The Greater Cairo Metro is the first underground in Africa and the Arab World, it is considered among the most technologically advanced mass transit system in the world . It is the best economical system for an efficient reduction of the road traffic.
It forms the backbone of the Metro network in Cairo as it passes through the most important residential and business districts of the city. The line was formed by connecting the existing railway line from Helwan in the South to the existing railway line to El Marg in the North East by means of a new underground line beneath the central business district of Cairo. The Total length of the line is 44 Km including 34 stations. The length of the underground section is 4.5 Km including 5 underground stations. The Project commenced in 1982 and ended completely in 1989.
Line 1 was designed to carry 60,000 passengers per hour in each direction, in electrically powered trains comprising 9 cars each, with a headway of 2.5 minutes and a maximum speed of 100 Km/hr and a track gauge of 1.435 m.
Diaphragm Walls were used to support the sides of the excavation during the phases of construction and became part of the structure by being joined to the raft and roof , thus forming the cross-section of the tunnel and stations. Precast walls were usually used in the tunnel section and cast in-situ walls were used in the stations. Trenching for the walls was done using cement/bentonite slurry for the precast walls and bentonite slurry for the cast in-situ walls.
A grouted plug was used between the diaphragm walls at their toes. The grout consists of cement/bentonite followed by soft silica gel. The function of the plug was to reduce the permeability of the soil to permit dewatering of the excavation with limited discharge and without affecting the level of the groundwater outside the walls to ensure the stability of the adjacent buildings. The precast panels in the tunnel sections were 0.45 x 2.5 m with 12 m length. The cast in-situ walls thickness varies between 0.6 to 1.0 m depending on depth.
It was executed by a joint venture of 7 French companies and the arab Contractors headed by Interinfera company and below are a list of works constructed by the Arab Contractors:
- The civil work for a main tunnel of 681 meters long in the sector between El Sayeda Zeinab and Saad Zaghloul stations a part of the tunnel, 295 meters long is a U shape open cut with a width rangeing from 12, to 21.25meters the walls were either cast in site or diaphragm.
- The remaining part of the tunnel is of a box shape with a width ranging from 8.86 meters to 12 meters, its walls are precast.
- Rerouting all services ducts such as potable water and sewerage networks, electric cables, telephone line and gas pipes which encountered the Metro path.
- Removing all structures and buildings which obstructed the tunnel path from Ramses station to the new El Sayeda Zeinab station.
- Construction of a high pressure station and testing transformers building in Tora.
- Construction of washing station equipped with the necessary sets to wash the movable units at Helwan.
- Construction of 4 electric powers stations distributed equally along the tunnel to provide the electrical power necessary for operation.
- Construction of 3 cooling stations to adapt the temperature inside the tunnel.
Value: L.E. 14,176,431
Unlike Line 1, Line 2 is a wholly new line. The Line extends from Shubra-El-Kheima station to Om-Elmasreen Station with a total length of 19 kms and 18 stations. The Line is currently extended to Monib Station. Line 2 provides interchanges with Line 1 at Mubarak and Sadat stations. It also provides interchanges with the Egyptian Railways at Shubra-El-Kheima, Mubarak and Giza Stations. The Line includes 6 Km of at-grade and viaduct section with 6 at-grade stations, cut and cover tunnels of length 1.8 Km, bored tunnel of length 9.5 Km and 10 new underground stations besides the development of the two interchanging stations at Mubarak and Sadat Stations. Line 2 was completely finished on October 2000. On 2005 an extension of has occured in Line 2 , 2.60 km to the south. This included the construction of two new at-grade stations, Sakiat-Mekky and El-Monib stations.
For the bored tunnel section, a single tunnel 8.35 m in internal diameter was constructed using two Herenknecht bentonite slurry shield TBMs, each 9.43 m in diameter. The tunnel has a bolted precast concrete segmental lining, each 1.5 m wide and 0.40 m thick. It should be noted that it was the first time that the River Nile was crosses by a bored tunnel underneath the bed of its two branches.
The underground stations are typically 150 m long, 21 m wide and 23 m depth, each having three levels. They have been built using top bottom construction between diaphragm walls 1.2 m thick and extending down to 55 m below ground level. The water table was about 2 m below the ground level. Soil injection was used to form a low permeability plug, 7 m in thickness, at the base of the walls.
The trains have a design maximum speed of 80 Km/hr with a minimum headway of 105 seconds, transporting about 1.2 million passengers per day.
Line 3 will extend from the north west of Greater Cairo at Imbaba to the north east at Heliopolis serving also the Cairo International Airport. The Line shall cross under the two branches of the River Nile. The total length of the Line is approximately 30 km most of which is bored tunnel. The stations will be constructed by the cut and cover method. The basic design is currently in progress.