Study On The Current Situation Of Sand Disaster And The Effect Of Sand Control Measures In Zhongzaohuo Section Of Golmud-korla Railway

The total length of the new railway from Golmud to Korla is 1215 km.The railway line crosses Taklimakan Desert,Kumukuri desert and Kumtag Desert.There are many types of sandstorm along the line and the wind power is sufficient,so the line is seriously affected by wind-sand disaster.Among them,as a typical sand damage section,the Zhongzaohuo section of Golmud-Korla railway has the characteristics of large wind speed,stable wind direction,long sand storm period.There are a large number of mobile sand dunes are distributed along the line.Under the condition of strong wind,it is prone to form wind sand flow.As a result,the railway line will be eroded by wind and sand,the normal operation of the train will also be affected.Based on the research project of wind-sand flow along the whole line of the newly-built railway from Golmud to Korla,this paper makes a detailed investigation and observation on the current situation of wind-sand disaster in Zhongzaohuo.Therefore,we set up the observation meteorological station of sandstorm,draw the thematic map of aeolian landform,and measure sand dune with three-dimensional laser scanner.In order to study the protective effect of the windblown sand protection measures,we carry out field experiments and use computer to make numerical simulation.By these means,we hope to provide a scientific basis for the prevention and control of wind-sand disasters.After comprehensive analysis,the main conclusions of this paper are as follows:(1)The Zhongzaohuo section of Golmud-Korla railway is seriously affected by sandstorm.Through the establishment of wind sand environment meteorological station in Zhongzaohuo experiment section and draw the thematic map of sandstorm landform,we find that the sand sources in this area are sand and mobile sand dunes.The sand area is widely distributed.Mobile sand dunes are large in volume,large in number and concentrated in distribution and they are close to the railway line.The wind energy in this area is sufficient,and the direction of sediment transport is stable.The synthetic sediment transport direction is 102 °-106 ° and the annual sediment transport potential is 452.1VU,which is a high wind energy environment.In this area,the aeolian sand flow is in the unsaturated transport state,which has a strong transport capacity and is easy to cause the railway sand damage.(2)In this paper,four typical mobile sand dunes around the railway line have been measured twice by three-dimensional laser scanner.After drawing the dune shape by software,it is found that the sand dunes along the railway in Zhongzaohuo area are mainly crescent mobile sand dunes,after the wind season,the volume of dune has increased,and the shape shows regular changes.By calculation,the moving speed of sand dune is 2.92-8.39m/a.Along the synthetic wind direction,the annual sediment transport of small sand dunes is more than 5 tons,that of medium sand dunes is more than 20 tons,and that of large sand dunes is more than 25 tons.The transport capacity of mobile sand dunes is very significant,and the regional sand damage is serious,so corresponding protective measures should be arranged.(3)The existing sand control system in the area of Zhongzaohuo takes the sand barrier with two rows of 2m high and 50% porosity of galvanized perforated mesh plate as the sand control measure,and takes the grass grid strip as the sand fixation measure.In this paper,multi gradient anemometer and portable sand collector are used to study the effect of sand and wind protection.It is found that the maximum efficiency value of sand and wind protection of double row perforated screen appears at 1 m behind the first sand barrier.Under the strong wind environment,the efficiency of wind protection at 0.2 m height can reach more than 90%.After passing through one sand barrier,the sediment transport capacity declines by more than 30%.After passing through two sand barriers,the sediment transport capacity declines by more than 50%.The results of particle size analysis show that the average particle size of the surface particles is reduced by 59.4% after being blocked by the double row perforated screen,and the sand on both sides of the subgrade and in the track is mainly very fine sand and fine sand.(4)Based on the parameters and results of field observation,a sand flow model in the middle fire area is established,and the wind prevention mechanism of the perforated screen sand barrier is studied.It is concluded that the wind prevention efficiency of the double row perforated screen sand barrier is more than 80% in the strong wind environment(the initial wind speed is 12m/s)within 30 m after the two sand barriers.In the extreme wind energy environment(initial wind speed 24m/s),the wind speed within 21 m after the double sand barrier is lower than the wind speed of sand rising,and the wind speed within 38 m after the three sand barriers is lower than the wind speed of sand rising.