[322/03] Francke - Ingenia

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INFRASTRUCTURE Figure 2: The route of the Øresund Bridge ingenia The skill with which the contractors successfully planned and executed the construction of the tunnel, the bridge and the major dredging works can largely be ascribed to the Design-and- Construct concept which forms a part of all the major contracts. Optimum use of prefabrication also played a key role. As the Design-and-Construct concept lays down precise functional requirements for the whole project, contractors are responsible for the detailed design as well as for the construction work. Rigorous environmental requirements were in force throughout the construction period, governing both the construction of the link and the impact of the completed link on the surrounding environment. As the Danish and Swedish governments had stipulated that the link must not block the water flow through Øresund, careful trimming of the link’s design reduced the calculated blocking effect from 2.3 per cent of the water flow to 0.5 per cent prior to final adjustment. Compensation dredging in and around the alignment further reduced the blocking effect. Dredging and reclamation The dredging and reclamation contract included the initial construction works for the fixed link which began in August 1995. Over four years a total of 7.5 million cubic metres of (mainly) seabed material was dredged, two thirds in Danish waters and one third in Swedish waters. The seabed consists of gravel and stone, clay till and limestone with flint layers. Dredging was carried out by a number of dredgers, traditional bucket dredgers as well as a specialised cutter/suction dredger for the tunnel trench. The objective was for the completed link to have no net effect on the water flow and on the movement of salt and dissolved oxygen through Øresund to the Baltic Sea. Consequently the size and shape of the peninsula and the island were optimised to reduce the blocking of the water flow through Øresund. Further reduction to zero blocking was achieved by compensation dredging. All dredged seabed material was reused in the reclaimed areas which cut sediment spill to a minimum and, in addition, reduced the need for dumping sites as well as for import of sand and gravel. The dredging works included: ● Work harbours and access channels at the artificial island and the artificial peninsula 24
INFRASTRUCTURE ● A trench for the immersed tunnel ● Relocation of the Drogden Channel ● Relocation and deepening of the Flinte Channel ● Compensation dredging to achieve zero blocking of the water flow The reclamation works included: ● The artificial peninsula at Kastrup ● The artificial island which connects the tunnel and the bridge The 0.9 km 2 peninsula at Kastrup serves to bring together the passenger track from the underground station at Kastrup Airport with the freight track running north of the airport. The motorway along the northern edge of the peninsula joins the railway at the entrance to the tunnel portal. The peninsula also has a track leading to a railway maintenance area. The 1.3 km 2 artificial island south of the natural island of Saltholm forms the transition between the tunnel and the bridge. From the tunnel portal on the western end of the island, the motorway runs parallel to the railway to the eastern end, from where the railway runs under the motorway on to the two level bridge. The reclamation areas were constructed as basins surrounded by coarse pebble bunds lined with a geotextile membrane. The basins were then backfilled with clay to prevent the suspended sediment from escaping. Reclamation was carried out in stages as the bunds were completed, surrounding the individual sections. During filling at the artificial island, the traffic corridor for the high-speed railway was compacted to minimise any differential settlements which could interfere with the passage of highspeed trains. The reclaimed areas were completed with revetments, comprising layers of armour stones and filter stones. The revetments protect the tunnel against flooding during storms and high water. The immersed tunnel The tunnel extends approximately 4 km from the Danish coast at Copenhagen Airport to the artificial island in the middle of Øresund. The tunnel comprises five parallel tunnel tubes – two for the railway, two for the motorway plus a small tunnel as an escape gallery. The sheer size of the tunnel and the shallow waters in this part of Øresund made an immersed tunnel the natural choice. Figure 3: Aerial view of tunnel factory ingenia 25
Page 1: NILS FRANCKE ØRESUNDBRO KONSORTIET
Page 5 and 6: INFRASTRUCTURE Figure 5: Floating c

[322/03] Francke - Ingenia

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