Abstract: The present invention relates to a drilling tool and method for modifying a blind hole in a blade root insert of a wind turbine. The invention further relates to an apparatus and method for cleaning a blind hole. The method for modifying a blind hole comprises: removing a blade screw located in the blind hole, inserting a drilling tool into the blind hole, fixing the drilling tool in a drill, recessing the blind hole by a predetermined depth, with a maximum diameter of the end section and of the hole bottom after recessing being smaller than or equal to a diameter of the end section prior to recessing and a transition from the end section to the hole bottom being round after recessing, removing the drilling tool and the drill, mounting the blade screw in the modified blind hole.

Abstract: The present invention relates to a securing device (100) for additionally securing a foundation (1) having a foundation mounting part (6) that is incorporated in a concrete structure (2) for holding a construction (14), in particular a tower of a wind turbine, wherein the securing device (100) includes at least one securing structure (102, 104, 106) with a mounting section (108, 110, 112) and a support section (114, 116, 118). According to the invention, the mounting section (108, 110, 112) for mounting the securing structure (102, 104, 106) is provided on the foundation mounting part (6) and the support section (114, 116, 118) for introducing foundation forces is provided in a section (23) of the concrete structure (2) that is distant of the foundation mounting part (6). The invention further relates to a foundation and method.