The deformation of aquitard is the main contribution to land subsidence in the North China Plain, and the water released from aquitard compaction may be a large portion of the exploited groundwater. In this study, the consolidation test was employed to understand the mechanics on the drainage and deformation of aquitard. The results suggested the strain of aquitard mainly resulted from the difference of hydraulic head between aquifers. And it was decreased with depth of aquitard at the same hydrodynamic pressure. In contrast with the interbed within aquifers, the aquitard was deformable when it was compressed. The weakly bound water was significantly released when the void ratio was about 0.44–0.45, and the EC of water released from the aquitard was decreased with the compacting process. The data from the consolidation test suggested that the pumping of groundwater from aquifer III might be less contribution to the land subsidence with respect to other aquifers in the future.
Through collecting groundwater samples from the coastal region of Tangshan, China, the hydrochemical processes that affect the chemical composition of groundwater and the quality of resources were analyzed. Chemical constituents, factor analysis, and a graphic method were employed in this research. The results show that human activities obviously affect fresh groundwater. The deep groundwater distributed in the southern part of the region is severely affected by salinization, and the shallow groundwater in the north is also beginning to show the same deterioration. The chemical concentrations of the deep groundwater depend largely upon the water-rock interaction, the mixing of saline water and the ion exchange processes. With the exception of sample C-33, all the groundwater samples in the study area are suitable for drinking. Tests show that roughly half of the deep groundwater samples have at least one water quality index indicating that it is chemically doubtful or unsuitable for irrigation. Therefore, it is concluded that deep groundwater is becoming an unacceptable resource to irrigate areas located near the coastline because the groundwater quality in the study area is exhibiting signs of degradation. This study＇s findings contribute to a better understanding of groundwater resources in order to support regional management and protection.
