Costing around £15 billion, the new underground rail line across London is the largest civil engineering project currently in Europe and presents huge engineering and construction challenges. Employing about 7,000 people on 40 worksites throughout London and the South East, the project involves constructing 42km of new rail tunnels under the City linking existing Network Rail services from Maidenhead and Heathrow in the west and Shenfield and Abbey Wood in the east. New underground stations at Paddington, Bond Street, Tottenham Court Road, Liverpool Street, Whitechapel and Farringdon are also being constructed.
Sitting right at the heart of the London network, Farringdon Station between Charterhouse Square and Smithfield Market is fundamental to the project. When complete, more than 140 trains per hour will flow through the Farringdon interchange and because it is the only station from which passengers can access all three networks - Thameslink, Crossrail and London Underground services - it is set to become one of Britain's busiest train stations.
The station is split into two worksites - the Eastern Ticket Hall (ETH) and the Western Ticket Hall (WTH) - both surrounded by residential and commercial properties and typically congested London streets. Earthmovers visited the Eastern Ticket Hall which has the long-reach JCB JS220 at the heart of its current spoil away activities.
Groundworks have already been completed by Laing O'Rourke/STRABAG joint venture and construction work is now being carried out by GFK – a joint venture between BAM Nuttall, Ferrovial Agroman and Kier Construction. The Group is involved in three Crossrail contracts valued at more than £700 million including two 6.2km tunnel drives between Royal Oak and Farringdon, a contract to construct early access shafts and sprayed concrete lining works for Bond Street and Tottenham Court Road station tunnels and the contract for the main construction works at Farringdon Station.
Excavation in the City of London brings its own particular 'problems'. At Farringdon digging down to 35 metres for the new ETH will be needed to complete the station construction. Initial excavations have revealed skeletons of 13 adults under Charterhouse Square which archaeologists believe are victims of the Black Death which struck London around 1350. There may be as many as 50,000 plague victims in the area as Farringdon is a known burial ground for plague victims.
The East Ticket Hall site is also adjacent to Smithfield Market the largest and oldest wholesale meat market in the UK dating back almost one thousand years. The site was the home of jousts and tournaments in the 12th century and then an execution place for criminals including Wat Tyler and William Wallace. The foundations of the current Grade II building – built in 1868 – are very close to a new escalator barrel which goes down to the new platforms and therefore requires extensive underpinning and jacking to ensure there is no movement or settlement of the structure. Compensation grouting – a technique which precisely injects cement grout via small-diameter underground pipes which radiate from a central 'grout shaft' into the ground to fill an area where settlement is expected - will also be used to minimise settlement.
Large items of construction equipment are usually moved to and from sites in Central London at around 3 to 4am however with the adjacent Smithfield busy from 1am to 6am Sunday to Thursday it means plant movements have to be organised Friday and Saturday evenings.
On three edges of the site are old low-weight bearing rail arches (from a previous underground station at Smithfield Market and the original Barbican station) making it even more difficult to position heavy equipment such as a large mobile crane. This restricts the size of equipment (20 tonnes maximum) that can be lifted in and out of the lower work levels which is currently about nine metres below street level. This meant that the excavator chosen to install and remove the large earth ramp constructed to allow the large piling rigs to access the lower level had to be as small and light enough to access the site and work from the upper road level yet have a dig depth of at least nine metres and very good reach.
Because of the noise restrictions an unusual silent, vibration-less sheet piling pressing system technique rig was used. Using four powerful hydraulic clamps which hold of the tops of the interlocked steel sheet piles, the rig applies about 200 tonnes of downward pressure pushing on all piles until the rig reaches its safe load limit. Maintaining this initial pre-load the hydraulic cylinders then apply a vertical force to a single sheet pile whilst reacting on the rest of the pile group – sort of a push-pull technique. Once all piles in the group are advanced by the hydraulic clamps full stroke of all hydraulic cylinders, the entire pressing device retracts and repeats the cycle along the whole run of sheet piles.
JCB long reach
After consultation with Lynch Plant Hire – one of the main equipment rental companies working with the major contractors and equipment supplier for the Farringdon Station site – it was decided to use a JCB JS220 long reach excavator which when fitted with an 8.7 metre boom and 6.4 metre dipper has a maximum dig depth of 11,990mm and a maximum reach of 15,600mm. The better the reach the more ramp material can be removed reducing the work of a smaller excavator operating at the lower level.
While long reach excavators are generally designed for waterways maintenance applications and fitted with ditching or weed mowing attachments, it is an effective muck-shifter when fitted with a general purpose 0.5 cu m bucket and seen on many applications such as ports, sand pits and city centres requiring the long reach capability. Weighing 23.7 tonnes, the very stable JS220 is one of the mid-range excavators in JCB's long reach line-up which extends from the 13 metre reach JS 145 to the 21.1 metre reach JS 360 LC.
Operating the machine is Lynch operative Bash Kim. The Albanian-born driver has been operating machines for about nine years the last six with Lynch mainly wheeled and tracked excavators up to 45 tonnes.
"Because of the depth of the spoil below the level of the tracks the JS 220 long reach was the obvious choice," said Kim. "The machine is powerful and quick which makes it ideal for loading trucks. Currently we are doing about 30-35 loads a day which is disposed of in Dartford. The excavator could easily cope with almost double that but traffic and the number of available wagons reduces this number."
"The machine was used to build an earth ramp to allow the large piling rigs to track down to the lower level. It also worked at the lower level clearing around the old tunnels, building a work platform for the piling rigs and clearing up when finished," he said. "Now this has been completed it was tracked back up to street level and is now working at removing the ramp. Because of the length of the ramp and the fact that the JCB can only work from one position at the top of the ramp, a smaller 13.5 tonne zero tail-swing excavator is helping push the spoil closer so that I can reach it and load the trucks. When completed the smaller excavator - which is light enough – will be lifted from the lower level by a crane."
Engine emissions and DPF
Power for the JS 220 is supplied by an Isuzu 4HK1X Tier 3 emissions compliant engine producing 128kW (172hp) at 2000rpm which has 25 percent more power, 27 percent more torque and better fuel consumption than previous engines.
JCB has, however just launched a brand new JS220 model at Bauma 2013, which is the first JCB excavator above 20 tonnes operating weight to adopt the company's highly-efficient Ecomax diesel engine. It will result in Tier 4i compliance, a 10 percent cut in fuel consumption and improved engine responsiveness without the need for any exhaust gas after treatment.
All equipment on the Crossrail contract has to comply with strict engine emissions noise regulations and dust pollution. On the JS 220 that means a diesel particulate filter (DPF) has to be fitted. This was added at the JCB factory and has been neatly installed within the unmodified engine canopy. The machine is also is fitted with a simple red/green light cab mounted emissions monitor which alerts the driver should emissions be too high – perhaps when the engine temperature changes. However temperature control on the JS 220 is helped by a bank of radiators mounted side by side. One is for the engine coolant, while a separate section is for the engine's intercooler. A third section is designed for keeping the hydraulic oil cool. Keeping the engine at the optimum temperature helps maintain performance and helps reduce engine emissions."
All Lynch Plant equipment – excavators, telescopic handlers, trucks and trailers - have been modified to comply with the various Crossrail requirements for emissions, noise and road user safety particularly for cyclists.
The latest JCB JS excavators – the 11 to 15 tonne JS 115, JS 130 and JS 145 – all feature Stage IIIB/Tier 4 Interim Ecomax engines and claim to be the only crawler excavators in this weight category that meet the current emission standards without the need for a DPF or an exhaust after treatment additive. The latest engines also give an additional 10 percent fuel savings and are slightly quieter.
The JCB Ecomax engine achieves this through innovative, patent pending combustion technology which uses 2,000 bar common rail injection pressures, variable geometry turbocharging for rapid low rpm response and cooled exhaust gas recirculation (EGR). This means that no costly DPF or after-treatment additives such as AdBlue is needed saving customers money and allowing designers to create a more compact engine compartment.
"The JS 220 is an easy machine to operate with great all-round visibility, even to the rear because of its low engine cover," said Kim. "It has an auto mode for optimum performance as well as an Advanced Management System which also has four selectable work modes – auto, economy, precision and lifting – which get the best out of the machine whether economy or maximum power."
"Everyone on site is very pleased to see the distinctive yellow of a JCB excavator arrive on site," said Rob Lynch director of Lynch Plant Hire. "JCB has a very good image and the performance and reliability is excellent. This JS 220 has an aftermarket fitted DPF and monitor however the latest excavators with the new Ecomax engines would be able to operate on site without any costly emissions controls. The current engine is very fuel efficient and this makes a huge difference in the fuel costs of the machine for the client."
"From a maintenance point of view the service access is excellent with most items being able to be carried out at ground level which not only reduces downtime but is much safer for fitters working on site," said Lynch. "A hinged belly plate makes getting to the engine sump very simple and there is a quick-fit drain pipe for use on engine-oil and fuel-tank drain plugs. All the steps and top covers are fitted with non-slip, heavy-duty panels. The in-cab digital display which is part of the AMS checks for engine oil and fuel filters. Overall the JCB JS 220 is the perfect machine for the job."