The Design and Construction of a Fast Track 16 Hectare, 18 m Deep Basement in Soft Clay in Singapore

Singapore’s newest integrated resort, Marina Bay Sands, was completed in record time and has garnered numerous engineering awards. The development sits on recent sand reclamation, which in turn rests on deep soft marine clay deposits. With an average excavation depth of around 18 meters, the 16 hectare (39 acre) waterfront development involved some of the largest marine clay excavation in Singapore. About 2.8 million cubic meters of fill and marine clay were excavated from the site equating to about 800 trucks a day for two years. To overcome the challenges of the bulk excavation and minimize shoring in difficult soil environments, innovative excavation solutions were developed to enable an accelerated construction timetable for this project involving densely packed site works with complex staging and interface issues. These included the use of unsupported circular excavations up to 130 meters in diameter and continuously reinforced 1.5 meter thick diaphragm walls acting in shear. To add to the challenge, a 35 meter deep ‘cut and cover’ tunnel next to the Singapore’s longest bridge, the Benjamin Sheares Bridge, was required. To enable the bridge to tolerate the inevitable imposed lateral displacements of an abutment, the structural system of the existing bridge was modified to allow it to safely articulate in plan.