Cutoff Effect on Groundwater Seepage of Underground Structure in Aquifers

摘要

The Quaternary deposit in Shanghai is composed of an alternated multi-aquifer-aquitard system (MAAS) with aquitard over aquifer one another. In the MAAS groundwater system, any drawdown of groundwater head of lower aquifer will cause the consolidation of overburden aquitard. If the underground infrastructure is built in the aquifers, the balanced ground water seepage route will alternate and drawdown will occur in the greater depth of flow, which will cause additional subsidence and unbalancing load on the structures. In order to investigate this impact, a series of numerical analyses are conducted. The analytical results show that the underground structures will cut off the flow of groundwater and change the flow velocity and direction, which will obstruct the replenishment of the groundwater in the urban center. Therefore, even though the total amount of the groundwater pumped does not changed, the groundwater level and the rate of subsidence in the greater depth will decrease. The results of numerical analyses indicate that the extent of impact depends on the depth and width of the underground structures installed in the MAAS layers.