One of the most significant and characteristic features of the city of Antwerp (Belgium) are its historical Scheldt quays. Stretching about 5.5 km along the western edge of the city centre, the quays were constructed at the end of the 19th century. At several locations severe indications of instabilities have been observed as early as during the construction of the quays itself. Despite the multitude of efforts to alleviate these instabilities over the last century, they continue until today.
In 2005, the council of the city of Antwerp and W&Z (i.e. Waterwegen & Zeekanaal, the independent agency of the Flemish Government in charge of the management of the Scheldt river banks) have agreed to carry out the most significant renovation works in over a century. Three main goals are at the centre of this long-term plan:
- The stabilisation of the historical 18 m high quay walls.
- The protection of the city against increasing storm surges as a result of climate change. This goal is part of the integrated Sigma Plan and requires a new 2.25 m high storm surge barrier to be built on top of the existing quay walls.
- The city government has seized the opportunity of these large-scale renovations to give the quays a facelift. The intention is to restore the city’s link with the river by incorporating urban development and mobility, by creating new public domains and by meanwhile preserving the historical monuments. The quay walls are a significant part of the latter.
In this paper, the focus is on the stabilisation of the historical quay walls. First, a brief overview of the history and the construction of the quays is given, along with a description of the stabilisation measures taken since their construction. Afterwards, this papers gives a description of two quay wall renovation projects that are being executed at the moment. Major design choices, innovative construction methods and lessons learned are discussed.
The first project is the renovation of the 700 m long quay wall situated at d’Herbouvillekaai and Ledeganckkaai. In 2008 there was still industrial activity ongoing on site. Stability calculations showed that the quay wall did not meet to the current stability standards and inspections showed that the wall was heavily damaged. Based on this determinations a load restriction was instituted and a monitoring campaign was started. Observations showed that the situation was getting worse so emergency measures were taken and industrial activity on the site was shut down. A quay wall renovation was necessary to allow for the construction of the new storm surge barrier and the establishment of the new public domain in a later phase. The existing gravity walls are entirely demolished and replaced by a tube combined retaining wall with 37.5 m long steel tubes. Two rows of anchors are attached to a second retaining wall located 38 m inland.
The renovation of the 900 m long quay wall situated at Cockerillkaai and De Gerlachekaai is the second project discussed in this paper. For this area of the quays a less invasive stabilisation technique is applied. A diaphragm wall with a depth of 30 m is installed behind the historical wall. The horizontal stability of the diaphragm wall is ensured with 2 rows of ground anchors every 1.8 m. An additional ground anchor is installed every 20 m at the location of a bollard. Between the original gravity wall and the diaphragm wall, stress relieving platforms are additionally installed to reduce the loads on the original gravity wall. Four drainage tubes per caisson are drilled through the original masonry walls to allow the stress relieving chambers to follow the tide in the river Scheldt.