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Contractors working on Norway’s most ambitious building project – the Fjord City redevelopment – have successfully completed a large and complex basement with help from modular hydraulic supports and real-time load monitoring supplied by Groundforce.


The project, which is probably better known by its nickname, the “Barcode”, comprises a series of high-rise buildings on former dock and industrial land in central Oslo. The huge common basement, up to three levels deep and covering 35,000 sq m beneath 15 units, is in soft Oslo clay and made-up ground. It therefore needed strong and rigid support.


A vital requirement was that nearby structures – including a major road bridge which passes just 7m from the excavation – had to be protected from damage caused by ground movement. This was especially challenging as the site was already affected by ongoing natural settlement calculated at around 30mm per year.


“Once we had decided on a modular system for the propping, it was natural for us to work with Groundforce” says project engineer Vidar Flatekval of Kynningsrud Foundations “We had already worked successfully with Groundforce on a project in Tronheim also in Norway.”


Groundforce supplied 22 of its MP250 props, its biggest standard hydraulic struts, each with a nominal capacity of 250 tonnes. These were installed in three levels to support the sheet-piled retaining walls while specialist contractor Kynningsrud excavated to full depth.


The excavation was completed in sections with the support system dismantled for re-use and “leap-frogged” into position as each new section commenced.


This required the development of a precise sequence of removal and repositioning. “Groundforce faced a logistical challenge to ensure we remained on programme” says Arne Tveit Eigeland of consulting engineers, Multiconsult. “We could have done the propping with traditional steel work but this entails a lot of work and doesn’t lend itself to re-use” he adds.


Kynningsrud quickly mastered the re-installation sequence and, despite the fact that the largest props were 28m long and weighed more than 18 tonnes each, was soon relocating each one in less than two hours.


Continuous real-time load monitoring was a fundamental requirement of this operation. “We needed a system of integral load monitoring to measure real-time loads and monitor load changes due to excavation” says Arne.


On this contract, which began during July 2013, temperature fluctuations created huge increases in loadings (from 260 tonnes to 340 tonnes) as the props expanded during the day.


Kynningsrud installed water sprinklers to regulate prop temperatures and thus managed to achieve a constant load of 270 tonnes. “There’s no way we could have responded to the increase without using real-time load monitoring” says Vidar Flatekval.


Sam Oldroyd, European Sales Manager for Groundforce said “There have been some substantial developments in the product range over the past few years and the Barcode project was a perfect application for our systems.  It demonstrates our ability to supply projects of all sizes across Europe.


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