Egypt’s biggest TBM, the 9.3m diameter Herrenknecht EPB, called Nefertiti, successfully broke through on the first of two drives for a new road tunnel in mid-September. The 1.6km long, two-lane tunnel passes about 25m under the Islamic El Azhar district, with its narrow streets and ancient mosques.
A JV of France’s Campenon Bernard and Egyptian contractor Arab Contractors has won the design+construct work for the new underpass taking traffic from the central Opera Square to the famous ‘City of the Dead’ Moslem cemetery on the edge of town.
The project, which began in August 1998, will create two parallel tunnels 10m apart and 2.6km long, with approximately 400m of cut+cover constructed at either portal. The drive just completed is the central TBM section of the first tunnel and is lined with precast concrete segments. The TBM is being dismantled and the cutting head has already been lifted out of the reception shaft. It is on its way to the 100 x 30m launch shaft for the 1.8km second drive.
The machine was used on the recently completed second metro line, another Campenon job.Project manager Pierre Giraud hopes that it will see work on a third line as well.
Cut+cover sections, launch and recovery shafts, and three other ventilation shafts have been constructed using 1m thick diaphragm walls. These have been built by subcontractor Bachy Soletanche up to 35m deep into the generally firm sands and gravels underlying 10m of general fill.
Excavation of the almost complete southern tunnel has gone extremely well under the 200 year old buildings, with differential settlement claimed to be no more than 2-3mm.
