Abstract: This paper presents a case history of three-dimensional groundwater seepage simulation by commercial software Visual MODFLOW for the Lvshuiwan Station of No. 11 Line in Nanjing. The numerical groundwater seepage model of the diaphragm wall supported deep excavation considered the type of deep excavation, geological and hydrological conditions at the project site. The influence of various embedment depths of diaphragm wall into the bedrock on the groundwater seepage field inside and outside of the excavation as well as the deformation induced by the watering operation was investigated. The results indicate: The argillaceous silty sandstone bedrock embedment has an obvious groundwater retardation effect. With the increase of embedment depth, the groundwater table outside the excavated area decreases, but the height of water table decrease is relatively small. It is not cost effective of minimizing the groundwater reducing by only increase the bedrock embedment depth of the diaphragm wall. However, adequate bedrock embedment can effectively increase the time of groundwater water drop as the result of dewatering inside the excavated area, so that the ground subsidence induced by the rapid groundwater drop can be positively delayed. The required bedrock embedment depth can be determined by considering the adjacent environment, stability of the deep excavation, construction cost and other constructability.

Key words: diaphragm wall, deep excavation of subway station, deformation of supporting structures, groundwater seepage field