压实风积沙土层盐分迁移规律研究

针对沙漠地区风积沙路基发生盐渍化病害现象,探究压实风积沙土层水、热、盐变化规律。自制下垫面为硫酸钠盐渍土地基的风积沙土柱试验设备,以自然环境条件下6个月(6月—12月)的实时监测数据为基础,分析压实风积沙土层内水、热、盐的时空分布规律与迁移特征。研究结果表明:受外界环境温度影响,压实风积沙土层分影响剧烈区(0～50cm)与薄弱区(50～120cm),随着埋深增加,土柱内部温度变化幅度趋于平缓,各层温度到达峰值具有滞后效应;受含盐下垫面与压实素土风积沙含盐量的浓度梯度作用,压实风积沙土层深部区域被盐分迁入,由无到有。风积沙土层内盐分的存在,为盐分的进一步迁移奠定了物源基础。由外界温度影响,土层浅部受水分赋存形态的变化与蒸发牵引作用,促使水分携带盐分在压实风积沙土层内部逐渐向上发生迁移;盐分在土层整个埋深断面上呈现"高—低—高"的分布特征。受外界环境荷载周而复始作用,压实风积沙土层浅部盐分将渐渐积聚,由少到多,随着时间推移将形成盐渍化病害。

Migration law of salt in compacted aeolian sandy soil

Aiming at the phenomenon of salinization diseases in the aeolian sand subgrade in desert areas, the change laws of water, heat and salt in compacted aeolian sand soils are investigated. The self-made aeolian sand column test device with sodium salinite soil as its foundation is based on the real-time monitoring data from natural environment for 6 months (June to December) to analyze the temporal and spatial distributions and migration characteristics of water, heat and salt in the compacted aeolian sandy soil layers. The result shows that affected by the external environmental temperature, the compacted aeolian sandy soil layers affect the severe (0~50 cm) and weak (50~120 cm) areas. As the depth of burial increases, the internal temperature of the soil column tends to be flat, and the temperature of each layer reaching the peak has a hysteresis effect. Under the effect of the concentration gradient of the salinity content of the salt-containing underlay surface and the compaction aeolian sand deposit, the deep area of the compacted aeolian sand soil layer is moved in by salt, and it is composed of nothing. The accumulation of salt in the aeolian sandy soil layer lays the foundation for the further migration of salt. Affected by the external temperature, the shallow layer of soil is affected by the change of water storage and evaporation, which promotes the gradual migration of water carrying salt in the compacted aeolian sand layer. The salt has a "high-low-high" distribution pattern throughout the depth of the soil. Affected by the external environmental loads, the shallow salt content in the compacted aeolian sandy soil layers will gradually accumulate, and from less to more, it will form salinization diseases over time.