Regional line of the Cairo metro

Regional Line of the Cairo Metro M o h a m e d El Hosseiny Abdel Salam

Abstract---Completion of the first phase of the Cairo metro's regional line in 1987 was a milestonefor Cairo, which was the first city in Africa and the Middle East to adopt this modern means of transport. The regional metro line serves the Greater Cairo population of 10 million. The line includes 33 stations, five of which are underground stations in the central business district, and transports 400,000 passengers per day. The author discusses the project in terms of the site geology of central Cairo, the design concept for the metro, the method of executing the excavation, the interior design of the stations, and the electrical~mechanical works.

he city of Greater. Cairo, situated on the east and west banks of the River Nile, has had a growing demand for public transport. With a total population greater than 10 million, Cairo has one of densest concentrations of people in the world. Like other large cities, Cairo cannot hope to solve its transport problems without constructing a metro system on the major routes, where it is obvious that other means of transport fail to satisfy requirements. A transportation and traffic study for the Greater Cairo area was carried out in the early 1970s by the Egyptian Ministry of Transport through a joint venture of French/Egyptian consultants. The study proposed, among other things, a metro network comprising three lines (see Fig. 1): Line R - R m A regional line with a 2.90-m gauge, realized by the underground junction of Helwan railway line south of the city of Cairo with the El Marg railway line on the northeast, for a total length of 42.5 km. Line U 1 - U I m A first urban line, 13 .5 km long with a 2.60-m gauge, between Giza, southwest of the city, and Shoubra E1 Kheima on the north. Line U 2 - U 2 ~ A second urban line, 10 km long with a 2.60-m gauge, between Embaba, west of the city, and Darrasa, east of the city.

T

Present address: Mohamed El Hosseiny Abdel Salam, Chairman, National Authority for Tunnels, 56 El Ryad Street, EIMohandissen, Cairo, Egypt. This article is reprinted wlth permission from the proceedings of the ISF International Congress, 13-15June, 1988. Tunnelling and Underground Printed in Great Britain.

R~sum6---L'ach~vement en 1987 de la premiere pha~e de la ligne de M~tro r(gional marque un (tape importante pour la viUe du Caire qui est la premise cit~ en Afrique et au Moyen Orient ~ se doter de ce moyen de transport moderne. La ligne r~gionale de n~tro dessert les 10 millions d'habitants du Grand Caire. La ligne comprend 33 stations dont 5 souterraines dans le centre des affaires de la cite et transporte environ 400 000 voyageurs par jour. L'auteur aborde le projet du point de vue de la g~ologie du centre du Caire, de la conception du M~tro, de la m~thode d'ex~cution, du parti architectural de ramknagement des stations et des Equipements Electrom~caniques.

First priority was given to the regional line because it constitutes the backbone of the great population center and runs through the most important residential and business districts of the city. The regional line includes 33 stations, five of which are underground stations in the city center (Central Business District). It is designed to carry 60,000 passengers per hour in each direction in electric trains composed of nine cars each, having a headway of 2.5 minutes and a maximum speed of 100 km/hr. The execution of this line was divided into two phases. Phase One, completed in September 1987, involved a 28-km section running from Helwan to Mobarak station in Ramses Square. A 4.5-km underground section on this line included five underground stations, two of which are two-level interchange stations to serve both the regional line and the future urban line. This phase also included the annexed struct u r e s - 3 refrigeration plants, 23 ventilation stations, 4 air-extraction stations, 14 rectifier stations to supply 1500 volts D.C., a 20-kv distribution network, a high-voltage electrical supply main transformer station fed at 66 kv, 1 washing machine for rolling stock, and 2 pumping stations for drainage. Phase Two included the electrification of the existing line from Ramses Square to El Marg, modernization of some stations, and construction of three stations and renovation of the tracks. This phase was completed in spring 1989. The route of the underground section of the regional line passes through intensely congested areas, very close to buildings and public structures. However, the planners made maximum use

Space Technology, Vol. 4, No. 3, pp. 279-283, 1989

0886-7798/8953.00 + 0.00 ~) 1989 Pergamon Press plc

of existing streets and publicly owned ground and open space to minimize the need for demolitions, underpinning and land appropriation. Site Geology of Central Cairo The central part of Cairo was built in the Nile valley on several hundred meters of recent alluvial and diluvial deposits, which are underlain by the upper Eocene limestone marine formations. It is postulated that the Nile River developed its course through this area after the downfaulting of a huge limestone block extending between the Mokattam cliff and the Pyramid plateau. The Nile River has significantly changed its course through the Cairo area. The river's meanderings through-

\X._.~B~,\~/.~-,E,

"~XX

ELMARG R

s.ou.. EL "~"~'. t U,

uz~ ,,t

~.*J

CAR I O0.,¢gs?.

OrVfR

•.

~( '

~

,,

RELG O ZZN FNAL HELWAN

Figure 1. General layout of the metro lines for the Cairo metro project.

279

out ancient times have been the major source of soil deposited in the area. The regional metro line runs through areas previously occupied by lakes and the course of the river. As a result of important fluctuations in the Nile, combined with the shifting o f the water course, the sand deposits in this area alternate in an intricate manner with layers or pockets of silt or clay. In addition, some of the abandoned branch channels and lakes were filled in manually, mainly during the nineteenth century. Hence, a surficial layer of heterogeneous mixture o f silt, clay, sand, bricks, pottery, and blocks of limestone is commonly encountered at these locations. The main features of the soil (see Fig. 2) are surface layers of fill with a thickness varying from 3.0 m to 8.0 m. Under these layers are clay silt and silty clay layers with pockets of very fine sand, underlain by a deep-seated medium to fine sand. Lenses of silt and clay are occasionally found in the sandy layer, which frequently grades to silty sand. The water level is 1.5 to 3.0 m below ground level. Since the construction of the High Dam, the fluctuation o f the water level has been limited to -+ 0.5 m throughout the year. T h e sulphate content in the ground water is generally high.

Design Concept for the Regional Metro Line Owing to the geological and hydrological properties of the soil, as well as the proximity of the u n d e r g r o u n d line to existing buildings, and in order to keep the cost as low as practicable, the cut-and-cover method was adopted for the tunnel and the stations. T h e longitudinal section was established nearest to the g r o u n d level in order to limit earthworks under the water table. T h e diaphragm walls used to support the sides of excavation during the phases o f construction became part of the structure by being joined to the roof and the raft forming the crosssection of the tunnel and the stations. Sulphate-resisting cement was used, with 400 kg/m s of concrete, to resist the aggressive action of the groundwater. T h e diaphragm walls were either precast units or cast in-situ, depending on the thickness and depth required by the design. The technique of grouting the soil between and u n d e r the side walls was adopted. T h e grouting injection was carried out in two phases--first, by cement bentonite; and second, by soft silica gel, in order to form a plug between the side diaphragm walls. T h e level of the plug was estimated to provide the required stability to the bottom o f the excavation during the earthworks. The function o f the plug was to allow dewatering o f the excavation with limited discharge and

280

ii GROUND SUR~CE

(O}

-r t.rl bJ Q

i

i

i

Figure 2. Configuration and soil profile at tunnel section.

without affecting the water level outside the walls o f the tunnel, to ensure the safety o f the adjacent buildings.

Method of Execution (Fig. 3) T h e works began by identifying the existing public utilities and diverting these utilities either permanently or temporarily. T h e trenching for the walls was carried out between guide walls and u n d e r cement/bentonite slurry for prefabricated walls, usually in the tunnel; or under bentonite for cast-insitu diaphragm walls, usually in the stations. When the trenching reached the designed level, the prefabricated units were placed or the concreting under bentonite was cast, forming the two side walls of the section. The prefabricated unit was 0.45 × 2.50 x 12.00 m, while the thickness of the cast-in-situ diaphragm walls varied from 0.6 to 1.0 m. The u n d e r g r o u n d line was divided into sections by lateral cut-off made of cement/bentonite slurry. The cut-offs were slurry walls dividing the tunnel length into small sections. T h e upper parts o f these cut-offs were removed during the excavation. Thus, each zone for grouting was limited by the two side walls of the tunnel and the two cut-offs. T h e injection tubes were drilled between the side walls and the cut-offs, and cement/bentonite was injected at the designed level of the plug, followed

TUNNELLINGAND UNDERGROUNDSPACETECHNOLOGY

by the injection of the soft silica gel to form the plug (the permeability o f which was checked by a pumping test). The excavation was performed either in the open air or under the roof slab, depending on the authorization period for each job site. Either the roof slab was cast between the walls, followed by reinstatement o f the site, and excavation under the slab was performed with one-level strutting of the walls, after which the raft was cast; or the excavation was performed in the open air with two-level strutting, and the raft was cast before the slab. With the casting of the roof slab and the raft, the section was complete. T h e internal dimensions of the section were 6 . 0 m x 8 . 8 m for the tunnel, 6 . 0 m x 18.80 m for the regional station, and 5.3 m × 14.70 m for the urban station. Watertightness was ensured by a waterproofing layer on the slab and under the raft, and by water-stops placed between prefabricated units and the slurry lining on the walls. Main quantities for the works are shown in Table 1. During the progress of the works, many difficult conditions were encountered that required the utmost care and skill. For example, the columns of the flyover of Ramses square had to be underpinned until their loads were transferred from their piling foundation to their new support on the roof slab of Mobarak station. This

Volume 4, Number 3, 1989

ent levels and intervals. The identity of each station is associated with the color of its logo. The stations are named in honor of famous Egyptian leaders. The portrait of the leader for which the station is named is placed on the end wall of each ticket hall.

Figure 5. Mobarak station is characterized by the Islamic sole of design. Table 1. Main quantities [or the work on the Cairo metro, regional line. Items of Work Diversion of Public Utilities

Total Quantities 65000 m

Civil Works Injection works boring injection materials Moulded Walls Concrete Reinforcements Excavation

814000 m 156000 m3

388000 m 3 47000 tons

1,000,000 m3

Cooling Pipes

9850 m

Insulation

10500 m2

Cables

110000 m

High Voltage 66 kv cables

24000 m

20 kv Cables Helwan - El Sayeda Zeinab El Sayeda Zeinab - Mubarak Cables trough

800000 m 200000 m

42500 m

High Voltage Station Low Voltage Cables 20 kv Cables

Volume 4, Number 3, 1989

Financing

5600 u n i t s

Ventilation

42000 m 7000 m

Electrical/Mechanical W o r k s The power supply comes from 66-kv national network through two different sources and four lines, to which the main high-voltage station is connected. Major transformers in this station feed the metro network through 20-kv lines running along the metro line. The alternative current (AC) is modified to direct current (DC) through the rectifier station to produce the 1500 V that feeds the catenary. The transformers in the light power station provide 380-V current for lighting and ancillary services. All electrical equipment, such as transformers, rectifiers, air extractors, and refrigeration plants, are of the most recent standard currently available. An air treatment system ensures a moderate temperature with a comfort zone of temperatures (24 °-30 °C). The system supplies fresh air and extracts the stale air. The modern systems of fire detection and fire resistance equipment can be applied automatically and manually.

The grant total cost of Phase One (28 km) of the regional line amounted to 650 million Egyptian Pounds (1982 rates: 1 U.S. dollar = 1.35 Egyptian pound). It was completely financed by the Egyptian government. The foreign currency was obtained by special loan arrangements with the French government. Benefits of the Project The regional line has a capacity of 60,000 passengers per hour in each direction. This great improvement in traffic flow has without doubt resulted in the improvement of surface traffic in the congested area of the central city. From an economic point of view, the commercial speed of both public and private surface transport have improved, resulting in both energy and time savings that will be applied in the workplace, thus increasing productivity. According to several studies, the annual revenue from the system can be estimated on an economic basis to be 21% of its cost, when the line is operating at its maximum designed capacity. In addition to the economic benefits, a number of social and environmental benefits have been achieved. The in-

TUNNELLINGANDUNDERGROUNDSPACETECHNOLOGY 281

GUIDE ,,~ ~ ' WALLS

STAGE (11

{2)

(3)

(4)

(5)

%"NO

PLUG SLURRY

STAGE

TRENCH

I N S T A L L A T I O N OF THE PRECAST WALLS

(6)

GROUTING

(7)

• s/I//s

/ ,,/s/,'/,'.

EXCAVATION AND BRACING S T E P { I )

EXCAVATION AND BRACING STEP (2)

(8)

(9)

1 ROOF FINAL

~RAFT

LOWER BRACIN(

EXCAVA" LEVEL

BRACING, STEP (51

C A S T - I N - PLACE R.C. RAFT

C A S T - - I N - - PLACE R.C. ROOF

FINAL CONFIGURATION

Figure 3. Construction procedure for cut-and-cover tunnelling (open excavation) used on the Cairo metro.

work had to be performed without any restrictions of the traffic on the flyover. Another potential problem involved the construction adjacent to the Archaeological Museum, which required monitoring of vibrations. Also of concern were instances of the tunnel touching the foundation of the adjacent buildings. Finally, phasing traffic in order to access the job sites was a challenge.

of the platforms and ticket halls are decorated in the style of the walls of the Sakara temple. The ancient Egyptian arts are represented by famous statues and frescos beautifully distributed in the station, creating an atmosphere reminiscent of ancient Egypt. Mobarak station (Fig. 5) is characterized by the Islamic style, which is

emphasized by its blue color, by the Islamic Star pattern (the design of which and distribution of its colors differs in each location), and by the colored glass lanterns in the ticket halls. The three other underground stations have modern simple interiors, individualized by the distribution of the station logo on the walls at differ-

Interior Design of the Underground Stations The architectural design concept was prepared by a special committee of Egyptian architects and interior designers selected by the National Authority for Tunnels (NAT). The design aimed at emphasizing Egyptian styles and ensuring the coherence of materials and items used to facilitate the maintenance and identification of the stations. Each station was to be designed to have its own style and identity, while achieving a sense of homogeneity with the styles of the other stations. This was achieved by displaying the special logo of each station on the cream-colored walls used in all the stations. The lighting, the seats, the flooring, etc., were also planned to be uniform throughout the stations. Sadat station is characterized by the Pharaonic style (see Fig. 4). The walls

282

Figure 4. Sadat station is decorated in the Pharaonic style.

TUNNEU-INGANDUNDERGROUNDSPACETECHNOLOGY

Volume 4, Number 3, 1989

crease in comfort, safety and beauty of the surroundings, and the decrease in pollution and noise are examples of these benefits.

Conclusions Inauguration of the first line of the Cairo Metro is a milestone for the city of Cairo, which is the first city in Africa and the Middle East to adopt such a modern means of transport. The metro is operating very efficiently, transporting 400,000 passengers per day. Phase Two of

Volume 4, Number 3, 1989

the regional line (14.5km), which was completed in spring 1989, has brought the total length of the metro line to 42.5 km, and has increased the number of passengers to 800,000 per day. Cairo citizens have gained confidence in their daily dealings with modern equipment and arrangements on the line. The studies for the second line (Urban 1), which were completed in 1978, will be updated in 1989 to determine the major changes that occurred since then, and how these changes will affect planning and design for the Urban 1 line. []

References Project documents and reports. Parties involved in the project: Client: National Authority for Tunnels (NAT). Consultants: • Arab Consulting Engineers (ACE), Egypt. • French Society for studies & urban realisations (SOFRETU), France. • Transmark, U.K. Contractor: Interinfra-Arabco (Consortium of French and Egyptian Companies)

TUNNELLINGANDUNDERGROUNDSPACETECHNOLOOY 283