Abstract:

The features of concave surfaces,the effect of erosion and deposition,grain size parameters of sediment (including average particle size,standard deviation,skewness,and kurtosis) were analyzed separately in three polylactic acid(PLA) sand barriers with different specifications,1 m × 1 m,1.5 m × 1.5 m,and 2 m × 2 m,which were laid on the flat sand in Ulan Buh Desert,Inner Mongolia,China.The concave surfaces and sediment grain size characteristics of the surface layer (0-3 cm) were measured using graduated sticks and laser diffraction methods after the wind season.The results showed the three kinds of PLA sand barriers could form stable concave surfaces.Along with the growth of sand barrier specification,the depth of surfaces increased while the erosiondeposition coefficient decreased in the range of 1/12-1/10.The profiles in different directions basically fitted the quadratic curve;nevertheless,the intensities of erosion-deposition varied widely.The 1 m × 1 m and 1.5 m × 1.5 m sand barriers stayed in the deposition,of which deposition intensities were respectively 50.08,5.6 times the erosion intensities.The deposition intensities were 1.1 times the erosion intensities and the erosiondeposition volume per unit was 0.02 g·cm^-3 in the 2 m × 2 m sand barriers.In terms of particle size and composition,we found that the sediment was mainly composed of very fine sand,and with the exception of the 1 m × 1 m specification,the retardation effect of PLA sand barriers resulted in a rapid decrease in the content of very fine sand.The height of the PLA sand barriers was 6-8 cm.The 1 m × 1 m and 1.5 m × 1.5 m sand barriers with large deposition intensities were prone to sand burial and required additional labor costs for re-laying.The 2 m × 2 m sand barriers,blocked to erosion and deposition balance,were beneficial to perform the long-term protective effect of sand barriers.Considering the cost and protection effect of sand barriers,it was concluded that the 2 m × 2 m PLA sand barriers were suitable for flat sand or weak wind condition,and provided a scientific reference for reasonable application in sediment control engineering.

Key words: polylactic acid(PLA), different norms, concave surface, grainsize characteristics, Ulan Buh Desert