Study On Development And Mechanism Of Water Erosion And Ecological Water Erosion Control Technology Of Highway Slope In Cold Region

It is very important to prevent soil erosion and strengthen ecological protection on expressway embankment sideslopes in the Qinghai-Tibet plateau of China,which directly threaten national ecological barriers and optimize the technology level of highway slope protection of our country.In this study,three of typical highway slope in the Qinghai-Tibet plateau and Qinghai-Tibet engineering corridor?along the Qinghai-Tibet highway on both sides of the range of 48km2?were selected as the research object,methods of combining with the RUSLE model based on GIS technology and ¹³⁷ Cs radionuclide tracing technique,field investigation and scouring experiment,which were conducted to investigate soil erosion characteristics and process and mechanism.The erosion intensity characteristics and influencing factors of erosion of the Qinghai-Tibet engineering corridor was clarified,the soil erosion characteristics and mechanism and its effects on highway slope in cold region was analyzed.The gully development process of bare slopes was revealed,the soil erosion characteristics and its mechanism of erosion of highway slope with two common plant protection measures such as Transplanting turf and three-dimensional net seeding on the Qinghai-Tibet Plateau were studied,the strategy of ecological protection of highway slope in cold and high altitude regions was stated.Which will be provide scientific basis for the ecological protection and ecological restoration of highway construction in the Qinghai Tibet plateau,and also provide scientific guidance for the development of the soil erosion prediction model of Qinghai-Tibetan Plateau.The main results were as follows:?1?The characteristics of soil erosion and the relationship between the factors and erosion intensity in the region of the Qinghai-Tibet engineering corridor were clarified.The soil erosion intensity in the area of the Qinghai Tibet engineering corridor was slightly and micro-degree dominated?first and second gradation of Chinese classification?,and the proportion of the two kinds of erosion intensity was more than 60%,the proportion of erosion intensity under Moderate?third gradation of Chinese classification?was 78.94%.The erosion intensity and ¹³⁷ Cs content were significantly related to land use types,soil erosion intensity and ¹³⁷ Cs content with different land use types as the order is forest land,grassland,farmland,roadside bare sand,grass,as for grassland types showed large difference,followed by the desert grassland,alpine meadow grassland,alpine grassland.The R value ranges from 16-2037.03 MJ·mm/hm2·h·a,showing an overall increasing trend from the southern to the northern,the K value was in the range of 0.13-0.83 t·hm2·h/hm2·MJ·mm,the cumulative area the regions' LS value less than 5 is about 46%.The C value at the southern of ANDUO is Reach 0,and at the northern is tend to 1.The grey correlation degree of R,K,LS,C,P value and A value were 0.677,0.505,0.193,0.627,0.625,respectively.Low coverage of desert grassland and alpine grassland and sandy land and bare land is the main source of roadside erosion zone of Qinghai Tibet engineering corridor.the LS value of The regions is more than 15,which should be avoid future highway construction.The effective method of weakening soil erosion should be to increase vegetation coverage,layout effective measures of soil and water conservation.?2?The soil erosion characteristics and the gully development process on bare slope in cold regions was analyzed.In regards to bare highway slope,the slope runoff increase with flushing time increases,and its change degree was positively correlated to inflow rates.Inflow rates and runoff increased,which greatly increased soil loss.the ratio of the relationship between sediment yield and runoff on bare slope had no correlation,The sediment yield of the bare slope decrease along with the scouring duration.The relationship between the cumulative runoff and the cumulative sediment yield in the bare slope is satisfied with the power function.The main development process of gully erosion on the bare highway slope in cold and high-altitude regions was from sheet erosion to rill erosion and Shallow Gully Erosion,the main erosion type changed from sheet erosion to intensive rill erosion,the degree of gully development and soil erosion intensity on the eastern slope is higher than the western slope.Under the experimental conditions,Bare slope erosion gully average rill width is between 3.63-5.92 cm,with an average depth of the rill between 3.0-6.34 cm,rill erosion average depth is between 1.60-3.34 cm,with total area of the slope rill between 0.62 to 1.30 m2.For the length of 10 m slope,at the length of 1-3m and 7-8m regions is the main part of the gully development and distribution of slope rill erosion,and also is the main site of occurrence and soil loss area.The cumulative length of slope rill erosion,rill average depth increases with inflow rates increase,erosion gully width and depth increase with the inflow rates increases and reach to a certain state,when the slope rill erosion forming,the effect of inflow rates on erosion gradually weakened.The average rill width and depth,the cumulative length and average depth of rill increases with the length of slope first increased and then decreased.?3?The soil erosion characteristics and its benefits of slope with two common plant protection measures such as Transplanting turf and three-dimensional net seeding on the Qinghai-Tibet Plateau were studied,Soil erosion prediction models for seeding measures of highway slope on the Qinghai-Tibet Plateau was established.The vegetation cover can effectively reduce the runoff and sediment yield process,reduce the runoff and sediment yield of the highway slope in the cold and high altitude regions,Inflow rates and vegetation cover significantly affected runoff and sediment yield,and the runoff of the slope had a significant negative correlation with vegetation coverage,runoff erosivity decreased,which greatly decreased soil loss.Soil loss in treatments under 37% cover decreased by 92.6–95.4% compared to soil loss from bare sideslopes.The 37% Elymus dahuricus cover on expressway embankment sideslopes with three-dimensional net seeding was a suitable cover percentage on the Qinghai-Tibet Plateau.sediment on bare slope 9 and 13 times than the sediment on the slope with the coverage of 37% and 74%.Under the experimental conditions,when the inflow rate is 3 L/min,the benefits of Transplanting turf is less than three-dimensional net seeding measures.when the inflow rate is 8 L/min,the benefits of Transplanting turf is better than three-dimensional net seeding measures.The control ability of three-dimensional net seeding measures on sediment yield is better than that of Transplanting turf,and the control ability of three-dimensional net seeding measures on runoff is less than that of Transplanting turf.In the non-full coverage condition,for the different measures,the comprehensive protection benefits order is three-dimensional net seeding is better than part of Transplanting turf,for the different turf pattern,the benefits order is turf in the lower part better than turf at the top part.The effect of sediment retention of slope vegetation measures in cold and high altitude regions are mainly interception coarse sediment.?4?The Hydrodynamic Characteristics and mechanism of the highway slope with bare slope and different measures were analyzed.The Soil denudation rate of bare highway slope has a significant relationship with runoff shear stress,stream power,Unit energy of water-carrying section.The Soil denudation rate showed a quadratic function with unit stream power,show a logarithmic function relationship with Flow kinetic energy.By using the grey correlation analysis of each factor and Soil denudation rate,the order of hydrodynamic parameters is the resistance coefficient,Reynolds number,Froude number,the rank of erosion kinetic parameters is unit stream power,stream power,Flow kinetic energy,Unit energy of water-carrying section.For the different coverage of three-dimensional net seeding measures,Reynolds number and Froude number and the coefficient decrease as the coverage increases,the unit stream power and Flow kinetic energy exponentially decreases with coverage increased.For the different slope protection measures,unit stream power of three-dimensional net seeding measure and Transplanting turf measure show a same benefit than bare slope.For the rank of the unit stream power on three pattern of turf is full turf,in the lower part turf,at the top part turf.makes the emergence of the slope material composition difference,and changes the flow pattern and flow rate and the distribution of energy and power.Due to the turf,the material composition of slope has changed,and also the flow pattern,flow rate,the distribution of energy and power has changed.?5?The ecological protection strategy of highway slope in the cold and high altitude regions was stated.Those strategy include the standard definition and classification of how to choose the road line with the strategy of soil and water conservation,proposed ecological slope protection general requirements and recommendations on Qinghai Tibet Plateau,described the existing ecological protective measures in the key process to reduce soil erosion on the slope,a new slope protection technology named as comprehensive model of turf skeleton measure,focusing on the local species selection,domestication,development and utilization for the highway slope artificial vegetation construction as an important measures of ecological protection in highway in cold and high altitude regions.