PEOPLE, PROJECTS AND EQUIPMENT Rotterdam Arch “Under” Construction After one of the deepest excavations in the history of the Netherlands, construction of the basement levels has begun for Market Hall Rotterdam. When completed, the structure will be a 12-story-high arch of apartments, shops and restaurants in Rotterdam’s historic Laurens district. Designed by Rotterdam-based architecture firm MVRDV, the 40 m (131 ft) tall and 70 m (230 ft) wide arch will cover a 117 m (384 ft) long, 43 m (141 ft) wide public market. The four basement levels will house a supermarket on the first level and a parking garage on the three lower levels. Describing the location’s geology, Maurice Hermens, consulting structural engineer for Rotterdam-based structural engineering firm DHV, B.V., said the groundwater level starts 2 m (7 ft) below the surface. Yet, the depth of the multi-level basement is 15 m (49 ft). Typical of Dutch terrain, the soil layers have no bedrock to support the heavy structure. The first 20 m (66 ft) consists of peat and clay, then the Pleistocene sand layer to 30 m (98 ft), then the easily compacted clay of the Kedichem Formation to a depth of 40 to 50 m (131 to 164 ft), and then sand again to 70 m (230 ft) deep. With these geological conditions, the Netherlands has used foundation piles for hundreds of years. Indeed, before Market Hall’s excavation began, 2,500 foundation piles were driven into the first sand layer to depths of 27 m (89 ft) for pressure piles, and 29 m (95 ft) for tension piles, Hermens said. Pile driving began in November 2009 and was completed in summer 2010, followed by the excavation, which was completed in fall 2011. Like the above-ground design of the structure, the excavation and foundation of Market Hall are “quite unconventional,” said Hermens. For example, the 90-by-120 m (295-by-394 ft), 15 m (49 ft) deep building pit resembled a large lake during much of the excavation. The pit was flooded on purpose after the first 7 m (23 ft) was excavated, to avoid settling of nearby buildings. The remaining excavation to 15 m (49 ft) was executed under water. Underwater concrete was poured into the flooded building pit continuously for 3 1/2 days (Photo Credit: Provast) Working with Hermens on Market Hall’s design of the excavation, building pit and foundation was Theo de Wit, BBE, geotechnical engineer for Geomet, B.V., a geotechnical engineering firm based in Alphen aan den Rijn, the Netherlands. AUTHOR: Sharon Boranyak Independent Technical Writer Topeka, Kansas DEEP FOUNDATIONS • MAR/APR 2012 • 65
