Study On Sand Accumulation Rule Of Desert Highway Roadbed And Road Surface And Sand Transport Subgrade Structure

With the development of society and economy,the demand of modern traffic construction in southern Xinjiang is increasing,and the pace of highway construction is accelerating.However,highway construction in southern Xinjiang is often faced with special environmental problems of crossing the desert or building on the edge of the desert.In this environment,the phenomenon of wind-sand flow is frequent,which makes the roadbed of the desert highway affected by wind erosion and sand burial,and affects the driving safety.Therefore,it is necessary to take some measures to prevent the damage of wind sand flow to the desert highway in southern Xinjiang.Traditional sand control measures are mainly "strong resistance and strengthening" by setting sand barriers,but there is a lack of scientific research on improving the sand transport capacity of subgrade by designing reasonable subgrade section parameters.This study takes the38 th Corp-Tazhong(proposed),Yuli-Qiemo(newly built)and Tumushuke-Kunyu(proposed)desert highway as the object of investigation.Based on the atmospheric reanalysis data of ERA5,the value range of wind direction and wind speed in the numerical simulation is obtained,and the characteristics of sand flow field and sand accumulation distribution of different subgrade sections are further explored.The geometric parameters of subgrade section are optimized by Design Exploration optimization analysis method,and the main conclusions are as follows:(1)The subgrade sections of the highway in the southern Xinjiang desert are mainly embankment and cut subgrade,and some sections have semi-fill and cut subgrade.The dominant wind direction of the three highways is east-northeast(ENE),northeast(NE)and East(E)respectively,and the Angle of the direction of the highway is within 60°～90°.The annual average wind speed is 6 m/s,and the maximum wind speed is 15m/s.The particle size of the sand in the project area is distributed in the range of 0.10～0.25 mm.(2)The distribution of wind velocity flow field and sediment accumulation in different subgrade sections is basically the same.When the airflow passes over the road shoulder,the wind speed increases and wind erosion is easy to occur.There is a deceleration phenomenon at the foot of slope,and the distribution range of sand accumulation is large,which is easy to produce sand burial.The higher the height of filling and excavation,the steeper the slope,and the more vertical the Angle between incoming flow and subgrade strike,the more serious the damage of sand burial and wind erosion.(3)The parameters of sediment transport section are different for different incoming wind speed and subgrade strike.For the embankment section,when the Angle between the incoming flow direction and the strike of the embankment is 60°,the corresponding embankment section parameters of the incoming flow wind speed of 15 m/s are as follows: embankment height of 1.5 m and embankment slope of 21.7°.When the Angle between the incoming flow and the embankment is 90°,the section parameters of the sand transport embankment corresponding to the incoming flow wind speed of 15 m/s are the embankment height of 1.0 m and the embankment slope of 23.1°,and the section parameters of the incoming flow wind speed of 9 m/s are the embankment height of 0.8 m and the embankment slope of 24.5°.For the cutting section,when the Angle between the incoming flow direction and the cutting strike is 60°,and the incoming flow wind speed is 15 m/s,the corresponding cutting section parameters are as follows: the depth of the cutting is 1.2 m,and the slope of the cutting is 23.4°.When the Angle between the incoming flow direction and the strike of the cut is 90°,the section parameters of the sand transport cut corresponding to the incoming flow wind speed of 15 m/s are as follows: the depth of the cut is 1.0 m and the slope of the embankment is 20.38°;the section parameters of the sand transport cut corresponding to the incoming flow wind speed of 9 m/s are as follows:the depth of the cut is 0.6 m and the slope of the cut is 26.0°.(4)The sediment transport capacity of different subgrade sections is different.The sand transport performance of semi-filled downslope flow subgrade is the best,that of embankment subgrade is the second,and that of semi-filled upslope flow subgrade is the worst.Therefore,the semi-filled downslope flow subgrade should be preferred in the areas with large relief,the embankment section should be preferred in the areas with little relief,and the semi-filled upslope flow subgrade should be avoided on desert highways.The objects investigated in this thesis are representative in southern Xinjiang,and the research results can provide theoretical basis for the selection of subgrade section type and subgrade section parameter design of desert highway in southern Xinjiang,and have certain guiding significance for similar highway construction.