South Stream Offshore Pipeline

Underground Crossing in the coastal zone

In April 2014, a key maritime and underground landfall connection was initiated along the coastline on behalf of Eni Saipem. ZÜBLIN was responsible for the microtunnelling works designed to safely guide South Stream Pipeline 1 from the landfall point into the offshore area.

At the heart of the project were four pipeline sections installed within four microtunnels extending to water depths of 23 metres. The works also encompassed the construction of four launch and reception shafts. With each pipeline measuring approximately 1,4 kilometres, the total pipe jacking length reached 5,6 kilometres.

Once the tunnel boring machine (TBM) had broken through the seabed, it was recovered in an exit pit within the Black Sea that had previously been dreged by Van Oord. Experienced divers attached the machine to a lifting spreader beam before it was raised to the surface by a floating barge.

The pipeline installation required equally careful planning. As the buoyancy force of the pipeline exceeded the weight of the jacking pipes, ten heavy steel pipes filled with steel sections and grouted with concrete were installed to provide the necessary counterweight. Afterwards, the pipeline was flooded and pulled through the tunnel to shore using an onshore linear winch. 

Scope of Work

• Four microtunnels from shore to 23 m depth 
• Construction of launch and reception shafts 
• 5,6 km of pipe jacking works 
• TBM recovery after seabed breakthrough 
• Installation of ten weighted steel pipes