In his presentation Mr Van Ooteghem treated the Society to a feast of heavy and complex heavy civil, foundation and tunnel engineering. Like many of London’s stations, the Central station at Antwerp is presently a terminus, but now needs to be transformed into a through station in order to form a key part of the European high speed rail network.

Dirk began by reviewing the development of the Belgium high speed rail lines, the first of which came into use in 1994. Phases under current construction will see connections between Brussels and Köln added next year, with the 300km/hr line from Brussels through Antwerp and on to Amsterdam due for completion by 2005. The connection through Antwerp is to make use of the existing Central station. This requires a sub-surface alignment through the heart of the existing terminus and its approach, and a bored tunnel section beyond.

The construction of this north to south link includes:

  • works between the Berchem district of Antwerp

    and Antwerp Central station;

  • re-organisation of the Central station to accomodate the through trains at low level;

  • the construction of two tunnel tubes under the city north of the station, and associated works.

Berchem to Antwerp Central

The works between Berchem and the Central station commenced in 1997 and are well underway. The existing railway network is complex and heavily used, so the new construction poses many challenges. Major constraints included:

  • having to tunnel beneath and construct adjacent to numerous old buildings which are listed;

  • 70% of the existing rail traffic must continue to run normally throughout the duration of the works;

  • having to preserve three operational platforms initially on the west side of the station, and subsequently on the east side;

  • the requirement to retain the full surrounding road system, with the opportunity being taken to instigate a new one-way system.

The presentation was most impressive in describing the sheer diversity of civil engineering techniques being employed through this section of the works. Some of those described were very novel, and included:

  • inclined jet grouted piles through and below old foundations;

  • edge girder sheeted trenches;

  • side wall tunnels formed by trench sheeting;

  • nailed walls;

  • inclined excavations behind vaults;

  • temporary large diameter piles to support the

    eastern side of the new surface deck;

  • mining beneath the new deck to provide the

    space for one or two lower levels of new rail tracks.

Figure 3 shows how rows of inclined jet grouted piles were installed to strengthen and support the outside of the existing viaduct, and the listed vaults.

Further strengthening works to the side of the viaduct required the formation of sheet trenches with edge girders, as shown in Figure 3. Heavy girders then were put in place to support the arches. Also shown are rows of vertical bored piles installed to give temporary support to the eastern side of the new deck which will carry the high level rail tracks.

The need to install the new tracks at a lower level led to the construction of a nailed wall. Portions of the wall were constructed by means of sprayed concrete applied to reinforcement cages, a technique well known to tunnellers but much less common at the ground surface. With the ground level now able to be lowered, further inclined jet grouted piles could be inserted on the inside of the viaduct to strengthen its foundations, as illustrated. Also shown here is the yoke used with the temporary vertical piles.

With these measures in place it was then possible to excavate behind the vaults. Holes could then be bored to insert stress bars. This was followed by further excavation below the arches, and with the support in place as provided previously on the outside, it was possible to break out the spring line masonry of the arches to position new girders.

Stress bars were then placed, struts were clamped in the concrete and new girders finally positioned. The concrete deck which accommodates the new rail tracks was the final component of construction of these complex works on the eastern side, completed in June 2001. Now a similar sequence of activity has commenced on the western side. Once all this is accomplished mining can take place under the deck and the temporary piles can be removed, to provide the multi level approach to the station.

Not content with the detailed explanation of this highly complicated staged sequence of operations, Dirk’s presentation continued by describing the construction activities at the location of existing bridges at Areenstraat, Belgielie and Plantin en Moretuslei. In the vicinity of the three hinged iron arched Belgielie Bridge it has been necessary to construct diaphragm walls as deep as 33m, to form boxes to carry the new lower level rail tracks. The size of the reinforcement cages required these substantial walls to be fabricated off site in three sections. The propping to the excavations here was substantial, and it was decided to provide insulation around the steel props to minimise the significant movements of the shored ground which might otherwise occur due to the expansion and contraction effects of warming from the sun.

Antwerp Central Sation

Built over 100 years ago, the “cathedral like” architecture of Antwerp Central station had been inspired by the station at Lucerne, Switzerland, and its gothic dimensions feature a 75m high dome. Dirk explained how the works to provide the through station, which started in 1998, were the equivalent of giving the station its centennial overhaul, and he hoped that it would be a further 100 years before any further fundamental changes would be required!

For the reconstruction of Antwerp Central station, Dirk presented a number of artist’s impressions which demonstrated the spacious ambience being sought for this important transport interchange. He continued by describing the several phases of operation required for the development of the underground space. Three terminus tracks must remain in place at all times during these complicated operations. Eventually there will be no fewer than fourteen tracks at three levels, and platforms will be lengthened. Shopping facilities will be incorporated into the ground level area.

Construction activity has already started on the eastern side of the station beneath the main building. One novel and fascinating aspect of this work is the construction of a series of high level, closely spaced, small diameter bored tunnels, to provide a raft of pipes to support the foundations of the station building when excavation proceeds beneath. These will be employed in conjunction with extensive compensation grouting.

Bored Tunnels

Dirk completed his talk by describing the plans for the two 1200m long bored single track tunnels beneath the north of the city and the cut and cover emergence section beyond. Further works in this section would include escape shafts and the strengthening of foundations to existing bridges. He summed up by referring once more to the influence of Lucerne on the Antwerp Central building, by claiming that, 100 years on, the tradition of Swiss precision is being once more applied to railway infrastructure in Antwerp.

Related Files
Construction sequence
Illustration of the finished works
Alignment of the tunnels
Tunnel route