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Sun February 28 2021

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Ground stabilisation saves material at Tilbury2

31 Jan 20 The O’Keefe Group has used cement stabilisation techniques to prepare the site of a decommissioned power station for its redevelopment as a container storage facility for the Port of Tilbury.

O'Keefe preprared the ground for container storage
O'Keefe preprared the ground for container storage

The £200m Tilbury2 port terminal, which is next to the existing 930-acre site in Thurrock, is set to become the UK's largest unaccompanied freight ferry port and the country's biggest construction processing hub.

O’Keefe is nearing completion of groundworks on the part of the site on the north bank of the River Thames at Tilbury that was previously part of a coal-fired power station, demolished in 2017. O’Keefe started work on the site in April 2019 and hands it over to Graham in February.

Principal contractor Graham is transforming this part of the development into a storage facility for containers at the Tilbury2’s roll-on/roll-off container terminal.

The 250,000m2 brownfield site has been levelled and compacted to a 30% CBR (California bearing ratio) value before a layer of quarried type-1 aggregate can be laid as a base for the final reinforced concrete paving slab.

The task has been made complicated by the presence of numerous underground structures, namely concrete foundations that supported the now-demolished buildings.

O’Keefe had to excavate all the obstructions and crush them down for re-use as aggregate to back-fill drainage and service trenches.

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The main technique employed was cement stabilisation, mixing cement powder with the soil in-situ. Once incorporated and evenly mixed into the soil, the cement cures, effectively stiffening the soil and increasing its bearing strength.

O’Keefe used a pair of Wirtgen soil stabilisers to mill the soil while mixing the cement into it, followed by a Cat D6 dozer to level and compact the ground.

A fleet of 30-tonne tracked excavators, fitted with breakers and pulverisers dug out and broke up the buried concrete; a Pegson crusher processed it into re-usable aggregate.

“The main advantage of soil stabilisation on this project is that it has allowed Graham to use site-won material and import less aggregate,” said O’Keefe’s contracts manager Brian Doogue.

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