Installation of Shore Approaches and Sea-Lines Using Trenchless Methods: Technologies and Case Studies

Abstract

From the mainland into the sea or vice versa, for a sea outfall, an intake or landfall, a pipeline is laid from the mainland out to sea or into a lake or river. Such lines can be installed by Trenchless Technology using pipe jacking, segment lining or pipeline installation methods (HDD and Direct Pipe), according to the requested diameter, length and geological conditions. This paper shows different trenchless installation methods, including those for large diameter pipelines. Selected case histories show the multipurpose use of the trenchless outfall technology in various industrial sectors. Herrenknecht machines have installed in numerous marine outfall systems safely beneath the seabed, such as sewer and brine outlets or landfall constructions for oil and gas pipelines. Another application field which has been gaining importance in recent years are water intake and brine tunnels for desalination plants. With machine concepts for Offshore Foundations, e.g. wind-parks for renewable energy, Herrenknecht has also entered the energy sector. Tunnels and casings for offshore-onshore connection lines and cooling water intakes for coastal power plants complete its trenchless range of energy solutions.

This paper highlights the environmental and economic aspects of tunnelled outfall construction. Trenchless installation methods have less impact on the environment and on the existing infrastructure than methods applying open-cut trenching. They reduce environmental impact and can also be carried out in heavily built-up areas. Shipping and tourism remain unaffected. The pipeline is better protected against damage and therefore has a longer lifetime. Due to the fact that the tunneled pipeline is laid underground, it is safe and maintenance-free for decades.