As part of London Underground’s long-term maintenance and upgrade programme, extensive structural investigations were undertaken across covered ways and tunnels along the network. Although many of these assets, some over 150 years old, remained structurally sound, assessments identified a long-term risk of fatigue failure within cast iron beams providing primary support.
In July 2010, CRL was awarded the contract to strengthen the cast iron beams supporting Covered Ways 17 and 20 on the District line near Embankment station. Installed between 1864 and 1870, these historic beams support the Victoria Embankment Gardens and form a critical element of London’s subterranean infrastructure.
Services undertaken
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Structural strengthening of cast iron beams
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Installation of UHM CFRP plates
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Abrasive blasting and surface preparation
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Priming of cast iron beams
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Bonding of CFRP plates to structural elements
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Application of protective paint system
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Works undertaken during engineering hours
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Delivery within restricted access environments
The strengthening works focused on mitigating long-term fatigue risk while preserving the integrity of historic assets within a constrained underground environment. CRL was appointed to install Ultra High Modulus Carbon Fibre Reinforced Polymer plates to 91 cast iron beams across Covered Ways 17 and 20. In total, 182 CFRP plates, each measuring 7.5 metres in length, were installed, with 76 beams strengthened in Covered Way 20 and a further 15 in Covered Way 17. This solution provided a highly effective means of increasing load capacity without altering the original structural form or imposing additional dead load.
Prior to strengthening, each beam was thoroughly prepared through abrasive blasting to achieve a suitable surface for bonding. Following preparation, the beams were primed to protect the substrate and ensure optimal adhesion. During subsequent shifts, the beam surfaces were re-cleaned before the CFRP plates were carefully bonded into position. This staged approach ensured consistent quality control despite the restrictive working environment and limited access. Once installed, all plate edges were cleaned and detailed before the application of a protective paint system, COPON Hycote EA9 WB, providing additional durability and long-term protection.
All works were undertaken under significant operational constraints. Access to the site was restricted via a vent shaft located within Victoria Embankment Gardens, and activities were limited to engineering hours between 01:00 and 05:00. Actual working time was often reduced to approximately three hours per shift due to London Underground safety procedures for isolating and reinstating traction current. Despite these challenges, CRL delivered the programme efficiently through meticulous planning, disciplined execution and experienced supervision, ensuring that strengthening works were completed safely, accurately and in full compliance with underground operational requirements.
"Strengthening the old cast iron beams required a bespoke solution with each of the carbon fibre plates being made to measure. CRL has a lot of experience in using the system and the work has been progressing well.”
LUL Spokesperson
The strengthening of the Embankment line covered ways delivered long-term resilience to vital underground infrastructure while preserving historically significant structures. By adopting UHM CFRP technology, CRL provided an efficient solution that mitigated fatigue risk, enhanced structural performance and avoided intrusive interventions.
The application of protective coatings further improved durability, reducing future maintenance demands and supporting London Underground’s wider asset management strategy. Careful planning around restricted access and engineering hours ensured operational continuity and passenger safety throughout.
The success of this project reinforced CRL’s reputation for delivering complex structural repairs UK, leading directly to further similar contracts across the London Underground network.
