Parts of an EPB tunnel machine will be arriving at Marseilles docks on the French Mediterranean coast in July for loading and transport to Egypt. From there they will be moved to the capital Cairo and assembled in September for the second phase works on the city’s third metro line.

The 9.4m outside diameter machine, from TBM maker NFM in France, will join a brand new Herrenknecht bentonite slurry TBM from Germany, arriving shortly before. The new Herrenknecht machine will be used to complete the first phase of the project, taking over from an existing 9.4m diameter Herrenknecht slurry machine, which is currently stuck in a section of now frozen ground, following a hole-through incident late last year.

This first Herrenknecht machine, christened Cleopatra, had already driven just under 4km on phase one of the new line when the suspected misplacing of two segments in the lining allowed an inflow of the water laden gravels and sands the TBM was passing through. With some 20m head of water this was a process that did not stop until the void had unravelled all the way to surface.

“Fortunately, no one was injured either at the surface or inside the tunnel itself,” says project manager Jean-Pierre Dauban, for French contractor Vinci Construction Grand Projets. Vinci is lead contractor in a consortium building the tunnels for both the initial 5km plus phase one and a second stage that extends the work another 5km eastwards. Phase two overlaps phase one and was begun last year.

The alignment for the new tunnel is mostly along the centre of Cairo’s relatively wide roads, and the hole-through during phase one happened under El Geish Avenue here—so there was no collapse or undermining of structures. Some damage to nearby buildings was sustained but otherwise the incident has caused problems primarily for the contract team, flooding the last section of the existing tunnel and drowning the machine itself.

“The situation on the surface has been rapidly controlled and came back to normal within a few days for the people living around, with the exception of the traffic on the avenue which was stopped to repair the sinkhole,” says Dauban.

“But to overcome the problem we were obliged to flood the tunnel with water including the TBM machine after having built a wall some hundred meters behind the back up. This was necessary to stabilise the water pressure in the ground and avoid further collapses,” he explains.

Since the cut-off wall was created, the area around the machine has been made watertight with a ground freezing operation, he says, carried out by subcontractor Bauer. The freeze, along the machine and 25m of tunnel beyond, allows the construction of a shaft in front of the cutterhead from which it will be possible to access the machine and dismantle it to take it away for repair.

He hopes this can be achieved by the end of this year. The shaft is already complete and clean-up and repair of the tunnel itself is underway.

Despite the incident and the complex ongoing rescue operation, which has cost the project some 11 months on its already tight schedule, Dauban is still optimistic that the first section can be completed on time. The new machine should be able to start a drive from the far end in August completing the outstanding 1,200m by the year’s end, with E&M and signalling to follow in short order. “We have adopted some acceleration measures for those,” he says.

Meeting demand
Opening of the line is on a very tight schedule, due in October next year, which is politically an important moment in the country when the president, Hosni Mubarak, finishes a term in office. Completion will have an immediate impact on the city. Line 3 is much needed as a complement to the existing two lines built in the last two decades, both by Vinci or rather its predecessor companies.

The two original lines run north-south, more or less along the Nile riverside, and the system is already counted as the 15th busiest in the world, with more than 700 million passenger rides annually. But even that makes little impact on the traffic that jams the streets; anyone who has visited the city in the past few years will know that even simply crossing the road is a hairraising business of threading through a never-ending stream of cars.

It can only get worse. Cairo is one of the fastest growing cities in the world, a megametropolis with a population of 6.8 million in the city proper and another 10 million in suburban areas and possibly already much more than that, as a constant inflow from the countryside expands it. Cairo’s population is also one of densest in the world.

Line 3 will cut across the city, east to west, eventually making a connection as far out as the city’s airport on one side. On the other side it will join up important suburbs in a Y-shaped route with branches heading north and south at that end.

The two current phases under construction will be the busiest sections, serving the centre parts of the city. Phase one runs from Attaba near the Nile where the line will connect to the existing Line 2 in a deep, multilevel station, and heads east for 5km towards the airport. It includes five stations. Phase two takes this onwards another 6.5km with another four stations.

Phase three will extend the Attaba end across underneath the Nile river and is itself split into three sections, a 5km long stem of the “Y” and the two branches of 6km and 7km, the main one heading down close to Giza. Design for these sections is underway but tunnelling is not due to start until 2011.

A final phase four will finish the connection towards the airport with another 11km of tunnel and seven stations.

The latter two phases are not yet let, though Vinci is hopeful of getting them, not least because there is a significant tranche of French foreign aid money involved in each of the project stages. A negotiated agreement was made at the time of the first award that it should get the second stage as long as the cost arrangements did not increase over the first phase.

Cutting Line 3
Vinci is lead contractor with 28.5 per cent of the project in a full consortium with three other partners; Arab Contractors, Bouyges, and Orascom. Initial design of the route is by French transport specialist Systra, producing a part detailed design with full engineering design by the contractor group itself. The group was also well placed to win the initial EUR 226M (USD 283M) contract after making significant experiences in Cairo on the first two metro lines. The TBM Vinci had been using on the first phase until the hole-through was one of the original two machines used on those lines.

“The machine had been in France where it was reconditioned,” says Dauban “and then brought back.”

Work on the project was let by client the National Authority for Tunnels, part of the Ministry of Transport, in April 2007 to start in July with tunnelling beginning the next year. A three-month train test period was to be part of the 48-month schedule.

Despite the problem at El Geish, the tunnelling is relatively straightforward says Dauban. The machine drive began from an entry shaft just beyond the fifth Abbasia station at the airport end of the section heading back and made good progress, averaging some 12m a day but with peaks of 20m plus achieved.

It goes entirely through Nile river bed deposits, with a high water table creating a head of pressure between 20-30m, conditions most appropriate for a slurry machine. Spoil is recovered from the used slurry at a single separation plant about halfway along the route.

The difficulties of working in Cairo emerge at this point, because the spoil must be stored during the day for removal only at night when the traffic levels drop to some extent. Subcontracts with local companies see to the removal and disposal of spoil, the later of which is not a great problem once you are 40km from the city in the surrounding desert.

Permanent support
A standard segment pattern is used for the tunnel, with seven main segments and a key. Each is 1.5m long, 200mm thick and weighs 5.7t, and the ring is grouted from the tail of the machine with a conventional cement grout, producing an 8.4m internal diameter tunnel.

The total 22,400 segments are made at a precast plant in the suburbs by a subcontractor, Bona Pipes, which is one of Cairo’s biggest concrete pipe manufacturers. The company also did the segments on the Line 2 project.

“We supplied the moulds, and other equipment and they poured the concrete,” says Baudan. “We were able to re-use four mould sets from the previous project though there is also one new one, and we have added another two for the second phase work.”

Again, delivery to site has to be at night. Permitting for street possessions and deliveries has also been a significant part of the work on the stations says Dauban.

These have been made using full possessions of the streets, rather than in the logistically more complex half side occupations, but that has meant complicated traffic diversions and arrangement have been needed.

The stations are 150m long boxes, mostly with two levels inside for concourse and platforms, and in most cases about 30m deep.

“The last station at Attaba is deeper, about 50m, and has five levels,” he says. “This is the interchange with Line 2.”

Stations are built beginning with diaphragm walls to about 40m depth. Specialist Bauer as done most of these using hydrofraise type machines though for the deeper walls at Attaba, which go all the way down to underlying clay layers for watertightness, the consortium used Intrafor/Bachey because it was the only one with machines available for reaching up to 100m depth, as required.

One the walls are in place, a base seal is created by grouting and then top down construction has been used. The intermediate floor slabs, made on the way down, provide structural support for the next section. Concrete arrives from one of three batching plants set up to ensure the deliveries never have to travel more than 1.5km. Arascom, Egypt’s main cement supplier and now part of Lafarge, operates the plants.

“The lowest slab in the stations is not made until the TBM passes, however,” says Dauban, “and so we have to use steel tubular strutting at the bottom.” The TBM reaches each station after excavation and is pushed by hydraulic rams across the intervening space on rails.

Steel bell
To get the TBM into the station space Vinci has devised an intriguing steel bell system.

“Normally you would have to grout a watertight block in the ground outside the diaphragm wall to avoid leakage problems at the boundary,” Dauban explains.

Instead, a special bell shaped steel casing is set up, attached to the diaphragm wall on the inside. It has a double layered skin with a bentonite fill inside to provide a flexible seal (see Figures 1 and 2).

Inside this the TBM begins its forward progress, assembling and grouting its segment rings as it passes through the 1.2m thick concrete wall, so that a tunnel junction is formed “automatically.” The wall has no special “eye,” just the normal concrete, Dauban explains.

“We used the ‘cloche’ first for an exit of the machine but now are also using it for entry into the box as well,” he says. “It is less costly than a full grouting of the ground.”

Until the TBM hole-through, progress on this machine was good. Dauban is hopeful that it will go well with the new Herrenknecht machine, which is to the same specification as the older one,”but with modern technology.”

Later phases
Meanwhile attention is turned also to the second phase works, which were let last year. An initial drive of nearly 2km for this will be made using the new Herrenknecht that will have to be brought from the first phase tunnel once it has completed. But further eastwards the geology changes as the river deposits give way to the river valley base rock and the desert beyond, a mixture of mudstones and sandstones.

To make this drive the consortium will use the EPB from NFM, which is just finishing its test trials at NFM’s works in France. “The rock is not too hard,” says Dauban.

Mucking out will use a rail mounted system with two separate trains made of seven mucking cars each, which can be moved in parallel inside the tunnel and inside the TBM back-up.

The phase four section of the route, which should begin in 2012, would also run through this kind of rock.


Cairo’s metro system is the 15th businest in the world, but the streets are still jammed A standard segment pattern has been used for the tunnel The tunnel lining stops at Abbasia Station and the TBM is winched through Figures 1 Figures 2 – A bell-shaped, steel casing has a doublelayered skin with a bentonite fill that provides a flexible seal