Research On The Characteristics Of Wind And Sand Flow In Railway Embankment And The Effect Of Mechanical Sand Barrier On Wind And Sand Resistance

Wind sand flow will cause two types of sand damage to embankments and track beds,namely wind erosion and sand burial.In order to prevent the embankment slope from being eroded by sand-carrying wind or the surface of the track bed being buried by sand,it is necessary to lay mechanical sand barriers on the windward side of the embankment to weaken the wind.strength to intercept sand accumulation.Based on the fluid mechanics software Fluent,this paper takes the railway embankment,semi-concealed sand barrier and high vertical windbreak and sand retaining wall as the research objects,and uses ICEM to establish a finite element model to study the air flow field around the embankment based on the Lanxin Railway.situation,and the distribution of sand accumulation.By changing the working conditions,the wind and sand blocking effect of each mechanical sand barrier is analyzed,and the simulation results of each chapter are compared with the experimental measurement results of other scholars.The main research contents and achievements are as follows:(1)The migration law of sand particles in the two-phase flow of wind and sand is described mainly in three ways: jump,suspension and creep.The stress of a single sand particle in the air flow field is analyzed,and the influence of sand particles is determined.The main cause of migration is wind.When the wind-sand flow erodes the embankment,the characteristics of the wind velocity and flow field around the embankment are divided into: deceleration area at the foot of the windward slope,superposition area on the windward slope,surge area on the shoulder of the windward slope,high-speed area at the top of the embankment,deceleration area on the leeward slope,and vortex area at the foot of the leeward slope.And the wind speed recovery area behind the embankment.Finally,the variation trend of the horizontal and vertical profiles of wind speed is compared with the measured results to verify the validity of the calculation model.(2)The wind-proof effect,sand-blocking effect and sand-blocking principle of the semi-concealed sand barrier were studied,and a numerical model of the semi-concealed checkered sand barrier was constructed to explore the wind-sand flow formed by the sand shape in the concave and curved area of the checkered sand barrier.The field process and the characteristics of the air flow field on the surface of the sand barrier are analyzed,and finally the validity of the simulation results is verified.The conclusion drawn from the simulation of the semi-concealed sand barrier is that the sand barrier is suitable to be arranged in areas with low wind speed,and mainly plays the role of isolating wind and sand flow in the near-surface range,and the roughness of the sand barrier is proportional to its protective effect.,when the wind speed is greater than 20m/s,the increase of roughness cannot greatly improve the sand blocking effect and it is easy to be buried by strong wind sand and quicksand.(3)The wind and sand blocking effects of high vertical wind and sand-retaining walls are analyzed under different wind speed conditions when they are arranged at different positions.,the sand blocking effect is to analyze the thickness of sand accumulation at each characteristic point of the embankment and the distribution range of sand phase volume fraction as evaluation factors after the wind-sand flow is stable.Finally,the simulation results of this chapter are compared with the measured results of other scholars to verify the validity of the model.(4)Summarized the protective effects of two kinds of mechanical sand barriers,expounded the wind and sand blocking effects of semi-concealed sand barriers and high vertical wind and sand barriers under different wind speed conditions,and concluded that:semi-covert sand barriers It has good sand blocking effect in areas with low average wind speed,but its windproof effect is poor and cannot effectively prevent wind erosion of embankment.The high vertical sand retaining wall can effectively make up for the problem of the semi-concealed sand barrier being buried in the sand under strong wind,and in order to maximize the economic benefits of the high vertical sand retaining wall,it is necessary to arrange the wall reasonably according to the prevailing wind speed of the year.s position.