Lifting/Moving of Structures - Jacked Sliding
Because of severe damage to the concrete from alkali-silica reactions, the entire structure had to be replaced. The new structure, a 410 m long, nine span and 5,500 t heavy dual carriageway road deck, was jacked sideways 12.2 m into position using Ø36 mm DYWIDAG Bars (THREADBAR®).
Sliding was chosen as it minimized traffic disruption and was significantly cheaper than traditional methods. The new deck initially carried traffic while resting on temporary supports.
After demolition of the old viaduct, eight new concrete piers and two abutments were built to support the new deck. Road closure was limited to a weekend - eight hours for the slide, 24 hours to allow bearing grout to set and the remainder for asphalting and traffic re-routing. The merge slide was downhill on a 2.85 % slope. Balance between pushing and pulling forces gave a controlled pulling force of up to 5,700 kN. Pulling was incremental, governed by the jack stroke of 600 mm, enabling a rate of travel of up to 1.8 m an hour.