填海造陆区盐分运移过程室内模拟与分析

Laboratory simulation and analysis on the salt migration process of coastal reclaimed land

在半湿润气候环境下,围填海区的表层土壤正面临着复杂的盐渍化问题。以压实填土为研究对象,通过土槽模型再现了潜水蒸发与侧向壤中流共同作用下的盐分运移过程,以探明围填海区的盐渍土形成机制。结果表明,在蒸发作用驱使下盐分向上补给,表层土壤的初始积盐类型为CaSO_4,海水对填土层的盐分补充导致积盐类型转变为CaCl_2和NaCl。在陆相渗流作用下,填土中将形成相对稳定的渗流状态。自由水面线以上为积盐状态,盐分类型以CaCl_2和MgSO_4为主;自由水面线以下为脱盐状态,盐分类型以CaCl_2和NaCl为主。土壤水盐的运移将改变酸碱度环境,pH值将随着含盐量的增加先下降后上升。在陆相地下水的补给下,填海造陆区的盐渍化防治工作应当重点关注地下存在挡水层或建筑物基础密集的地区。

In the semi-humid climate,the surface soil of coastal reclaimed land is faced with a complicated salinization problem.To investigate the formation mechanism of saline soil in coastal reclaimed land,we studied the salt migration process under the joint action of phreatic evaporation and lateral interflow.The results showed that the initial salt type in the surface soil is CaSO4,and it gradually transitions to CaCl2 and NaCl in the salt accumulation process.Under the action of terrestrial seepage,a stable wetting front moves to the coast while the water table rises.The area above the free water surface is in a salt accumulation state,with CaCl2 and MgSO4 as primary salt types.The area below the free water surface is in a state of desalination,with CaCl2 and NaCl as primary salt types.Water and salt movement will change the pH value of the soil environment.The pH value will first increase and then decline as the salt content increases.Under the condition of terrestrial groundwater recharge,the salinization prevention and control work in coastal reclaimed land should focus on areas with underground water barriers or densely distributed building foundations.