As one of the first and largest design and build projects of its kind in South Africa, the Gautrain Rapid Rail Link (Gautrain or GRRL) has been a pilot scheme in many respects.
Having been fast tracked to facilitate broader infrastructure expansion and 2010 World Cup construction goals, its two-phase development started in September 2006 and is scheduled to finish by the end of March 2011. Typically a state of the art rapid rail system of this magnitude could take up to 14 years to build.
HHO Design & Construct
Donovan Hugo, Director and Project Manager at HHO Africa Consulting Engineers says, "It is new for South African consultants to work on design and construct with the just in time design requiring you to modify and optimise as you go along."
HHO Africa in joint venture with Ingerop were appointed to undertake the preliminary design of two of the Gautrain Rapid Rail Link design sections, Marlboro to OR Tambo International Airport and Eeufees to Pretoria to Hatfield followed by the detailed design and construction monitoring phases for the 8.1km route from Eeufees to Pretoria and Pretoria to Hatfield.
Temporary Piled Wall With Traffic Above|
Their 40 month contract includes work on the most technically complex sections in terms of space constraints as the majority of the route has to be designed and built within a 12 m wide and 8m deep cutting, bordered on the one side by residential and commercial properties, and on the other by an operating South African Rail Commuters Corporation line (SARCC - actually now PRASA).
Says Hugo, "The design of the linear works was very challenging, particularly from Pretoria Station to Hatfield as the Gautrain Rapid Rail Link had to be fitted in next to the SARCC, all within the existing rail reserve. The Gautrain has to pass thru 5 operating Metro railways stations, resulting in careful planning of the construction activities, as the trains and stations had to be operational for the duration of the construction. In order to thread the GRRL through the existing urban infrastructure, 6.4km of earth retaining walls, 3 viaducts, 3 rail-over-rail flyovers and 18 other bridge structures are required. Wherever possible precast M beams have been used for the bridge superstructures for fast track construction. There are 11km of precast beams, 230km of pre stressing strands and 1600 rubber bearings.
Technology & Software
"We used Civil Designer software for the rail and road alignments and to calculate the earthworks profiles. We also determined the details of the various types of earth retaining walls as well as rail clearances. At most sections there was only 200mm clearance. The surveyor on site also used Civil Designer which made the interchange of alignment and designer files so much easier."
Section of the 250m Long Portal|
HHO, who were appointed in September 2006 were involved in the review of the preliminary design, draft design, draft construction and construction design phases. Says Hugo: "We had regular meetings with the contractors as well as design review meetings. It has been an iterative design process taking into account many elements, like cost and constructability."
Phase 1 of the Cut and Cover|
During the preliminary design phase the HHO project management team looked at various options for part of their section of the Gautrain (Cut and Cover 6) that passes underneath the Ben Schoeman highway.
Cut & Cover
The Ben Schoeman Highway, where the N1 transfers traffic from Johannesburg to Tshwane, carries 300 000 vehicles per day and is purported to be the busiest stretch of road in South Africa. Taking traffic accommodation into account was an important consideration in their decision to use the cut and cover tunnelling method on this portion of the Gautrain project.
This involved building a temporary 3 lane bypass in order that the rail crossing below the highway could be trench excavated for the construction of the in situ tunnel portals. While the rock underneath the highway was being excavated, lateral supporting pillars (18m exposed depth) were put in place to stablise the road and prevent the trench from collapsing. This way traffic flow could continue undisturbed on the temporary deviations.
To achieve this stability, HHO used temporary anchored piles. Says Hugo, "As we went down, we had to put anchors in to keep the piles back. We would then monitor the deflection of piles to check for any lateral movement. We constructed the portals in situ and then reinstated the road using vertical reinforced earth panels and backfill."
Hugo worked closely with the software programmers at Knowledge Base (the developers of Civil Designer) to customise the alignment functions specifically for the Gautrain project.
Says Hugo, "We've learnt a huge amount in terms of document control and managing the design process as well as co-ordinating the project management aspects. It comprises all aspects of Civil Engineering and is one of the most challenging projects we have done to date."
Gautrain & Rail Transport Future
Rail transport will enter a new era with the opening of the Gautrain and will introduce a modern inner-city commuter rail service connecting Johannesburg and Pretoria, with six trains per hour running at 18 hours per day between the two cities at speeds ranging between 160 and 180km per hour.
Travelling time between Johannesburg and Tshwane will be approximately 35 minutes and 12 minutes between Sandton and Johannesburg International Airport.
There are mixed projections on how effective the Gautrain will be in alleviating congestion, however James Chakwizira, Senior Researcher at the CSIR Built Environment says, "Gautrain is not meant to be a substitute for road based transportation and was never conceived as an alternative to urban mass public transport. In a way, the Bus Rapid Transit (BRT) proposal and initiative answers to that call as well as complementing the Gautrain project."
Says Chakwizira, "It is important to also view the Gautrain rapid rail link line as a starting point and line from where other lines and extensions are to be developed. This lends credence to the concept of Gautrain as the anchor rail line from which an inner and outer ring rapid rail link lines would integrate with the mass transport system in the Greater Johannesburg Area."
Public transport relies on densification to make it work and the future land use patterns around the station will be central. The Gautrain project office is working with municipalities to create station development plans around the 10 stations and is actively promoting land use change around stations, much of which is presently underdeveloped.