Research On The Mechanical Behavior Of Sand-Proof Facilities And Engineering Applications

In the wind and sand environment,the desert railways are vulnerable to the disasters of wind and sand during the operation.In order to maintain the normal operation safety of the railway,it is particularly important to set up sand-proof facilities.According to the wind load of the sand-proof facilities in the actual wind field,the calculation formula of the sand-bearing wind was derived.Based on an effectively new sand-proof butterfly porous fence which was proposed in the previous period,the mechanical properties and surrounding flow field characteristics of different forms of sand-proof facilities(sand retaining wall,upright wind-sand barrier,butterfly porous fence with uneven porosity)under wind and sand conditions was studied by the FLUENT,and the accuracy and rationality of the numerical calculation model were verified by tunnel experiment.In addition,combined with the environmental conditions along the desert railway in Qinghai Yadan landform area,the sand-fixing bricks were designed as sand-fixing barriers on the near-railway side to form a comprehensive wind-proof and sand-fixing system.Through the comparative study of the wind-sand prevention and treatment system on the flow field characteristics,the wind and sand-fixing effect was evaluated.And the conclusion are follows:(1)Established a calculation model for the sand-bearing wind load of the sand-proof facilities,and derived the calculation formula for the sand-bearing wind load;According to its height setting,consolidation method of the butterfly porous fence,and considering the factor such as wind-induced vibration response and structural dynamic amplification response in the actual sand flow field,The correction coefficient of sand-bearing wind load was derived which were suitable for the sand-proof facilities with two ends fixed and 2m height.(2)The FLUENT was used to establish the fluid-solid coupling calculation model of the sand-proof facilities.After the accuracy and validity of the model were verified by the model experiment,the mechanical behavior analysis of the three sand-proof facilities was carried out.The wind load received by the three types increased quadratically,and the wind load of the butterfly porous fence was reduced by 22.3% compared with the upright wind-sand barrier,and the maximum was 47.2%lower than sand retaining wall.Compared to the other two forms,the butterfly porous fence was subjected to the least wind load.(3)Static analysis of sand-proof facilities,with the increase of velocity,butterfly porous fence had better overall strength,wind resistance and stability.The mechanical properties of butterfly porous fence with different thicknesses under strong wind conditions were analyzed,and the fitting formulas of thickness and wind speed were derived.The thickness of fences in different environments could be reasonably selected to improve economic benefits.According to the turbulent energy and pressure distribution behind the sand-proof facilities,the reason for the smaller force of the butterfly porous fence was obtained.(4)According to the actual investigation on the Yadan landform area in Qinghai,according to the subject,the wind-sand prevention and treatment system of butterfly porous fence and sand-fixing bricks was designed.For sand-fixing bricks,when the height was 40 cm,the porosity was 5%,and the laying was 1m×1m square,the maximum velocity in the bricks was reduced by 93.3%,the trend of turbulent kinetic energy in the sand-fixing area was basically similarity,with little air disturbance,and a well vortex could be formed,which improves the protective effect and increases the shielding distance.(5)Through the wind-sand prevention and treatment system combined with three sand-proof facilities and sand-fixing bricks barriers,the characteristics of the flow field were compared and analyzed.When the butterfly porous fence was applied to the wind-sand prevention and treatment system,the velocity reduction effect and the shielding effect were significant,most of the sand was deposited in the sand-fixing area,avoiding the wind erosion and sand sand burial.The protective effect on the flow field was mainly concentrated within the height of the fence.The flow field around the embankment was relatively stable,ensuring the formation of safety.