NaCl含量对风沙土盐结皮特性及其抗风蚀性能的影响

Effects of NaCl Content on Salt Crust Properties and Wind-erosion Resistance of Aeolian Sand Soil

土壤盐结皮能够抑制水分蒸发,减少地表粉尘释放,在干旱区生态环境中具有十分重要的作用。为了获得干旱或半干旱区风沙土盐结皮的合理盐溶度,选取新疆塔克拉玛干沙漠东部风沙土为试验土壤,分别加入0.1%、0.2%、0.5%、1.0%、2.0%、3.0%、4.0%、5.0%、6.0%和7.0%(盐占混合物的百分比)的NaCl进行盐结皮试验,测试盐结皮的强度和韧性。利用电镜观察盐结皮微观结构,分析NaCl盐溶度对结皮抗压强度以及其抗风蚀性能的影响。试验结果表明:NaCl含量对风沙土结皮抗压强度和韧性有较大影响,随着NaCl含量的增加盐结皮的强度和韧性均呈先增加后降低的特殊现象;但盐结皮的抗压强度峰值和韧性峰值不同步,NaCl含量3.0%时,盐结皮韧性达到峰值;NaCl含量4.0%时,盐结皮的抗压强度才达到峰值。盐结皮表观和微观结构显示,盐含量大于4.0%后结皮盐晶体出现盐斑聚集,这种盐晶体聚集导致盐结皮不均匀,进而导致盐结皮抗压强度复杂变化。

Soil salt crust can inhibit water evaporation and reduce dust release on the ground,it plays a very important role in the ecological environment of arid regions.In order to obtain the reasonable salinity for salt crust of aeolian sandy soil in arid or semi-arid areas,0.1%,0.2%,0.5%,1.0%,2.0%,3.0%,4.0%,5.0%,6.0% and 7.0% NaCl were added to aeolian sandy soil collected from east Taklamakan Desert in Xinjiang,the strength and toughness of salt crusts were tested by piezometer,the microstructures of salt crusts were observed by electron microscopy,and then the effects of NaCl content on the compress strength and wind erosion resistance of salt crust were analyzed.The results showed that NaCl content had great impact on the compress strength and toughness of salt crust,with the increase of NaCl content,the strength and toughness of salt crust increased first and then decreased.However,the peaks of compress strength and toughness of salt crust were not synchronized,which appeared at 3.0% and 4.0% of NaCl content,respectively.Spotted aggregation of salt crystal appeared on soil surface after NaCl content>4.0%,which led to unevenness and complicated changes in compress strength of salt crust.