Study On Soil Erosion Rules And Soil And Water Conservation Measures Along Expressway From Tongxin To Guyuan

In order to make a study of Rules of soil erosion in the process of expressway construction and have a definite object in view to adopt appropriate soil and water conservation measure system, this study takes expressway soil erosion as research object and chooses the expressway from Tongxin to Guyuan situated in nouth region of Ningxia provinces as an example to analyse expressway soil erosion characteristic and influencing factor, impact of expressway soil erosion on ecological environment and Rules of soil erosion occur and development in side slope of expressway.According to the research soil and water conservation comprehensive measures system of expressway is raised and it contributes to distribution of soil and water conservation measures of similar expressway as a reference. The mostly conclusion is as below:(1) Expressway soil erosion is different from conventional soil erosion and other soil erosion of exploitation construction project for its 4 outstanding features, including imbalance of soil erosion distribution in time and space; Presenting either threadiness or pinnate distribution in space; The quantity of soil erosion is large; Erosion form is complicated and frequency of causality soil erosion occuring is large.The intensity of everage slope soil erosion of all expressway route from Tongxin to Guyuan are 76200.08 t/km².a and 91581.10t/km².a,largely ahead of everage soil erosion of all Ningxia proncince.Expressway soil erosion forms are mostly water erosion and wind-blown erosion and the difference of gravity erosion. wind-blown erosion occurs mainly from Januaryto May, and water erosion occurs mainly from Juneto Serptember.(2) Soil wind-blown erosion of expressway slope in the research district is influenced mainly by soil water amount and soil and water conservation engineering measures and wind factors. When slopes type and soil and water conservation engineering measures are same, soil water amount can reduce wind-blown erosion of slope in some extent; soil and water conservation engineering measures can reduce obviously wind-blown erosion of slope. preventing wind-blown effect of hexagon brick was the best, the second was arch frame-saw, preventing wind-blown effect of mechanical press was worst. Amount of slope wind-blown erosion is influenced by wind speed and wind duration. Althrough analyzing the data of everage wind-blown erosion intensity and wind speed the regression equations are as the following:Q = Kln(V)-P(3) The main fators influending slpoe soil.surface erosion are rainfall amount and rainfall intensity, and there is a notable positive correlation betwween them. Regression equations can be drawn for soilerosion amount (Y) and rainfall amount X₁ and rainfall intensity X₂ .The regression equations are as the following:Dunping ground I Y = 0.239X₁ + 0.101X₂ - 0.255Dumping ground II Y = 0.276X₁ + 0.072X₂ - 0.254Embankment slope III Y = 0.260X₁, + 0.080X₂ - 0.255Embankment slope IV Y = 0.263X₁, + 0.128X₂ - 0.252Embankment slope V Y = 0.273X₁, + 0.128X₂ - 0.250Embankment slope VI Y = 0.239X₁ + 0.101X₂ -0.255There is a negative correlation betwween soil surface erosion and the soil pores density. There is the affinity between runoff of slope and soil granule. When gravel concentration in soil is less than 30% there is a negative correlation between gravel concentration and amount of surface erosion. Grey correlation density between soil surface status parameters and amount of soil surface erosion are all big, and more than 0.6. The smallist amount is 0.6044, and the biggest amount is 0.7311. In a word soil surface status parameters influence obviously the amount of soil surface erosion.Vegetation plays an important role in reducing soil erosion amount. With vegetation degree of conver increasing amount of surface erosion are reducing. In research expressway four kinds of mix-seeding vegetation showed a remarkable impact on soil erosion. Amount of surface erosion of Ammopiptanthus mongolicus+ Agropyron cristatum+ Medicago sativa are at least, the second are Caragana korshinskii + Medicago sativa+ Amorpha fruticosa, the third are Caragana korshinskii+ Nitraria+ Medicago sativa, that of Nitraria+ Ammopiptanthus mongolicus+ Medicago sativa are maximum.(4) With the development of erosion gully, the ratio of small gully erosion amount to all slope gully erosion amount is reducing, and the ratio of middle erosion gully and big erosion gully is increasing. There is no correlation between amount of gully erosion and rainfall, and there is a correlation between amount of gully erosion and everage rainfall intensity. Measure of hexagon brick can prevent the occurrence of slope gully erosion, and arch frame-saw can control effectly the development of slope gully erosion. The effect is best when hexagon brick or arch frame-saw combining vegetation measure. The erosion gully on the dumping ground have a large development.(5) The controlling Measures Along Expressway soil erosion shoule be arranged in accordance with Rules of occuring and development of expressway soil erosion. Measures layout of expressway soil and water conservation should be integrated by "point, line and sheet" to control soil erosion and improve ecological environment along the expressway should be carried out throughly in arranging all kinds of soil and water conservation measures.Measure system of soil and water conservation include preventive measures, interim means, engineering measures and vegetable measure so that guiding principle of soil and water conservation can be carried out of" prevention first, overall planning, integrated control, adjusting measures to local conditions, strengthening management, laying stress on efficiency".According to the characteristic of expressway soil erosion in the research district measures of slope soil and water conservation include the main section of expressway and dumping ground and section of wind-blown erosion.