Soil improvement works for an offshore land reclamation

The Changi East reclamation project was carried out in five phases along the foreshore of the east coast of Singapore. The water depths in the reclaimed area ranged from 5 to 15 m. The project involved hydraulic placement of 272 million m³ of sand onto soft seabed marine clay up to 50 m thick. A linear total of 170,000 km of prefabricated vertical drains (PVDs) were installed for accelerating the consolidation process of the underlying soft marine clay. The soil improvement works covered a total area of approximately 1200 ha. In this paper, the site conditions and the soil improvement works adopted are described. Pilot tests with full-scale field instrumentations as well as laboratory and in situ tests were carried out to verify the design, check the effectiveness of the soil improvement works using PVDs, and establish the most suitable drain spacing. Field monitoring data obtained from both the pilot tests and the reclamation works are presented and interpreted. Degree of consolidation was calculated based on both settlement and pore pressure data.