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Tunnelling for Metro Rail in MEA: Current scenario and future outlook [free access]

July 1, 2018

Tunnelling is gaining prominence in the Middle East and African (MEA) region and investments of over USD300 billion are planned in various infrastructure projects across various sectors, including metrorail. 

 

Currently, metro projects covering total length of about 550-km are under-construction and these involve investment of over USD52 billion, Further, metro projects covering over 240-km are under planning. 

 

Tunnels in operational urban rail systems

  

Most of the metro rail systems in the MEA region have a mixed alignment and almost all metro systems have an underground section.

 

Table 1 provides details of the operational metro rail systems with underground tunnel sections.

 

Table 1: Tunnels in operational metro systems

Line

Total length (km)

UG* length (km)

Total stations

UG* stations

Project cost (billion)

No. of TBMs**

Dubai Metro 

Red Line

52.1

5

29

4

USD7.6

3

Green Line

22.5

8

20

5

Algiers Metro

Line 1

18.7

17

19

18

EUR1.1

NA

Cairo Metro

 

Line 1

44.3

4.7

35

5

EGP2

Not applicable

Line 2

21.6

12

20

12

EGP9.7

1

Line 3 Phase I

4.3

4.3

5

5

EUR0.53

1

Line 3 Phase II

7.7

4

5

2

EUR0.44

1

Tehran Metro

Line 1

42

26.4

29

24

NA

NA

Line 2

32

24.6

26

21

NA

NA

Line 3

37

37

28

28

NA

NA

Line 4

22

22

19

19

NA

NA

Line 7

27

27

22

22

NA

NA

Shiraz Metro

Line 1

22.4

22

21

20

NA

NA

Total

353.6

214

278

185

-

-

Note: NA – not available

*UG – underground

**TBM – tunnel boring machines

Source: Global Mass Transit Research

 

Of the total 353 km of existing metro rail length, over 60 per cent (214 km) is underground. The Iranian metro projects (Tehran and Shiraz metro systems) account for 74 per cent of the total underground metro rail length (214 km).

 

Dubai Metro Red and Green Lines as well as Cairo Metro Lines 2 and 3 deploy single-tube double-track tunnels.

 

The tunnels have deployed either slurry TBM or earth pressure balance (EPB) TBM because of their ability to safely excavate under urban areas that have soft soil and high pressure groundwater.  

 

Germany-based Herrenknecht has supplied the TBMs for Cairo Metro Line 2 and Phase I of Line 3 and France-based NFM Technologies has supplied the TBMs for Cairo Metro Line 3 Phase II. These are the two key suppliers of TBMs in the MEA. Mitsubishi has supplied the TBMs for Dubai Metro.

 

Tunnels in metro projects under construction

 

Seven metro rail projects, with total length over 549 km, are under-construction and scheduled to commence operations between 2020 and 2022.

 

Table 2 provides details of the underground metro projects that are under construction. 

 

Table 2: Tunnels in metro rail projects under construction   

Line

Total length (km)

UG length (km)

Total stations

UG stations

Tunnel type

No. of TBMs

Avg. rate of excavation (metres per day)

Supplier of TBM

Dubai Metro

Red Line extension (Route 2020)

15

3.2

11

2

Single tube double track tunnel

1

10

Herrenknecht

Riyadh Metro

Line 1

39.0

17.5

26

NA

Single tube double track tunnel

4

14.3

Herrenknecht

Line 2

25.3

3.0

16

NA

Twin tube

Not applicable

Not applicable

Not applicable

Line 3

40.9

6.2

22

8

Single tube double track tunnel

1

NA

NFM Technologies

Line 4

29.6

6.0

8

NA

Single tube double track tunnel

7

30

Herrenknecht and NFM Technologies

Line 5

13 .0

13.0

11

11

Line 6

30.0

8.5

8

NA

Doha Metro

Phase I

85

69

37

33

Twin tube

21

30

Herrenknecht

Algiers Metro

Line 1 extension B1

9.5

9.5

9

9

NA

NA

NA

NA

Tel Aviv Light Rail Transit (LRT)

Red Line

21

12

34

10

Twin tube

8

10

China Railway Engineering Equipment Group Company Limited

Tehran Metro

Line 6

31

31

27

27

NA

NA

NA

NA

Cairo Metro

Line 3 Phase III

17.8

9.3

15

8

NA

NA

NA

NA

Line 3 Phase IV

18.1

11.7

15

10

NA

NA

NA

NA

Line 4 Phase I

18

18

17

17

NA

NA

NA

NA

Total

549.2

208.7

244

151

-

-

-

-

Source: Global Mass Transit Research

 

Of the total 549-km metro rail network under construction, only 38 per cent (208 km) is underground and the remaining 62 per cent (341 km) is either at-grade or elevated. The share of underground section in metro projects with mixed alignment ranges between 10 per cent and 50 per cent.

 

Most of the projects have used single-tube, dual-track type tunnels primarily because of their lower construction and operations cost as compared to a twin-tube type tunnel, which are particularly useful for long-distance tunnels.

 

EPB TBM has been primarily deployed for tunnel excavation, whereas the cut-and-cover method has been used for the construction of underground metro stations. The average rate of excavation ranges between 10 and 30 metres per day.

 

Herrenknecht and NFM Technologies continue to be the two key suppliers of TBMs in MEA. 

 

Key issues and challenges

 

Figure 1 provides information about the key issues and challenges faced by developers of underground metro rail projects in tunnel construction in the MEA.

 

Figure 1: Key issues and challenges in tunnel construction in MEA

image001_1217

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                            

Source: Global Mass Transit Research

 

Best practices

 

One of the important practices followed by the MEA countries in the tunnelling projects is to combine the design and build contracts together and award it to a single consortium. This practice expedites the design, manufacturing and delivery of TBMs.

 

The design consultants conduct the geotechnical studies and provide information about the expected sub-surface conditions to the construction contractor, who in turn shares the information with the TBM supplier. With a single consortium managing these aspects, information flow is smooth and quick. Therefore, the TBMs can be delivered quickly.

 

 Conclusion

 

The metro rail tunnelling market has huge potential in the MEA because of rising population, increasing demand for public transport and shrinking city space for aboveground construction. However, going forward, financing can be an issue because most upcoming metro rail projects are underground and underground construction costs significantly more than aboveground construction.

 

Although the MEA region accounts for just 4.2 per cent of the global tunnelling market in 2018, it has recorded 300 per cent growth between 2013 and 2016. The growth has occurred primarily in Iran, Saudi Arabia and Qatar because these countries have invested extensively in road and rail tunnelling projects.