Keeping commuters on track

Fitch heads the company's rail division and has developed an innovative method of shoring up railway embankments that are spreading under the rails. And the more it rains, the more the soil spreads under the weight of trains and rails. This means that an increasing number of embankments need reconstructing, and Fitch reckons he has the most cost-effective method on the market for doing it.

Costs down 60%
The method, which is one of the most successful Movement for Innovation demonstration projects, has reduced the cost of reconstructing rail embankments from £5000 per metre to under £2000 per metre, claims Fitch. It is difficult to disagree with Fitch's claim, since the method developed for work on London Underground's overground rail is now being exported to the national rail network in the UK and in the Republic of Ireland.

The key to the dramatic efficiency improvement is prefabrication and planning, says Fitch. In the early 1990s, he explains, London Underground's method of tackling embankment slippage was reactive. An emergency call out was made, and local contractors would come at short notice and tackle the embankment reconstruction as best they could, he says.

High call out rates
Tackling embankment reconstruction in this way, explains Fitch, is expensive because emergency call out rates are high. He adds that because the contractors and project teams working on the embankment reconstructions were often different every time, each project team would "reinvent the wheel", with every project adding more cost and offering poor value for money.

Fitch's innovation was to introduce an easily reproducible method – eliminating the reinvention syndrome – and to plan preventative work.

London Underground's problem is that it has 463km of overground rails, many supported by embankments that were constructed over 100 years ago. The method of construction then was simple. Tubs of earth were tipped one on top of another. The clay was not compacted, and the embankments were often finished with a layer of ash. This means that rain and frost are able to loosen the soil easily. So when trains travel over the embankment, soil flows down the side of the embankment from the top corners. This is called a circular failure, says Fitch. The circular failures lead to sleepers settling lower and lower, causing kinks in the rails.

Poor or marginal
When London Underground surveyed its track in 1993, it received a nasty shock, says Fitch. The survey revealed that 438 km of track was in poor or marginal (between poor and OK) condition, with 70 km requiring immediate action. London Underground realised that using traditional call out rates, the remediation of the track be too costly.

Steady workload
London Underground's solution was to create a special earth structures group to find a cheaper way of shoring up the problem embankments. According to Fitch, the group looked to specialist contractors rather than civil engineering generalists and also promised a steady workload for those prepared to keep teams together and work on a standard solution.

Fitch jumped at the chance to become a principal contractor. "Before 1994 we were just another subcontractor. Now London Underground was promising long-term rewards and greater involvement," says Fitch. To help the contractor come up with a solution, London Underground splashed out £300,000 on research from engineer Mott McDonald.

The method Fitch came up with was not rocket science. He analysed the existing method. This involved building an access platform at the side of the track. Then piles were sunk to 8-9m using a small piling rig. The capping was excavated and formwork erected for an insitu capping beam to be constructed in 20m lengths. Fitch discovered that the method was dangerous because the operatives were working on an access platform right next to trains, and that there was a serious bottleneck in casting the capping beam. "It was incredibly difficult to find chippies to do this work," he says.

In one simple move, Fitch has eliminated both the scaffold platform and the bottleneck. By using prefabricated capping beams, he obviated the need for a platform for the chippies to erect their formwork. Now a three-man gang can lay 375m of capping beam a week, compared to 40m a week using the previous method.

Of course, the precast beams cost more to create than insitu beams do, admits Fitch. But, he adds, the costs are more than clawed back because of increase in productivity.

Now Fitch is developing a new, improved method. "By taking out over-engineering in the precast beams, we have been able to make them 70% lighter and 23% cheaper," he claims. "We used to get 13 units on each lorry, now we can get 24 units on," Fitch says proudly. With this increased productivity, Fitch can look to a prosperous future on the railways.