Groundwater Control In Design And Construction Of Deep Basement Excavation In Singapore

In a highly built-up city like Singapore, newer developments revolve around constructing deep underground basements due to its limited land space. This constraint constantly challenges engineering methodologies especially in groundwater control and in the design and construction of deep basement excavation works. Most excavations below the natural ground water table will inevitably induce pore pressure reduction and drawdown in groundwater table. Some of the key factors that affect the change in water table are type of geologies, excavation support system and the excavation depth. Control of groundwater during deep excavation can also be attributed to reducing horizontal stress behind the retaining wall leading to pore pressure control, high permeability soil constituents underneath the toe of the wall and leakage through the gaps or openings. In this paper, three case studies are featured where 18m to 25m deep excavations were carried out for underground basement construction in the heart of Singapore City. How the control of groundwater was considered in design and implemented in construction methodologies of deep basement excavations is presented and groundwater behavior observed during the course of excavation in different soil conditions are presented coupled with the field monitoring results.