Repairs to the carriageway and all engineering structures will ensure the availability and safety of the national highway for another 15 years.
Project description
The section of the N04 was built between 1976 and 1981 and was in need of rehabilitation. The maintenance project included repair work on the carriageway and on all engineering structures such as bridges, underpasses and retaining walls.
As part of the maintenance measures, the N04 between the Schwyz junction and the north portal of the Mositunnel was upgraded to such an extent that only minimal maintenance measures will be necessary until the complete renewal of the route. The availability and safety of the national road was thus guaranteed for another 15 years.
The following work was carried out in the various construction phases:
In Phase 0 (preliminary work, July - December 2019), the temporary access roads and installation sites were constructed. Scaffolding was erected at the bridge soffits and repair work started. At the same time, the bridge bearings were replaced.
In Phase 1 (Altdorf lane, January - March 2020), anchor work started on the uphill retaining walls. In the road area, various cable conduit blocks and foundations for signal gantries were newly constructed. At the retaining walls Urmi 02 and Zingel, the existing bracket heads were demolished and provided with a new guide wall. The Sechzehni bridge was repaired on one side.
In phase 2 (Altdorf lane, March - July 2020), repair, waterproofing and mastic asphalt work followed on all viaducts. On the uphill retaining walls, the concrete longarines to the anchors were constructed. On the Zingelbrücke exit ramp, the bracket heads were rebuilt under traffic.
Furthermore, in this phase the deck pavements were replaced in stages and provided with temporary markings. The noise barrier "Mitte" was replaced.
In the last phase 3 (Zurich lane, July - November 2020), the Schwyz exit was completely closed for 5 weeks. During this time, the decks on both the Zingel and Urmiberg bridges were demolished, various repair works were carried out and the waterproofing was renewed. On the Zingel bridge, 250 m of bracket head were also demolished and rebuilt. At the end of the total closure, the surface courses from the Urmiberg bridge to the Schwyz junction were renewed.
In addition to the work in the area of the Schwyz exit, repair, sealing and mastic asphalt work was carried out on the Sechzehni and Muota bridges and the Brunnen cantonal road underpass. In night work, the surface courses were renewed in the Mositunnel and Brunnen exit areas. Finally, the surface courses in the route were renewed and the final marking was applied.
Special features
The major challenge of the project was the very short construction time for the rehabilitation of the total 1.35 km long viaducts and overpasses. Therefore, the construction sequence was optimized down to the last detail.
A special highlight was the five-week intensive construction phase in July and August 2020, when approx. 6,500 m2 of bridge superstructure including the Schwyz exit ramp were renewed during the summer vacations.
