Hanger Lane Underpass Detached Parapets

The Hanger Lane Underpass in North West London is part of London’s North Circular Road. This vital part of the road infrastructure required specialist structural repairs because the parapets, which have very large copings, were becoming detached. Transport for London contracted AWT to install remedial fixings and stabilise the underpass.

case study 56e19ecd3de943.09306548 1 - Hanger Lane Underpass Detached Parapets

The Structural Issues

Action Wall Ties’ expertise was sought to undertake the securing of large concrete copings to the Hanger Lane underpass retaining walls. The specification, provided by Transport for London, was to introduce a pattern of large stainless steel fixings to be drilled down into the concrete of the wall.

This presented a series of obstacles to overcome. Firstly, to enable the proposed drilling we had to initially design equipment and methods to enable the efficient drilling for the pattern of fixings. Secondly, we had to be self-sufficient for the delivery of water and electricity supply to the working place on truck mounted working platforms, together with all that is involved in working on the closure of a major road at night.

case 52 a - Hanger Lane Underpass Detached Parapets

The Structural Repair Solution

To enable the efficient drilling Action Wall Ties designed and manufactured four working saddles that clamped over the head of the wall, each supporting two diamond core drilling rigs set at the correct spacings with connections for water, electricity and lighting.

case 52 b - Hanger Lane Underpass Detached Parapets

case 52 b 1 - Hanger Lane Underpass Detached Parapets

To provide water to the diamond drills we mounted a large water tank and pumps with a diesel generator supplying power into a large Sprinter van, together with other mobile generators which provided the services required for the proposed works.

case 52 c - Hanger Lane Underpass Detached Parapets


With the access platforms in place the AWT designed manufactured drilling saddles were lifted and clamped into place and connected to the services (as listed above). Adopting wet diamond drilling techniques a pattern of 20mm holes 400mm deep were drilled. Each saddle was set in place to drill two holes simultaneously, and a second set by sliding the rig forward before resetting the saddle, deploying four maned drilling saddles to meet with the program.

case 52 d - Hanger Lane Underpass Detached Parapets

case 52 d 1 - Hanger Lane Underpass Detached Parapets

The pre-drilled holes were cleaned before we resin bonded 16mm stainless steel grip bars, and made good the disturbed areas with coloured concrete repair mortar.

AWT can provide cost effective structural repairs for a wide range of structural faults including large infrastructure projects. We operate not only in London but across the whole of the South East of England. We have experience working on the road and rail network including work for Transport for London, many London borough councils and public sector organisations across the South East.

Action Wall Ties (AWT) are specialist structural repair contractors for large and small projects. Please get in touch to discuss your requirements. Contact us on 01227 721 255, or email us.

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