Written by J. Murphy & Sons Limited
Innovative construction techniques used by J. Murphy & Sons Limited on a tunnel brickwork repair project for Network Rail, not only overcame local difficulty and produced time and cost savings, but are now set to improve production rates at other sites, as Paul Mohan from the project team, outlines.
Across its miles of rail track and infrastructure, Network Rail has the ongoing challenge of a continued programme of tunnel repair and refurbishment. Usually the working environment is difficult, with tunnels being dirty, damp and difficult to access. The work is carried out at night in short possession times meaning that set up and running costs are high.
J. Murphy & Sons Limited (Murphy) has undertaken these repair works for many years with varying degrees of success. The works on site require operatives working at height using access platforms and scaffold. Skilled tradesmen bricklayers place the grout by hand, which is very often a back breaking task. Consequently production rates, which are the key to success, vary with the conditions.
While carrying out pointing to brickwork during tunnel repairs at Totley Tunnel we experienced a recurring problem in completing the work in wet areas of the tunnel. The tunnel is located on the former Midlands Railway Manchester-Sheffield line on the outskirts of Sheffield and Grindleford in Derbyshire. This resulted in repeatedly being unable to fully complete the remitted work.
A new approach
The Murphy team recognised there was scope for intelligent approaches to solving the problem faced. It was considered that if a mechanised system could be found to inject the grout; it would then be possible to increase the production rates with the potentials for the work to be less onerous.
The team, comprising contracts managers, foreman, site managers, mechanics and fitters, began brainstorming ideas. The leading objective became a mechanised system for injecting the grout. The team wanted to identify how the problems of water dripping, sometimes flowing through the cracks, could be overcome.
Other questions raised were; how would the Murphy team transport the mechanised system to the work site, set up and achieve any worthwhile production rates in such short possession?
One member of the team recollected a nozzle system several years ago that looked good but never quite worked because the nozzles kept blocking. The idea had a massive effect on the project. However there were technical issues to overcome to resolve the ability of team to operate in an isolated harsh working environment.
Firstly; grout supply companies were contacted to investigate the viability of using quick drying grout and a partner company was found. The next stage was the kit; difficulties existed in locating this but further research by the Murphy team found the person who had designed the original equipment and was able to train our operatives once the team had modified the equipment and made it more operationally reliable.
The innovative system is based on injecting pozzament to a nozzle from a pressure pot which then mixes with the sodium silicate from a second pot as it is injected into the joint, coined the Aerocem system.
The Aerocem system
There were similar systems on the market but none that utilised the sodium silicate. The addition of the sodium silicate causes the mortar to flash set; this then enables the pointing to be carried out in wet conditions.
The method of working is evidently better as it produced the positive knock on benefit in that railway operations are less susceptible to closures of railway lines due to possessions.
Network Rail appreciated the noticeable difference made as for them it enabled them to deliver an improved service to the end user/customer as less disruption and line closures were required.
The Aerocem system was underway and subsequently introduced at Totley to repair the tunnel brickwork. There were some teething problems all of which were overcome, and production rates were increased by 50 per cent. The client was pleased with the time and cost saving but ultimately appreciative of the resulting train service operation improvements that would ensue.
Innovation was achieved by enabling the team to work without undue restriction which encouraged them to think outside of conventional working methods. In addition to this the team worked together solving each problem as it arose.
At times; particularly when the grout consistency caused blockages; solutions seemed difficult to overcome. However, Murphy’s ethos of a ‘can do’ approach to construction meant that at every juncture the team worked through the problems without considering or fearing failure. The team settled upon the attitude that any failure was part of the learning process.
From this construction innovation in using an Aerocem system for grouting tunnel brickwork; a further eight operatives have been trained and we now have three Aerocem gangs available for further projects of this nature.
Murphy has developed an innovation that delivers improved service to the customer; Network Rail.
The use of new techniques has enabled Murphy to complete numerous remits which were previously too wet to point using conventional methods, the largest being 1000m2 in Totley tunnel.
Client satisfaction has increased as Murphy can now virtually guarantee the completion of the remitted items. A remit for Disley tunnel identified that 60 per cent of the pointing work required would not have been achievable due to the conditions without the Aerocem equipment.
Of Murphy’s innovation, Pete Shrader, Network Rail, Site Manager stated:
“The Aerocem works were applied to a high standard with 7bar pressure used. I witnessed the pozzament being applied and was happy that the joints in the brickworks were being filled to a high standard.”
Typical output by a four man Aerocem team can achieve up to 100m2 of repair work in a shift, in any conditions, compared with 30-40m2 using conventional methods in reasonably dry areas only.
Murphy is now applying the innovation at other sites as part of its Minor Works Framework for Network Rail.