塔里木盆地南缘风沙土盐结皮形成机理以及抗风蚀性能研究

Salt crusts are thin cementation layers of soluble salts on the surface soils in arid and semi-arid regions of the world. Salt crusts on soil surfaces are strength; it can reduce particle entrainment by wind. However, the resistance to wind erosion of salt crusts has not captured people's attention. Salt crust is not fund in the technologies of controlling wind and sand. With the perspective of using salt crusts to control wind and sand, this study chooses the salt crusts as research objects on the southern margin of Tarim Basin. Particle sizes and salt ions of salt crusts soil will be tested in laboratory, it is expected to find the distribution laws of particle size and salt ions of salt crusts soil. Basing on the laws of particle size and salt ions of salt crusts soil, the artificial composition test of salt crusts will be done in field and laboratory, it try to find the thresholds of the particle size composition, the thresholds of salt ion composition,the content of salt ion, the rate of moisture evaporation, the intensity of rainfall that influence salt crusts composition, and real the formation mechanism of salt crusts. Using the wind tunnel testing the salt crust resistance to wind erosion, it want to find the salt crust type and thickness that can be used to resist natural sand erosion, and provides a basic theory for the using soil salt crust controlling wind and sand.

盐结皮是地表形成的一层易溶性盐薄胶结层，具有一定的强度，可以抵抗地表风蚀，并广泛分布于干旱与半干旱地区。然而，盐结皮的抗风蚀性一直未引起人们重视，在风沙治理中一直未见其踪影。本项目从利用土壤盐结皮治理流动风沙土的角度出发，选择塔里木盆地南缘风沙土盐结皮为研究对象，测试风沙土盐结皮的土壤颗粒粒径和盐离子组合，揭示风沙土盐结皮的土壤颗粒粒径特征和盐离子特征。在揭示盐结皮物质组成特征的基础上，进行野外和室内盐结皮人工形成试验，试图找到形成风沙土盐结皮的颗粒粒径组成、盐离子组成、盐离子含量、水分蒸发速度、降水强度等因素的阀值范围，揭示盐结皮形成机理。运用风洞测试盐结皮的抗风蚀性能，寻找可用于抵抗自然风沙流侵蚀的盐结皮种类和厚度，为运用土壤盐结皮治理风沙流动提供理论基础。

盐结皮是干旱、半干旱地区地表形成的一层易溶性盐胶结层，具有一定的强度和抗风蚀性。然而，盐结皮一直未被人们重视，其形成机理尚未明确。本项目从利用盐结皮治理流动风沙土的角度出发，研究自然盐结皮的土壤颗粒粒径和盐离子特征，进行盐结皮形成试验以揭示盐结皮形成机理。在塔里木盆地南缘对风沙土盐结皮进行调查采样，测试盐结皮表层土壤颗粒粒径和盐离子含量，结果显示：自然盐结皮表层（0-15cm）的盐分主要是NaCl（石盐），GaSO4盐含量最高出现在表层盐结皮下部；表层结皮主要是NaCl胶结土壤颗粒，下部结皮则主要是GaSO4盐胶结土壤颗粒；盐结皮的土壤颗粒径粒径变化差异较大，土壤颗粒粒径对结皮影响较小。用回弹仪和硬度计对自然盐结皮层的抗压强度进行测试，结果显示：自然盐结皮的抗压强度差异十分大，最大的抗压强度超过了200kg/cm2，最低的不足2kg/cm2；表层结皮抗压强度与结皮厚度、表层土壤含盐量以及抗风蚀性能呈正相关关系。在风沙土上进行盐结皮形成试验，试验结果显示：风沙土表层均可以形成盐结皮，盐结皮表层亮度随着盐含量提高逐步由灰色变为白色，随着盐含量的增加表面粗糙度、盐结皮强度和结皮厚度逐步增加。地下水埋深对自然盐结皮影响较大，超过2m将难以形成地表盐结皮。该研究初步揭示了盐结皮机理，将有助于人们进一步了解盐结皮，并利用盐结皮特性治理流动风沙地。