Study On The Effect Of Geometric Shape On Wind Protection And Sand Fixation Effects Of Two Kinds Of Sand Barriers

This experimental research area is located on the edge of the Jilantai Salt Lake.The study focused on different shape biodegradable poly lactic acid(PLA)sands barrier units and different shape straw barrier units which of shapes were triangle,round and square,respectively and which of size were 0.25m2(size A),1m2(size B),2.25m2(size C)and 4m2(size D).We measured wind speed,sand-transporting quantity,surface sediment grain-size characteristics and deposition and erosion characteristics in the different shape sand barrier units,and compared the bare sand which was the same feature.By comprehensive analysis of the wind protection and sand fixation effects of the sand barrier units,we got the following conclusions:(1)The roughness of the surface was increased,the surface wind speed was reduced and the sand-transporting quantity of the surface was reduced after laying the sand barrier units.When the wind speed was 6m/s,the effects of wind protection for the PLA barrier units were between 0.55%and 7.52%higher than in the straw barrier units.When the wind speed was 8m/s,there was a big difference in effect of wind protection between the three shapes of sand barrier units.The effects of wind protection for the triangle sand barrier units were between 3.97%and 9.36%and 4.46%and 11.89%higher than in the round and square sand barrier units,respectively.The roughness of the triangular barrier units was 1.12?1.27 times and 1.14?1.57 times of the circular and square barriers,respectively.With the increase in height,the sand-transporting of the surface in the sand barrier units increases first and then decreases.The average grain-size of sand transported in the barrier were smaller than the average grain-size of bare sand,and fine sand,medium sand and very fine sand were the main fractions of sand transporting particles.(2)In the three shape barrier units,the surface soil particle content of fine sand,medium sand and very fine sand accounted for 35.60%Y58.00%,23.20%?47.00%and 6.00%?18.00%,respectively.Compared with surface soil particles of bare sand,the particle sorting into the sand barrier units was worse than that in the bare sand.The content of fine sand in the sand barrier units was 1.2%-13.2%higher than in the bare sand,and the content of fine sand was 1.2%?23.6%higher than in the bare sand.The fine sand,medium sand and very fine sand in the sand barrier units were sensitive to the change of flow field,and were the main fractions that causes the change of sediment particle size.(3)The coefficient of deposition and erosion was between 1/33.3 and 1/14.3 in the sand barrier units.the results of erosion and deposition was mainly deposition in all sand barrier units.The height of deposition and erosion in the size 0.5m2 sand barrier units were between 9cm and 15cm,and the other three was mainly between 3cm and 15cm.The deposition strength was between 7.90g/cm2 and 12.78g/cm2.The deposition strength of the PLA barrier units was 1.05 times that of the straw barrier units,and the deposition strength of the triangular barrier units were 1.01 times and 1.04 times that of the round and the square,respectively.