Parliament Square gets upgrade

Custom-designed centrifugal cast GRP pipes have been used to reline a 250m section of damaged brick sewer which runs from Parliament Square in Central London to the Victoria Embankment, alongside the River Thames.

The 2100 dia pipeline, was manufactured and supplied by the UK’s Johnston Pipes, and consisted of 34mm thick pipes split into six segments to allow them to be passed through a narrow access shaft. Patented longitudinal ‘H’ section strips then joined the segments to allow the contractor to reform a circle in the existing sewer.

Once the pipes were secure, the annulus between the liner and old brickwork was filled with grout.

Johnston Pipes’ business development director, David Smoker said, ‘Durability was a key requirement in the choice of pipeline material used for this project. The contractors needed a liner which was able to withstand the imposed load of traffic in the area.’

Flexibility was another key point in Johnston’s favour as GRP pipe is manufactured in sections which makes it easy to assemble underground.

The company’s GRP pipe has also been used to answer a vertical challenge on a major sewer relief tunnel project on the river Orwell in the east of England for Anglian Water.

Lightweight pipes, capable of withstanding the aggressive nature of sewage, were used by Contractor AMEC Tunnelling to line five vertical drop shafts of up to 48m deep which connect the existing sewer network to the relief tunnel. The pipes were moved from horizontal to vertical in segments using purpose-built lifting and support clamps.

Specially designed trestles were also used at both sides of the vertical shaft entry to support base, intermediate and upper pipes throughout the lifting and placing operation.

To secure and joint the pipes, mechanical harness rings were used as they were lowered down the shaft. Harness ring tie rods were positioned and torqued to make the joint.

The joining sequence was repeated adding 6m lengths of pipe until the shaft bottom was reached.

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