滨海地区咸淡水界面上含水介质水敏感性的实验

WATER SENSITIVITY OF POROUS MEDIA AT SEAWATER-FRESHWATER INTERFACE

根据野外水文地质调查和研制的实验装置,在大沽河下游采集砂土样品,采用有机玻璃土柱进行咸水和淡水驱替试验,并通过盐浓度的突变和渐变来研究咸水-淡水界面的水敏感性。研究结果表明,当淡水驱替咸水时,含水介质的渗透性降低64%;但是,随着含盐量逐渐降低,渗透性降低缓慢,其降低幅度为50%;盐度降低越快,其渗透性降低的的速率越大。此外,观测到渗透性随着时间明显降低,而且这种降低是不可逆的。由于流入液含盐量的迅速降低,从含水介质释放的黏土颗粒(伊利石、高岭土和绿泥石)产生运移和截获,最后导致渗透性的变化。

According to hydrogeologic investigation in the fields and a developed experimental setup, seawater and freshwater were made to flow through a plexiglass column filled with samples from the downstream of the Dagu River. Water sensitivity at saline water-freshwater interface was studied by changing salinity sharply and gradually. The results showed that the permeability of porous media decreased by 64 when seawater was flushed by freshwater. However, the decrease of permeability was comparatively slow and the permeability decreased by 50% in the case of gradual salinity decrease. The faster the rate of salinity decreased, the larger the reduction degree of the permeability was. A significant decrease of hydraulic conductivity was observed with time and the decrease was irreversible. Due to rapid salinity reduction of the influent, the migration and interception of the released clay particles such as illite, kaolinite and chlorite resulted in the permeability change.