Research On Influences Of Wind-sand Disaster On Railway Transporting And Mechanical Barriers On Protective Effect

The damages of wind and sand always threaten the normal running of the railways in the desert,which makes trains can't run normally and even causes the safe accidents of the trains' s derails and rollover.Besides,great harm for our country's properties and people's lives is brought by the damages of wind and sand.And some of the financial developments and the communications of the culture are also hindered.In order to reduce or avoid the railway damages of the sand and wind,lots of studies have summarized to use “fixing,hindering,running conducting”on the sides of the railways to intervene mechanically and succeeded practicing in real projects,And achieved remarkable results.The present study was stimulated to use FLUENT software to set up Euler-euler Two-fluid flow,the unstable model,which can simulate the figures for wind-sand fields on both the single and the double row mechanical sand barriers and provide theoretical and technological bases for the prevention and cure of railway sand-wind damages and the parameter designs of the second row mechanical sand-wind damages.The present experiment was to answer the following research statements:(1)Deeply understand the impact of wind and sand disasters on the safety of railway transportation,which is mainly reflected in the two categories of embankment wind erosion and sand buried line,and movement characteristics of sand force,wind and sand flow.,as well as the analysis of the stress of sand particles On this basis,build the fluid control equation and the standard k~? equation.(2)The deceleration zone,acceleration zone,and the back flow zone have appeared on the leeward sides of mechanical barriers.Comparing with the single row mechanical barriers,the features of the back flow zones formed by the double row mechanical barriers were significant,and the scopes were large and the intensity was high.Besides,the back flow zones were far away from the foot of windward slope,which didn't make lots of sand accumulate around the foot of the windward slopes.Thus,it reduced the trend that accumulated sand climbed towards the windward slopes and the effects that the double mechanical barriers reduced the flow were better than the sing ones.The doubles ones increased the flow speed above the railway embankments,which caused the sand to obtain more energy in the suspending and it sped to cross the railway embankments and further helped to accumulate the sand along the railways.(3)The space of the 10 H double row mechanical barriers had better effects on the less strength in the wind speed and the sedimentary and greatly improved the protective effects along the railways through the qualitative analysis of the speed field among different spacing double row mechanical barriers and the qualitative analysis of the mechanical barriers on blocking the sand.(4)Through simulating the numbers on the second row sand barriers,the results revealed that the higher the mechanical barriers,the intensity of vortex zones the bigger,the efficiency of the wind reduction the higher,which indicated the sedimentary quantity of sand was caused the enrichment of sand.Among the vortex region scope was small and the intensity was low and even the effects on defensing sand was not enough formed by the sand barriers with the height of 1 m and 1.5 m.However,the higher the sand barriers,the pressure on the sand barriers the bigger,and the more cost was needed.the height of the second sand barriers was advised to be from 2.5 to 3 m.Since the length,height and intensity of the vortex flow narrowed with the increase of the porosity of the second mechanical barriers.At the same height,most sand was not blocked by the mechanical barriers and no significant effects were caused.Although the small porosity could reduce the wind speed behind the sand barriers,the leeward sand was around the mechanical barriers and was easy to be buried.Considering the comprehensive factors,the porosity of the second mechanical barriers was best to be 10 to 20%.Comparing with others,the better reducing effects on the flow would have and the sand quantity involved in the flow would be the least if the tilt angles of the second sand barriers were 120 °.The closer to 0 °the angle,the closer to the foot of windward slope the places where sand accumulated.With the impacts of sand flow,the windward sides of railways would appear corrosion and erosion,which would reduce the stability.The flow would not grind the slops butt it could reduce the quantity of sand blocked by the sand barriers.if the angles approached to 180°.Based on above,the 120° tilt angles were the best choice,because they could not only block the sand but also not corrosion.