Study On The Benefit Characteristics And Configuration Optimization Of Nylon Sand-fixing And Sand-resisting Barrier Protection

Sand-fixing and Sand-resisting barriers are widely used in the protection of wind-blown sand disasters in linear projects,their layout mode directly affects the efficiency and cost-effectiveness of wind and sand prevention in protective engineering.On the windward side of the sand-crossing highway in Ulan Buh Desert,a nylon net sand barrier with sparse top and dense bottom was installed.Through the field control contrast test as the main means and the indoor wind tunnel test as the auxiliary,the actual wind-proof and sand-fixing and sand-blocking characteristics of Sand-fixing and Sand-resisting barriers at different distances,heights,specifications and combinations were observed.The results show that:(1)As the specification of sand-fixing barrier is larger,,the fluctuation range of wind speed decreases,the overall protection benefit in the barrier becomes worse,and the fragmentation of wind speed in the buffer area becomes more dispersed.As the height of sand-fixing barrier increases,the range of sustained deceleration and the position of V-shaped fluctuation become more backward,and the inflection point of rapid reduction of wind speed rises.The cross-sectional area of low wind speed area becomes larger and more stable,and the buffer zone of longitudinal section becomes shorter.The effect on the enhancement of the height protection effect is gradually greater than that of the side length specification.The sand material in the sand barrier observation site is mainly deposited in the 0-15 cm height layer.With the increase of the specification,the sediment transport in each height layer increases,the stability of the sand surface becomes worse,and the erosion between barriers deepens.The accumulated sand thickness is fitted with the horizontal distance in a quadratic function,and the higher the height,the lower the sediment transport flux in the site.The sand retention rate gradually increases from windward side to leeward side,and the average retention rates in front,middle and rear of the observation site are 37.90%,89.51% and 98.62% respectively.(2)As the distance between sand barriers is larger,the long tail of overall wind speed frequency is farther to the left,and the fluctuation shape of acceleration rate of single-row sand barriers is generally V-shaped and double-row W-shaped.Within the height of0-50 cm near the surface,the greater the height of the sand barrier,the better the wind-proof effect,and the protection benefit in the middle of the sand barrier is significantly affected by the spacing.The area where wind speed is significantly reduced by single-line sand barrier is basically at-2H-3H.Double sand barriers can form a continuous and stable weak wind area at 4H interval,the protective effect extends obviously at 8H interval,and the protective belt is discontinuous at 12 H interval.Sand transport by sand barrier is mainly concentrated in 20 cm,and the average interception rate of sand barrier is 85.14% at 3H after single sand barrier,91.23% at 5H after barrier,and 93.53% at 3H after double sand barrier.Double-row sand barrier has a high sand blocking ability.With the increase of the spacing,the heights of the highest point,the second highest point and the lowest point between barriers decrease.The differences of the highest point of sand accumulation under the three spacing are 5.9cm and 8.7cm,and the fitting of the height and distance of sand accumulation between barriers accords with the quadratic function of one variable.(3)On the premise of achieving the same excellent protection ability,When the sand barrier protection project is laid in the area with medium and low wind energy(< 12m/s),The optimal sand barrier configuration is 0.8-1.0 m height and 8H spacing,which can save 2.85-3.52 yuan per meter compared with other sand barrier configurations.It is not recommended to use low height and wide specification mode to fix sand barriers.The optimal configuration is 30 cm height and 1.5m × 1.5m specification,which can save more than 1099.66 yuan per mu compared with other sand fixing configurations.When the protection requirement is higher or the wind speed is higher,the distance between two-way sand barriers at the height of 1.2m can be extended to 10H;in the selection of sand barriers at higher heights.When the cost allows,or use the sand barrier with combination of solid resistance and front resistance and then solid resistance.Selecting the optimal configuration combination.It is suggested that the distance behind the sand barrier in the rear row is 6-8 times the height of the sand barrier.