July 5, 2007
By Lucille Davie
ITS taken Gautrain officials just nine months to spend R5,8-billion, about a fifth of their R25-billion budget. That leaves R20-billion to be spent over the next three-and-a-half years.
But, says project leader Jack van der Merwe, much of the basic equipment needed for construction of the 80km high-speed train has come out of that expenditure. Some R681-million is being spent each month.
The tunnel entrance at the Marlboro portal is 11m wide and 7m high
One of the biggest pieces of machinery required for the construction is the tunnel-boring machine (TBM), which will arrive from Germany in October. It is to cost about R180-million. It weights 885 tons, is 160 metres long and is driven by seven motors with 150 teeth used to excavate soft rock. It will be used to dig a 3km tunnel of 6,8 metres in diameter at 30 metres below the surface at Rosebank.
Whereas other tunnels have been excavated by means of drilling and blasting, the "poor rock conditions" at Rosebank, with waterlogged soil, are not suitable for this method.
"Tunnel boring is a physically safe and an environmentally sound method of tunnelling, especially in built-up areas. This method does not disturb surrounding soil and it produces a smooth tunnel wall that is cost-effective," according to a Gautrain statement.
The tunnel borer
The TBM works by means of a rotating cutting wheel that cuts its way into the ground. Inside the wheel is a chamber where, by means of a conveyor belt, the soil is extracted and discharged to the opening of the tunnel into tipper trucks. While the machine advances at 1,5 metres, its rear end starts lining the walls of the tunnel by means of pre-cast segment rings forming a watertight concrete cylinder just behind the cutting wheel.
Thus, as the TBM moves along, it creates each complete tunnel section.
The tunnel at the Marlboro portal, where the train splits and goes to Tshwane and OR Tambo International Airport, is now 322 metres from the opening. On its way to the Sandton Station, it is being excavated at 10 metres a day.
The excavated rock is removed by dump trucks and is taken to a central crushing plant east of Linbro Park. Once crushed, it is stored in stockpiles until it is needed for filling material.
The tunnel, reaching to Park Station, is to be 15 kilometres in length. A small shrine, dedicated to St Barbara, the patron saint of tunnel workers, has been placed at the entrance to the Marlboro portal tunnel. The shrine and its burning candle were brought by the French engineers from a Catholic shop in France. Rosebank, Sandton and Park stations will also get a St Barbara shrine, as soon as tunnelling begins at these locations.
St Barbara was accepted during the Middle Ages as the patron saint of artillerymen, miners, tunnel workers and firemen. It is believed she protects against accidents, especially underground where explosives are taking place.
Work has started on the Rhodesfield Station, the station just before the airport - 94 houses along Fitter Road have been demolished. Road diversions will soon be implemented at Proctor and Kimmerling roads, which are being widened, with new cul-de-sac interchanges to be put in place. Three viaducts, or bridges, are to be built for this station.
The Gautrain station at the airport will be integrated within the airport terminals and will not be a separate building. Passengers will be able to get to the airport via the Sandton Station, a trip that should take about 15 minutes.
Park Station
Work continues on other stations. At Park Station traffic will soon be diverted to Smit Street, with full closure of Wolmarans Street. This is to create a support base for the 25m vertical shaft that is being excavated, with the last five metres almost complete. Once this level has been reached, the underground tunnel towards Rosebank Station will begin.
A concrete plant has been erected on site, where all the concrete required for the construction is prepared.
Rosebank Station
The vertical shaft at Rosebank Station has reached a depth of 20 metres, with three metres to go. Once this depth has been reached, a horizontal tunnel towards the Sandton Station will begin. The deepest section of this tunnel will be 96 metres.
Screen hoardings of five metres have been erected around the site to reduce noise generated by construction, and an irrigation system along the fence is being used to minimise dust pollution. A pedestrian bridge over Oxford Road gives a view into the construction site.
Sandton Station
Excavation of the underground station and parking area at Sandton has begun.
The vertical shaft at nearby Mushroom Farm has reached a depth of 31 metres. Now two tunnels one to Sandton, another to Marlboro will be excavated.
Meanwhile, the Tshwane area, where three stations Centurion, Pretoria and Hatfield are to be constructed, has been surveyed and work on viaducts has begun. Search and rescue operations at the Salvokop Nature Reserve will be conducted. Indigenous medicinal plants have been relocated to botanical and private gardens, nurseries and private collections. Snakes and other reptiles have also been rescued.
Jobs generated
By the end of April, 2 697 people were employed by Bombela and its sub-contractors. More than 93 percent of them are local, 366 are women and 2 491 are unskilled or semi-skilled workers. Some 11 percent of these women are in management positions.
The first phase of the high-speed train between Tshwane and Johannesburg and the airport is due to be complete in 45 months, making the completion date June 2010, the same month as the start of the football World Cup. The second phase, linking Midrand to the Tshwane stations, will be complete by March 2011.
Van der Merwe admitted the schedule was one to two weeks behind. "We will know closer to the end of the year whether we should accelerate operations."
Motorists are asked to call the Gautrain toll-free number - 0800Gautrain or 0800 428 87246 - to report any major incidents and to get more information.
Permission to use web site material
Publishers may use material from this site free of charge, as long as:
- Credit is given to either the "City of Johannesburg website
(www.joburg.org.za)" or to "Johannesburg News Agency
(www.joburg.org.za)";
- If the article is used online, a link is provided to the original
article on this website;
- The name of the article's author is acknowledged;
-
The webmaster is informed of how and where the material is used (fill
in this brief online form).
Johannesburg News Agency is operated by BIG Media at 011-484-1400 |
