The need for sustainable solutions in the energy sector has led to the rapid increase of offshore windfarms around the globe. The areas with ideal soil conditions are gradually being occupied, pushing the offshore wind industry to search for methods of installing wind turbines in hard terrain. So far, the installation of monopiles in weak rock, if successful, required the use of additional casings and grouting. In this thesis project, an alternative installation method is investigated, in which the monopile itself is used as casing, avoiding the waste of extra material.

The ‘drill-drive’ installation method under investigation consists of an initial drill-out of the rock from the inside of the pile and its subsequent driving into the seabed with a hydraulic hammer. No casing is used and a cutting toe is equipped in the bottom circumference of the pile, being responsible for breaking through the rock.

Through finite element analysis, the structural integrity of both the monopile and the cutting toe during the drill-drive process is assessed. A driveability analysis is conducted for a seabed of different types of rock and the first conclusions on the feasibility of this novel installation method are drawn.