Abstract: The invention relates to a method for drilling shafts (2) in ground layers (3). The method comprises of arranging a borehole casing (4) in the ground (3), lowering into the borehole casing (4) a hollow drill string (5) provided with a drill head (7) with cutting tools (8), arranging a water column (10) in the borehole casing (4), and then setting the drill string (5) into rotation (20) in the borehole casing (4) so that ground material (31) is dislodged by the cutting action of the cutting tools (8). At the position of the drill head (7) a first fluid (26) is injected under a first pressure into the ground layers (3) by means of one or more nozzles (25). The method has a higher drilling efficiency than the known method. The invention also relates to a device for performing the method, and a jack-up pontoon provided with the device.

Abstract: The invention relates to a method for erecting at sea a large slender body, such as the monopile of a wind turbine. The method comprises bringing the large slender body in a substantially horizontal floating condition at least partly underneath the work deck of a platform, attaching a tension cable to the slender body, and pulling on the tension cable using fixations means and guiding means that are provided at an edge of the work deck and are connected to it to gradually bring the slender body in an erected position along the edge of the work deck. The slender body is optionally driven into the under water bottom. The invention also relates to a device for performing the method. The method is reliable and obviates the use of large cranes.

Abstract: The invention relates to a method for erecting at sea a large slender body, such as the monopile of a wind turbine. The method comprises bringing the large slender body in a substantially horizontal floating condition at least partly underneath the work deck of a platform, attaching a tension cable to the slender body, and pulling on the tension cable using fixations means and guiding means that are provided at an edge of the work deck and are connected to it to gradually bring the slender body in an erected position along the edge of the work deck. The slender body is optionally driven into the under water bottom. The invention also relates to a device for performing the method. The method is reliable and obviates the use of large cranes.