Ce1999 Cairo Metro

Construction of Cairo Metro Line 2 A. Madkour, M. A. Hudson, BSc, CEng, MICE and A. Bellarosa A new 30 km underground railway line is being built in the heart of Cairo, one of the world’s largest and fastest growing cities. Cairo Metro Line 2 will link the pyramids of Giza on the west bank of the Nile to central and northern Cairo on the opposite bank when completed in 2001. This paper briefly describes the methodology used for construction of the 18 stations, tunnels and workshop which make up this US$2 billion project—including the first ever tunnel under the Nile. A number of innovative solutions were developed to solve the problem of water leakage during construction.

Cairo is one of the largest cities in the Middle East and the population reflects Egypt’s ancient cultural heritage and diverse society. Egypt has been called the ‘mother of the world’ and has a recorded history, over five millennia, of large public works projects. The pyramids are renowned as one of the seven wonders of the ancient world and varying forms of pyramid stretch along the west bank of the Nile from Cairo as far as Nubia in northern Sudan. Many other monuments from early periods of history remain and artefacts continue to be found. Relatively more recent historical monuments in Cairo include the churches on the route taken by Mary, Joseph and Jesus on the flight to Egypt, the citadel of Saladin and the Khan El Khalili, an ancient souk which is still in use. Greater Cairo’s population is rapidly increasing and is expected to exceed 23·9 million in the year 2012. The present population is now estimated at 18 million and is densely packed into a city, forced by the surrounding topography to expand along the Nile River banks. Before completion of the Aswan dams, the Nile River cut high escarpments into the sandstone underlying the alluvial sands and these have acted as barriers to the expansion of the city. The urban transportation corridors therefore follow a north/south corridor in order to reach the centres of highest population density. Greater Cairo’s metro network was principally planned to increase the mobility of the people of Cairo and, in addition, to improve population mobility. The metro was also planned to reduce the growth in private car ownership. However, car growth has rapidly exceeded earlier estimates in parallel with the economic growth recently experienced by Egypt. Construction of the first metro line was completed in the 1980s. This line upgraded two existing suburban railway lines to metro standards. The city, prior to 1980, had an existing north/south suburban railway line to the north of the city and a similar line to the south separated by the city centre. The north line was operated using diesel locomotives while the south line was operated using elec-

trically powered vehicles with a catenary system. To complete Line 1, these independent railways were connected by cut-and-cover tunnels with underground station construction in the centre of the city, and power was supplied to the vehicles by a full catenary system. The number of passengers using Line 1 has constantly increased and 1995 studies recorded that the Line 1 passenger count was 328 million passengers a year with an estimated passenger count of 530 million passengers a year anticipated for the combined Line 1 and Line 2 operations by the year 2000. Line 1 operational expenditure including depreciation in 1994/95 was greater than revenue from Line 1 operations by a factor of approximately two, resulting in a deficit which continues to be borne by the Egyptian Government. Ticket prices today cost an average of 50 piastres for a single journey (£0.10) and the main expenditure is for the cost of depreciation of assets. The newest line (Line 2) also lies along the city’s north/south corridor but for the first time connects the east and west banks of the Nile in bored tunnel. The successful tenderer for the underground civil work construction for the first phase of Line 2 was a joint venture of French and local contractors led by Campenon Bernard (SGE) France. However, a separate local contract was provided for the civil works for the at-grade and elevated sections in the first phase. The project consultant selected by the client for the design review and construction services was a joint venture of international and local consultants formed under the title of Greater Cairo Metro Consultants (GCMC) and led by Parsons Brinckerhoff, USA. Construction of Line 2 commenced on 12 June 1993 and operational testing of the first section, phase 1A, was scheduled to start 40 months later and phase 1B in the following year. Phase 1A and phase 1B have both met these targets. The next phase (phase 2A) of metro construction on the west bank of the Nile is also complete. The lessons learned on the first phase have been integrated into the project management system to the

Proc. Instn Civ. Engrs, Civ. Engng, 1999, 132, May/August, 103-117 Paper 11668 Written discussion closes 15 November 1999

Keywords: transport planning; rail & bus stations

A. Madkour works for the National Authority for Tunnels in Egypt

Malcolm Hudson works for Parsons Brinkerhoff Europe

Aldo Bellaros works for Estp/Chebap Eiffage in France

103

MADKOUR, HUDSON AND BELLAROSA extent that completion of the phase was achieved well ahead of schedule. The first train run on phase 2A was actually carried out in early October 1998 for a visit to the project by the prime minister and his cabinet, but this was not part of the testing and trial running programme for the project.

Kaliobia Workshop Shubra El-Kheima

El Marg

Cairo Airport

Koleyet El-Zera'ah El-Mazalat El-Khalafawi

Description of Line 2

St Thereza

Fig.1 shows the two existing north/south lines with station locations and the proposed new Line 3 which connects the area of highest population density through the centre of the city to the airport in the north. Line 2, the line now under partial operation and construction, commences at grade as phase 1A in the north of Cairo at Shubra El Kheima and enters the underground section of the line north of Mazallat Station and continues underground, south to Mubarak Station in the city centre (Fig.2). Phase 1A also includes the workshop. The next section, phase 1B, is situated in the city centre and is totally underground between the two interchange stations (Mubarak and Sadat Stations ) completed during Line 1 construction. Phase 2A connects from the existing Line 1 Sadat Station and crosses under the Nile to Cairo University on the west bank. The final phase of Line 2, phase 2B, includes an elevated/at-grade section and connects south of Cairo University and terminates near Giza. Table 1 shows general project route information.

Rodel Farag

Imbaba

Massara Mubarak

Giza Gezira

Attaba

Sadat

Abdeen

Behoos Cairo University

Cairo

Giza Square Giza Station

Giza Suburban

Line 1 (42.5 km) Line 2 (30.5 km) Proposed Line 3 (30.0 km) rN ve Ri

ile

0

Scale of km

5

Contract programme The contract duration and phasing of completion of the workshop buildings, from start of detailed design to final handing over for operation, were based on train deliveries, storage requirements,

Helwan

Fig. 1. System map

Fig. 2. Profile of Line 2 Shubra El-Kheima

Koleyet El-Zeraah

Ismailia Canal Khalafawi

Mazallat

+20

St Theresa

Rod El Farag

Masarra

Mubarak

Attaba

Abdeen (M Naguib)

Sadat (East)

0 Phase 1A Cut-and-cover tunnel

River Nile

+20

Sadat (West)

Gezira (Opera) Dokki Behoos

TBM shaft

Cairo University

Bored tunnel

Stations

0 Phase 2A

104

Phase 1B

0

Scale of km

2

CAIRO METRO LINE 2 Table 1. Project information Greater Cairo metro line 2 project information International contractor’s works Phase

Start station name

End station name

Number of stations U: underground A: at grade E: elevated

Bored tunnel length: m

Cut and cover tunnel length: m

Phase total length: km

1A

Shoubra El Kheima

Mubarak North

5U

3454

1270

8

1B

Mubarak South

Sadat East

2U

2478

0

3

2A

Sadat West

Cairo University

3U 1A

3458

470

5

2B

Cairo University

Giza Suburban

2A 1E

0

0

2.5

Table 2. Contract information Greater Cairo metro line 2 contract information Phase

Duration: months

EWP: months

Status

Workshop Stage 1 Stage 2 Stage 3

27 36 48

0 0 0

In operation In operation In operation

Phase 1A

36

3

In operation

Phase 1B

48

3

In operation

Phase 2A

49

2

Completion achieved 12 months ahead

Phase 2B

35

2

In progress

EWP – Experimental Working Period

training, testing and maintenance requirements in advance of the train trial running dates. The contract durations for phases 1 and 2 are shown in Table 2. At the completion of each phase a short ‘experimental working period’ (EWP) was carried out to ensure integration of all systems including train running, safety of the line and also to provide for a training period for operations staff. The later phases of the project necessitated complex staging requirements at terminal stations where the operating line was extended to the new line. Wherever possible the operations complexity was minimized by commencing line operation on short completed sections of the new phase in advance of its total length.

Geology Line 2 soil profile consists of man-made fill, silty clay/clayey silt, interbedded clay silt, and sand and alluvial sands. The soil profile under the main branch of the Nile is shown in Fig. 3.1 The groundwater regime comprises a perched aquifer recharged by leaking city water supply pipes and

drainage pipes and a lower aquifer confined within the sand deposit beneath the silty clay/clayey silt layer. Piezometric pressures in the confined aquifer are generally about 3–4 m pressure head less than ground level and generally are affected by Nile River water levels.

Construction methodology Safety The contractor was required under the terms of the contract to submit its overall health and safety procedure for the works during the initial stage of construction. The initial procedure included a work breakdown analysis and this was used to assess the types of work expected for each site and to identify, for areas of risk, detailed procedures that needed to be submitted. It also proposed safety staffing levels required for these areas and also for the whole of the works. The safety staffing levels were also based on the anticipated numbers of workers per month at each site including back-up sites, laboratories, batching plants and at the off-site production factories.

105

MADKOUR, HUDSON AND BELLAROSA Fig. 3. Nile crossing: section looking south

Bed protection

River Nile East branch

River Nile West branch

+20 +10 0 -10 -20 -30

yyyyyyyyyyy @@@@@@@@@@@ €€€€€€€€€€€ ÀÀÀÀÀÀÀÀÀÀÀ ,,,,,,,,,,, y,À€@,, yy ÀÀ €€ @@ @@@@@@@@@@@ €€€€€€€€€€€ ÀÀÀÀÀÀÀÀÀÀÀ ,,,,,,,,,,, yyyyyyyyyyy y,À€@ @@ €€ ÀÀ ,, yy @@ €€ ÀÀ ,, yy Gezira Station

To Sadat Station

Bored tunnel

Bored tunnel

0

100

Fill

200

300

Clay

To Dokki Station

400

500 600 Scale of m

Micaceous Silty Sand

Specific authorities were defined for all staff on the project and the safety officer was authorized to issue instructions to stop the works if any safety violations were observed. In addition, safety training and reporting requirements were defined, site medical facilities including site ambulance provision stated and the locations and telephone numbers of hospitals and other emergency services given. A site safety manual was also developed and was issued in Arabic to each worker on first arrival on the site. After agreements of the overall procedure, specific procedures were developed for activities such as tunnelling, diaphragm walling, tower cranes, excavation and strutting installation and removal. In addition, as the works progressed, new procedures were developed to accommodate changes in the working methods. In the initial stages of the work, the incidence of accidents was statistically significant and, regrettably, the gravity rate increased. This is considered to have occured due to a lack of familiarity of the site labour force with the new methods adopted on the project. The metro accident rates cannot, however, be directly compared with accident rates in other countries due to differences in working practices in Egypt. As the project work load increased and the gravity rate increased, attention to safety standards was reinforced by the contractor, the consultant and the client and maximum emphasis was placed on ensuring that all activities were carried out in the safest possible manner. To this end the contractor ensured that, not only specific health and safety procedures were prepared, but also all site procedures and method statements were developed specifically on the basis of safe methods of working. The contractor’s safety management, to ensure that the risk of injur y to the work force was minimized, assessed the procedures prior to issue.

106

700

800

Sand

900

1000

Gravel

Only when the safety management were satisfied with the proposals were the procedures issued to the client for approval. By using this system and dramatically increasing site training, the accident frequency subsequently reduced. Accident statistics for the project are shown in Fig. 4.

Environmental considerations Due to Cairo’s size and rapidly increasing population, severe problems are faced in provision of amenities for the population. Environmental considerations have, until only recently, been subservient to the achievement of economic growth. In the last 20 years, however, major projects providing improvements in water quality and sewerage treatment have been carried out and larger sections of the population now have these amenities. In addition to restrictions on discharge of water from construction sites, with discharge of untreated water to the Nile strictly prohibited, there are restrictions on heavy vehicle access to the greater Cairo area. Dumping of waste such as building debris and excavation materials, however, is largely dependent on private disposal services as the city services are extremely limited. Air pollution is, however, now attracting attention and studies are proposed to identify sources and recommend solutions to improve the air quality in Cairo. One action now being made is a reduction in the number of petrol-powered vehicles on the roads. This involves changing all taxis from petrol engines to natural gas with resultant lowering in polluting emissions. Works areas The works areas provided to the contractor required closure of main city thoroughfares and diversion of traffic onto other routes. At each station site, wherever possible, the full width of the street was closed to traffic and occupied by the contractor. This allowed the contractor to complete the

CAIRO METRO LINE 2

25

Work accidents

Fig. 4. Line 2 accident statistics

20

Rate

15 Average

10 5

By month

Apr-98

Jan-98

Oct-97

Jul-97

Apr-97

Jan-97

Oct-96

Jul-96

Apr-96

Jan-96

Oct-95

Jul-95

Apr-95

Jan-95

Oct-94

Jul-94

Apr-94

Jan-94

0

Months

30

Frequency rate

25

Frequency

20 15 Average 10 5

By month

Apr-98

Jan-98

Oct-97

Jul-97

Apr-97

Jan-97

Oct-96

Jul-96

Apr-96

Jan-96

Oct-95

Jul-95

Apr-95

Jan-95

Oct-94

Jul-94

Jan-94

Apr-94

0

Months

.45

Gravity rate

.40 .35 .30 Average

Gravity

.25 .20 .15 .10

By month

.05 Mar-98

Jan-98

Nov-97

Jul-97

Sep-97

May-97

Jan-97

Mar-97

Nov-96

Jul-96

Sep-96

May-96

Jan-96

Mar-96

Nov-95

Jul-95

Sep-95

May-95

Jan-95

Mar-95

Nov-94

Jul-94

Sep-94

Mar-94

May-94

Jan-94

.00

Months

station roof slab, avoiding the time and cost associated with provision of numerous variations in the traffic pattern. Immediately after the roof slabs were completed some limited traffic provision was made along or across the site to improve the situation for the local residents. As the civil works ended and the finishing works commenced the works areas were gradually opened again to traffic, usually by provision, initially, of one full lane in each direction which reduced the period of total road closure.

Utilities In general, all utilities were diverted prior to construction commencement; however, where large utilities, such as 220 kV cables and large diameter sewers and water pipes, could not be diverted special excavation techniques were used where these crossed the cut-and-cover tunnel works. At all stations except Rod El Farag Station all major utilities over the main station boxes were diverted and excavation was therefore unobstructed allowing efficiency of construction.

107

MADKOUR, HUDSON AND BELLAROSA Fig. 5. Workshop layout

To Metro main line (connects at Shubra El Kheima) 18 8

6

0

25

Scale of m

200

17 23

28 17

11

7

Connection to Egyptian Railways

24 16

12

17 19

20 22

Local contractor buildings 1. Office building 2. Office and technical building 3. Maneouvre cabin 4. Office and technical building 5. Training centre 6. Control and security offices 7. Maintenance dept workshop and storage 8. Maintenance dept office 9. Dangerous goods store 10. Water tank 11. Sewerage pump room International contractor buildings 12. Siding track hall 13. Light repair workshop 14. General overall workshop 15. Paint shop 16. Lighting and power stations 17. Switch cabins

28

3

1 13

11

2 14 21

27 14

16

4 15 15 9

5

11 26

18. Rectifier station 19. Bogie storage slab 20. Lathe pit/bogie changing hall 21. Light repair workshop for diesel locomotives 22. Train wash

24. Turntable 25. Local signal box 26. Test track inspection pit 27. Lifting table 28. Sump chamber

6

Fig. 6. Workshop panorama

Workshop The workshop was designed to accommodate 48 sets of eight car trains and, due to land constraints, was connected to the mainline by a single access track. The workshop is surrounded by a densely populated mixed-use industrial/residential area, which severely constrains the layout and track connection of the workshop to the main line. This limi-

108

tation requires that a shunting zone is located behind the first at-grade station. The layout of the workshop is shown in Figs 5 and 6 and clearly shows the limited site area. Prior to the start of the main contracts, advance works were carried out to level the site and install fencing. Local contractors, which were supervised by the National Authority for Tunnels (NAT), also

CAIRO METRO LINE 2 Fig. 7. Behoos Station long section

Accesses/air shafts

Roof plan

Cut-off walls

Long section

To Dokki

To Cairo University

0

carried out site formation, general earthing networks, utilities, roads and office buildings. The main workshop maintenance buildings, track and workshop equipment were carried out by the international contractors. The project consultants not only carried out inspection of the international contractor’s works but were also responsible for co-ordination between the local and international contractors. Civil works co-ordination commenced as soon as the works started and weekly co-ordination and progress meetings were held with critical problems reviewed at monthly site meetings chaired by NAT. As the works progressed and the site interfaces became more complex, working groups were set up to review and release constraints caused by the ever-increasing volume of construction. Eventually complex working and safety procedures were adopted to allocate track areas and rooms in buildings for equipment installation, vehicle delivery and testing, driver and personnel training, power requirements and defects repair. Stations The primary function of the stations during the civil works construction stage was to permit the unobstructed passage of the tunnel boring machine (TBM) through the stations. The main station boxes are generally rectangular in plan and were standardized within the limits of the right of way. This standardization led to the use of the same construction methods throughout the project and promoted efficient use of construction resources.

Scale of m

Fig. 8. Behoos Station cross section

25

Ground +20.0

Roof Ticket

Technical

Area occupied by tunnel

Raft

Soft gel plug

0

Scale of m

10

Toe level -25.5

109

MADKOUR, HUDSON AND BELLAROSA

Fig. 9. Attaba Station platform level

110

The station boxes have excavation depths varying from 15–23 m and have accesses and airshafts attached to the main box. See Figs 7 and 8 for Behoos Station layout. The platform length is 144 m and is designed to accommodate an eight-car train. The stations are designed to be fully watertight and this specification required the use of reinforced concrete diaphragm walls (of up to 1·2 m width) incorporating CWS stop-end joints.2 Fig. 9 shows a completed station at platform level (Attaba Station). The design of the diaphragm wall was based primarily on the loading applied during the construction stage. The depth of the diaphragm walls was also based on provision of a soft gel plug by injection through tube-a-manchettes to limit water inflow through the sand and avoid excavation instability. The soft gel plug was considered to impart no strength to the sand, therefore, the toe level of the diaphragm walls was controlled by the need to maintain the maximum safe economic weight of soil above the plug. The design of the diaphragm wall section was also based on minimizing settlements caused by wall deflections where excavation was carried out close to other structures. In a number of locations, hard gel plugs were provided where it was consid-

ered economic to improve the strength of the soil and therefore reduce the depth of the walls. In addition to diaphragm walls, bentonite/cement slurry walls were constructed to divide the stations into smaller boxes to allow sectioning of the excavation process. For more detailed explanations of the construction techniques adopted see references 3 and 4. The station raft slab was designed to act as a simply supported beam/strut. Horizontal loads were transmitted into the walls in bearing, but vertical ground water loads were directed into a line of corbels connected by couplers to the diaphragm wall. The permanent structure construction sequence finally adopted was as follows • • • • • •

complete the roof slab complete the ticket slab at the station ends complete the technical slab install two layers of strutting cast the first stage raft slab complete the break in and break out slurry walls and grouting • demolish the station concrete ends (tympan) for TBM transit. TBM transit through the station however post-

CAIRO METRO LINE 2 poned the full completion of the raft (second stage raft concrete), platform structure, columns, walls and ticket slab. The Line 1 interchange stations, Mubarak and Sadat, were constructed without provision for TBM transit and the Line 1 station boxes provided only sufficient space for platform, train and permanent equipment clearances. To complete the TBM drives and to allow for removal of the TBMs, short lengths of extension boxes were constructed on each end of Mubarak and Sadat Stations by diaphragm walling together with plug and jet grouted/injected box connections. In general, TBM progress was maintained throughout the tunnel drives but the station excavation depths were such that the plug and the TBM connection works occasionally suffered localized leakage that necessitated repair works, and this caused some delay to the TBM progress.

Three groutholes drilled into diaphragm wall +20.6

• Inclination of the grout holes caused by deviation in drilling verticality resulting in localized areas of low grout absorption. • Incomplete cutting of the tube-a-manchettes. A high-pressure water jet was used to cut the tube-a-manchette below the excavation level. The ability of the water jet to cut the pipes was dependent on the diameter of the nozzle of the jet and continued use of the tool gradually degraded the nozzle. During soil removal, the excavation equipment pulled out the tubes. If the tubes were incompletely cut, the grout tube could be pulled out for most of its length level causing a flow path through the plug. • Plug defects, which could not be explained by the above theories. At Dokki Station during excavation to the raft level of the central box a sudden inflow of water was observed which quickly exceeded the capacity of the pumping wells in the box. Immediately, the contractor commenced backfilling above the leakage area and installed relief pipes and surface pumps to pump water away from the leakage zone. Over the two days following the leak, several layers of soil surrounded by reinforced concrete were placed around the leakage area to provide mass back onto the excavation. The concrete surround was provided with a series of holes through the top

GWL

Nine casings installed through the station for well points +11.4 Technical slab

+6.9

First strut level

+4.0

Second strut level

Grout pipes

Typical water leakage problems experienced during excavation. During injection of the gel plugs, the contractor controlled grout take by sophisticated computerbased control systems. Records of volumes and pressures retained on the computers were compared with design volumes and pressures in every sleeve of the tube-a-manchettes. After completion of the injection a pumping test was undertaken to assess the final permeability of the soil. Occasionally there were a number of defects and these may have been caused by the following.

Roof slab

Concrete cover Raft slab

-1.0 120m3 of sand/ cement backfill

-17.7

Possible leakage hole -24.2

slab to permit installation of relief wells and standpipes (Fig 10). The contractor then carried out a number of experiments by alternating pumping from different wells and monitoring drawdown. The location of the leakage path was subsequently assessed to be immediately adjacent to the toe of the diaphragm wall. A new well was drilled and luckily this well intersected with the leakage point and instantly all inflow around the leakage area ceased. In addition to monitoring of existing piezometers inside and outside the box, a number of new piezometers outside the box were also installed. These provided more detailed information on ground water levels in the area of dewatering. The primary concern was that consolidation settlement could rapidly occur if the zone of dewatering extended to outside the box. In addition to the installation and testing of the new wells inside the box, the contractor, in parallel, completed the raft slab around

Fig. 10. Dokki Station leak repairs

111

MADKOUR, HUDSON AND BELLAROSA

Struts

Stage 1 Diaphragm walling

Stage 2 Plug injection Pump testing

Stage 3 Excavation/strutting Waterproofing Base slab

the leakage area, which helped to control the leakage by adding permanent loading onto the soil. Cut-and-cover tunnels The cut-and-cover tunnels were constructed in the same manner as the stations and to the same watertightness criteria except that the diaphragm wall retaining structure was used only for temporary ground support. Inside the diaphragm walls an arched tunnel structure of cast in-situ reinforced concrete was placed against and surrounded by a waterproofing membrane (Fig 11). In the transition zone between the at-grade and covered tunnel the permanent retaining structure was the diaphragm wall connected directly to the raft and roof slabs of the tunnel. Again to assist excavation and improve watertightness control, slurry walls were constructed to divide the tunnels into sections. Bored tunnels The tunnel lining comprises seven segments and a key, with the key introduced longitudinally to complete the ring. This therefore required an overlength on the TBM shoving jacks of 0·5 m. The lining is tapered with a nominal segment length of 1·5 m and

Stage 4 Strut removal Waterproofing Walls

112

Stage 5 Strut removal Waterproofing Roof

Stage 6 Waterproofing Backfill Strut removal

Fig. 11. Cut-and-cover construction method Fig. 12. Completed tunnel Attaba to Abdeen

CAIRO METRO LINE 2

Fig. 13. TBM at Behoos Station raft

Fig. 14. TBM break out at St Theresa Station

113

MADKOUR, HUDSON AND BELLAROSA

Slurry wall box

Station

TBM break out

Station

Jet

Jet grout

grout

Hard gel Soft gel

Initial break-in/out concept

Fig. 15. Breakout details

Soft gel

Revised break-in/out concept

width of 0·4 m, with internal dia. of 8·35 m. Joint waterproofing is provided by an elastomeric gasket supplemented by a hydrophilic seal. Fig. 12 shows the completed tunnel with walkway/20kV cable channels and also shows a connection to one of the off-line rectifier stations. TBM choice5 was based on the ability of a bentonite slurry shield to excavate the coarse granular material observed during the site investigation. In addition, choice was based on • previous experience of similar ground conditions • the need to closely control settlement • continuous grouting of tunnel segments. Slurry treatment plants were provided at the surface for the slurry returned from the excavation and for preparation of the fresh bentonite used for the excavation system. The plants were designed to separate soil particles from the bentonite supplied for face support by three stages • screening of particles • cyclone separation • concentration by use of a coagulation agent and pressing of the cake produced from the first two stages through a filter. Bentonite density at delivery to the TBM was stabilized at 1·1 t/m3 and was adjusted depending on the anticipated ground conditions. In general, bentonite consumption was 30 m3 per 1 m3 of excavated soil but, where the TBM progressed through areas of jet grout, the bentonite became rapidly contaminated resulting in continuous replacement of bentonite and subsequent problems with slurry disposal. The TBMs were articulated and were designed

114

to install the tunnel lining to the alignment’s minimum horizontal curve radius of 201 m. Surface ground settlement volumes were observed to average in the region of 0·5–1·0 % of face volume and the automatic continuous tail void grouting system was very successful in controlling surface settlement. The depths of the settlement troughs were normally observed to be in the range of 15–20 mm at ground level. The length of the TBM and the back up trailers was approximately 60 m and occupied over 40% of the station raft slab. This effectively restricted the completion of the station civil works at raft level until after the TBM had completely exited the station. Fig. 13 shows the TBM inside Behoos Station. The tolerance requirements of the specification for tunnel driving were 75 mm for alignment plus 50 mm for erection. The as-built survey information compared against the installation records for the lining showed that the tunnel linings were built to tolerance, but responded to the continuous automatic tail void grouting by ovaling at installation. This vertical ovaling was reduced by squat caused by ground loads developing on the lining. This contradicts the usual design assumption that the lining squats immediately after build. Two TBMs were provided to achieve the phase 1 programme targets. The machines, however, performed well beyond expectation6 and this resulted in the need to expedite the station construction programmes to avoid disruption to the TBM progress. On the basis of the driving rates achieved on phase 1, it was considered possible for phase 2A to drive a single TBM from the cut-and-cover works through the three underground stations. The tunnels under the Nile to connect to the interchange station at Sadat are complete and the TBM has again performed exceptionally well and transited through all three stations ahead of schedule. Breakout methods Fig. 14 shows the top of the TBM cutter head emerging after completion of the ground water balance breakout at St Theresa Station. The ground water balance method avoids a hydraulic gradient through the soil and was used where there was either insufficient space to construct a standard breakout or difficulties with provision of the proposed standard breakout. However flooding of the stations did cause delay to other works in the station and the ground treatment design was altered for subsequent breakouts to minimize disruption. Early breakout construction methods provided a plug of jet grouted soil,3 essentially as an unreinforced retaining structure in front of the station end walls. These end walls (tympans) were removed to permit the TBM to bore through the jet grout and enter the station. It became clear during early execution of these breakouts that jet grout alone could not be relied upon for ground water control as small discontinuities of untreated soil were encountered between the jet columns starting at depths of 15–20m

CAIRO METRO LINE 2 below ground level. Where these extended to the toe of the column or connected to the outside of the treated mass, leakage paths caused erosion and cavities with the danger of soil collapse to the surface. After some trial and error the final solution adopted was an unreinforced cement/bentonite slurry walled box with an impermeable chemically grouted hard gel base plug beneath the ground treatment, but still provided with a jet grout mass (Fig 15). Quality control The civil works specifications were based on European and Egyptian standards. The quantities of materials used were significant: almost 1500 km of drilling for grout injection, 350 000 m2 of diaphragm walls and 300 000 m3 of concrete. The completed works including watertightness requirements, despite the speed of construction, complied with the specification requirements. The bored tunnels, in every instance, complied with the specification and there were no leaks or dampness observed on the tunnel linings and joints. Details of the lining joint showing the installation of the ‘Phoenix gasket’ and hydrophilic seal are shown in Fig 16. Leakage, though small, was observed in the stations during excavation but the extent of leakage was controlled by injecting either a hydrophilic acrylic resin grout into the joints in the diaphragm wall structure or by structural repair. The locations of points of leakage were predominantly • leaks at the diaphragm wall joints • around the tunnel linings at the station connections

Fig. 16. Part section through tunnel lining at circumferential joint

Excavated surface

Tail void grout Hydrophylic seal Elastomeric gasket

Segment Waterproof concrete Groove for caulking

Inner face of lining

• at the raft/diaphragm wall connections. At the time of completion of the phase 1 stations the leakage was significantly reduced and the volume could not be accurately measured as other sources of water (i.e. washing) in the stations were in excess of the volumes which could be attributed to structure leaks. In any event, the contract called for only two criteria for watertightness for the stations. The first criterion, class 1, is for the diaphragm walls and structure and this required the structure to be completely dry; that is, no trace of moisture. The second, class 2, is for diaphragm wall joints

Table 3. Bored tunnel statistics Phase 1 (Six Day Work Week) Progress

Segment damage

Location Length: m

Best week: m

Average week: m

Average month: m

Average month including delays: m

Per cent damaged/ total segments per drive

Khalifawi to St Theresa

795

100

49

213

213

4·6

St Theresa to Rod El Farag

743

150

71

306

248

3·3

Rod El Farag to Massarra

888

135

58

240

148

2·6

Massarra to Mubarak

998

168

82

388

360

2·3

Mubarak to Attaba

740

205

125

543

291

1·2

Attaba to Abdeen

986

138

81

350

350

3·0

Abdeen to Sadat

683

170

117

422

422

0·5

Phase 2A (Five Day Work Week) Progress

Segment damage

Location

TBM Shaft to Behoos

Length: m

Best week: m

Average week: m

Average month: m

Average month including delays: m

Per cent damaged/ total segments per drive

468

135

93·6

456

456

2·28

Behoos to Dokki

1093

176

133·3

576

323

0·53

Dokki to Gezira

1089

194

108·9

471

450

Not available

Gezira to Sadat

858

197*

139·7

605

605

2·2

115

MADKOUR, HUDSON AND BELLAROSA 1994

1995

1996

1997

Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Jan Feb Mar Apr May

1993

Phase 1A Cut and cover/portal Ismailia canal crossing Hand mined tunnel Mazallat station Cut and cover Maz-Kha El Khalafawi

St Theresa station

Rod el farag station

Masarra station

Mubarak north station Phase 1B Mubarak south extension Attaba station

Abdeen station

Sadat east extension

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68

Construction programmes Stations and tunnels The phase 1 station construction programme in Fig. 17 shows the TBM duration and the track access dates for each section of the works. A typical station construction programme (Behoos Station) is shown in Fig. 18, which is part of the phase 2A works. The civil construction of this station was controlled by the TBM progress and the finishes were controlled by the speed of equipment installation. Bored tunnels The statistics for the tunnel construction are shown in Table 3. The weekly rates given are based on days worked/calendar days x length achieved. The driving rates between the Line 2 stations were variable and the delayed rates were assessed on days lost, usually awaiting availability of the station raft for TBM entry.

Civil works

Track access

Arrangements

TBM

Fig. 17. Phase 1 as-built programme Fig. 18. Phase 2A Lot 47: Behoos Station as-built programme

1

Injection of plug

2

Excavation

3

Roof slab

4

Technical slab

5

Strutting

6

Raft slab

7

Ticket slab

8

TBM Break out

9

TBM Break in

10

Access /Airshafts

11

Architectural works

12 13

116

Mar

Feb

Jan

Dec

Nov

Oct

Sept

1998 Aug

Jul

Jun

May

Apr

Mar

Feb

Jan

Dec

Nov

Oct

Sept

1997 Aug

Jul

Jun

May

Apr

Mar

Feb

Jan

1996

Diaphragm walls

that could be visually damp but no trace of water absorption was permitted on blotting paper laid on the damp area.

Trackwork The trackwork contract programme was based on continuity of access from one end of the project and, as the track installation progressed, the completed tracks and the track access was to be shared with follow-on contractors for cable pulling, equipment delivery and installation. Fig. 19 shows a section of concreted double track with rubber boots cast-in prior to third rail installation. On phase 1A, as the date of track access approached, several sections of the civil work were not complete due to complex technical difficulties associated usually with utility, works areas or water problems. Continuous access was therefore not available from the at-grade end of the works for material delivery. A decision was therefore made to allow the trackwork contractor to access isolated sections of the track via the station roof slabs for delivery of rail lengths, sleepers and equipment. The civil contractor was therefore required to interface its works with track access at the same location. As the trackwork progressed, follow-on contractors accessed the works and, as the works neared the operation period, access for daytime track concreting was usually shared with nighttime power cable pulling in the same sections of track. The dates for access to the works to commence track construction (Fig. 17) show the extent of discontinuous working required to maintain the track installation schedule in accordance with the project programme.

Conclusion The successful completion of the first phase of Line 2 was due, in large measure, to decisive project management by the National Authority of

CAIRO METRO LINE 2 Table 4. List of contractors and consultants Greater Cairo contractors and consultants Consultant’s team

Civil contractor’s team

Track contractor’s team

• Parsons Brinckerhoff (USA) — lead • Electrowatt (Switzerland) • Sabbour Associates (Egypt)

• • • • • • • • • •

• Cogifer Entreprise (France)—lead • Orascom (Egypt)

Campenon Bernard SGE (France)—lead Arab Contractors (Egypt) Dumez-GTM (France) Spie Batignolles T.P. (France) Bouygues (France) Dragages Et Travaux Publics (France) Eiffage (France) GTM International (France) Soletanche Bachy (France) Intertectra-BTP (France)

Fig. 19. Double track awaiting third rail

Tunnels, the contractors and the consultant. The management of the works by the team and the extensive co-ordination and planning efforts necessary to bring one of the largest public works projects in Egypt to a successful conclusion were assisted by the amicable working relationships which developed and were fundamental to the successful completion of the project.

Acknowledgement Members of the contractor’s and consultant’s groups engaged on Cairo Metro Line 2 works are shown in Table 4. The authors wish to express their thanks to D. Campo, D. Richards, J. Pearson, Y. Mizzi, P. Ramond, D. Rossignol and A. Sicre for their contributions to this paper and Yves Hadjaj for the use of his excellent photographs.

Dedication This paper is dedicated to the memory of Bernard Chartroux who was responsible for the civil works for Khalifawi, St Theresa and Behoos Stations.

References 1. RICHARDS D. P., RAMOND P., EZZELDINE O. Proceedings of the first bored tunnel crossing of the Nile River. Proceedings of the ITA Conference, Sao Paulo, Brazil 1998. 2. DUPEUBLE P. CWS system provides load bearing and watertight joints between diaphragm wall panels. Ground Engineering Magazine, September 1985. 3. CAMPO D. W., RICHARDS D. P., COUDRY M. A review of the grouting on Line 2 of the Cairo Metro. Proceedings of the Rapid Excavation and Tunnelling Conference, Las Vegas, USA, June 1997. 4. RICHARDS D. P., BURCHELL A. J., CAMPO D. W., RAMOND P. Review of break-in and breakout concepts for tunnel boring shields in saturated soft ground. Proceedings of the ITA Conference, North American Tunneling 96, Washington, DC., USA. 5. HERRENKNECHT M., MAIDL B. Transferring the European experience using Mixshields for the employment in Cairo. Proceedings of the Conference on Tunnelling and Ground Conditions, Cairo, 1994. 6. RICHARDS D.P., RAMOND P., HERRENKNECHT M. Slurry shield tunnels on the Cairo Metro. Proceedings of the Rapid Excavation and Tunnelling Conference, Las Vegas, USA. June 1997.

Please post/fax/e-mail your discussion contribution (up to 500 words) to the editor by 15 November 1999.

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