Analysis of Settlement Due to Withdrawal of Groundwater Around an Unexcavated Foundation Pit

During the dry excavation of deep foundation pit, groundwater must be pumped within and/or around the pit and the seepage of groundwater forms a groundwater level depression cone around the pit. Drawdown of the groundwater level will cause the increase of effective stress of soft soil. Thus, the soft clay will consolidate and settlement will occur within and/or around the pit. This paper presents a case history on the settlement within and around an unexcavated pit due to groundwater pumping. Before excavation the groundwater was pumped for 260 days and about 0.33 m settlement with in the pit was observed. In order to analyze the variations of groundwater level, seepage in the subsoil, and ground surface settlement, a 3D finite element model, considering groundwater seepage and calculation of ground settlement in one process, was adopted. The analytical result indicates that by using the geotechnical investigated parameters the proposed method can simulate the field measurement value well.