Excavation of a major basement is underway near of the Swedish city of Gothenburg following installation of hydraulic propping equipment from Groundforce Shorco.
Main contractor Skanska is using the props in a raking configuration to span the 50m by 50m basement on the Valand Quarter 6 project in Kungsbacka.
Conventional bracing was not feasible on this scheme due to cost and time issues, which led Skanska to work with Groundforce in Sweden for the first time. Groundforce specified its 150-tonne capacity MP150 raking props to support the sides of the excavation, with the loads transferred to steel upstand supports driven into the ground.
“None of the props are perpendicular to the waling beam, so corbel connections were needed at the top to connect the props onto the waling beam,” said Groundforce European sales manager Sam Oldroyd.
The location of each upstand, and hence the length of each prop, was determined by the design of the basement and the need to minimise obstructions inside the excavation.
In total, 13 of the MP150 props were installed, eight of them positioned in a fan-shape to support a broad curve that forms one corner of the site.
“We decided to use Groundforce Shorco to reduce the need for welding,” explains Skanska’s project engineer Johanna Fridhagen. “Welding in our projects is very demanding and costly, which means that if we can avoid this to a large extent, the project will benefit economically.”
The only pieces of steelwork ultimately used in the design were the steel beams welded across the three remaining corners of the excavation to act as knee-braces.