a).The highest and lowest rainfall erosivity were1916.8MJ·mm/(hm2·h·a)and 1832.4MJ·mm/(hm2·h·a)along the highway from Huozhou to Yongheguan.The highest and lowest rainfall erosivity were1998.1MJ·mm/(hm2·h·a)and 1404.0MJ·mm/(hm2·h·a)along the expressway from Pingding to Yangqu.The highest and lowest rainfall erosivity along the expressway from Shenchi to Hequ were 1259.2MJ·mm/(hm2·h·a)and 1160.4MJ·mm/(hm2·h·a).The soil erodibilit y factor in the project area was between 0.1-0.3,and the average slope length factor was 0.34.The average scores of slope factors under the slope conditions of 1:1.5,1:0.75 and 1:0.125 were 7.35,16.95 and 20.1.(3)The slope ratio with the highest freque ncy is 1:0.75 and 1:1.5 respectivel y.There are 7 types of soil and water conservation measures with high frequency:fac ing wall+plant protection,filling slope plant protection,cutting slope plant protection,filling slope arch frame+plant protection,full face wall,mortar rubble slope protection,rubble slope protection.The largest area of highway slope in plain area is filled slope arch frame+plant protection measures(1:1.5).T he largest implementation area of other geomorphic types is the application of f acing wall+plant protection(1:0.75).The vegetation protection area of highway slope in plain area accounts for 70.9%of the total slope area,which is significantly higher than that in other geomorphic areas.The proportion of vegetation protection area in the total slope area of small and medium undulating mountain highway is 50%-55%,which is significantly higher than 31.2%in hilly area.The average soil erosion modulus of Expressway Slopes in platform area,plain area,hilly area,small undulating moun tain area and medium undulating mountain area after construction were 1857.85t/(km2·a),2157.64t/(km2·a),1950.41t/(km2·a),1629.84t/(km2·a)and2433.24t/(km2·a),respectively,which decreased by 76.1%,75.6%,62.6%,74.8%and65.0%.This shows that the eff ect of soil erosion control in plain area and platform area is the most significant.After the completion of highway construction,the total area of average soil erosion modulus<1000t/(km2·a)and 1000?2000 t/(km2·a)in different geomorphic areas accounted for about 50%,and the area of average soil erosion modulus>3000 t/(km2·a)accounted for less than 5%.(4)There was no significant difference in soil bulk density among the seven soil and water conservation measures.The contents of N,P,K and organic m atter of slope soil in different geomorphic areas increased before and after the construction,and the increase of N and P in the area treated with arch skeleton and plant protection measures was significantly higher than that in other areas.The soil K and organic matter increased greatly in the plot treated by plant protection measures.The average value of water and soil resources protected by the seven soil and water conservation measures is 2.2377 million yuan.The total value of arch frame+plant protect ion treatment is the largest,which is 4.2753 million yuan/km2,significantly higher than other treatments.(5)The average total value of water and soil conservation measures is 2.91yuan/km2.The largest is I measure,7.58yuan/m2,significantly higher tha n other treatments.In terms of input-output ratio,the return rates of plant protection measures and full face wall measures are 23.76%and 21.83%respectively,which are significantly higher than other measures.In the future engineering design,it is suggested to optimize the highway slope measures in combination with the engineering design and slope characteristics,and give priority to two kinds of soil and water conservation protection measures:filling slope Arch frame+plant protection measures and facing wall+plant protection measures.This study aims to play the positive role of soil and water conservation measures in protecting water and soil resources and improv e ecological benefits. |
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