Study Of Sand Damage In Culverts And Mechanism Of Sand Blocking In New Sand Barrier Network Of Geku Railway

This paper takes the newly built Geku Railway as the research background.In order to research the basic characteristics of wind-sand flow along the Geku Railway,field survey and sand flow monitoring was dong.Combining with FLUENT software,numerical simulation of culvert sand damage along the Geku Railway and the mechanism of traditional sand-retaining dike were carried out.Based on the results of numerical simulation,a new type of composite sand barrier with high levee net was proposed in this paper.And Parameter optimization of the proposed new sand control measures was determined.The optimum parameters of wind-proof and sand-blocking are obtained.These achievements will have important practical significance for wind and sand control of the desert railway.The main research results are as follows:(1)Through the monitoring and analysis of wind speed and direction along the Geku railway,the monsoon season along the Geku Railway is February to July.During this period,the wind speed shows the characteristics of high sand frequency,high wind speed,high wind frequency and serious wind-sand flow harm.The frequency of different wind directions is analyzed.The dominant wind direction is WNW,the secondary dominant wind direction is W,and the third dominant wind direction is NW.(2)The frequency and roundness of particle size distribution and particle size morphology of collected near-surface sand particles were analyzed.The distribution of sand particle size in near-surface wind-sand flow approximates normal distribution.The particle size with the largest content ranges from 220 to 320 ?m.The range of particle size corresponding to the peak position of particle size is 100-500 ?m.At the same time,the analysis of particle size distribution provided a basis for the size of sand particles in the finite element model.This indicates that most of the grain classification in the field belongs to medium and fine sand.Through roundness analysis,it is found that most of the sand grains in this area are in sub-circle,circle and polar circle states.(3)A three-dimensional model of roadbed-culvert is established based on the practical engineering on site.The flow field analysis and sediment accumulation law of the threedimensional model of roadbed-culvert were studied.Through flow field analysis,the zone of wind speed on the outer and law of wind speed profile in culvert body of middle axes were studied.By studying the regularity of sand heap subgrade culvert,It is found that the orthogonal wind is one of the reasons for the large amount of sand accumulation on the leeward side of the roadbed-culvert structure while Oblique wind is the most important cause of sand in culvert body and End wall area.(4)In this paper,the mechanism of wind-blocking and sand-blocking of traditional sand-blocking dikes was simulated.The velocity variation trend of wind-sand flow passing through sand barrier was analyzed in depth.The velocity zoning of airflow passing through sand barrier was summarized.Based on the results of velocity zoning around the retaining dike and the failure process of traditional sand-retaining dike was clarified.Combining with the field test of sand-blocking law of sand-blocking dike,effective Protective Distance of Sand Retaining Dike were verified.These results provide references for the proposal of new sand control measures.(5)Based on the study of traditional sand barriers,a new type of composite sand barrier with high levee net was proposed in this paper.The new type of composite sand barrier with high levee net is composed of sand retaining dike and HDPE board which is placed at the top of the sand barrier.In this paper,two-dimensional models of HDPE plates with different porosity and height are established.Taking effective protection distance and sand control effect as the evaluation index of wind and sand control performance,the porosity and height of new sand control measures were studied,and the optimum parameters for field application were determined.These achievements provides certain theoretical support for the wind and sand control project of Geku Railway.