Abstract:

In order to accurately predict the dynamic characters of groundwater seepage field and land subsidence caused by dewatering of deep foundation pit in loose sediments, a ground settlement coupling model was established in this study. In this coupling model, three dimensional variable-parametric non-steady seepage of precipitation of deep foundation pit and one-dimensional consolidation theory based on Terzaghi were used. The porosity, permeability coefficient and water storage dynamic changes with the decline of groundwater level were also considered. And a three dimensional fem numerical method was applied to solve the model. The dewatering of the deep foundation pit in Puzhu Rd station, metro line 3, in Nanjing was taken as a case study. The results showed that an optimal project was obtained by adopting 15 dewatering wells for the pit, locating the filters of the pumping wells at depth of 22.0-37.0 m and defining a pit’s diaphragm wall at a depth of 41.5 m. By using this project, groundwater level could meet the excavation requirements and surface settlement outside the pit could also be within the controlled limits. The coupling model proposed was proven reasonable and reliable. And it has more credibility to use the theories in the article to simulate and predict the groundwater flow in deep foundation pit dewatering in similar areas.

Key words: loose sediment, deep foundation pit dewatering, three dimensional seepage, variable-parametric, numerical simulation