We cracked it! Anchoring underground structures
Urban Life 23 June 2016 Abhijeet Kulkarni
Creating structures below ground and under high water pressure is challenging. And when even anchors cannot withstand the forces of the ocean, you need to get creative.
Curved between the base and tip, a new supertall residential tower on the edge of the Dubai Marina seafront most of all resembles a glass and steel banana.
The arcing structure of DAMAC Heights is 335 metres high, so it might come as a surprise that one of the toughest construction issues lay beneath the ground. Here, a two-sided water pressure from the Persian Gulf on one side and the Dubai Marina on the other posed a major challenge for the construction of a five-storey underground car park.
With 20-metre deep excavation, it was difficult to minimise the water ingress and provide safe working conditions.
Water ingress can usually be stopped by anchoring the shoring walls. But in this case, the proximity of the marina lake and the immense water pressure behind the walls made anchoring below the marina too difficult. Keeping the site dry required innovative thinking:
We used a two-stage construction approach: First, we installed anchored diaphragm walls on three sides of the plot. Then, on the challenging marina side, we created an unanchored diaphragm wall in combination with secant walls that allowed us to excavate before stabilising the wall.
We had to install the first secant wall 20 metres inside the plot along the marina side, where the earth was strong enough to hold the anchors in place and thereby allow excavation for the first phase. We then used the first-phase constructions to support the struts in the second phase by propping the marina-side diaphragm wall to take the earth and water pressure.
Once completed, the 85-storey building will be the United Arab Emirate’s seventh tallest residential tower and among the world’s top 20.