Patent ID: 10487468

Abstract:
A method and a mandrel for forming a cavity at a target location. The mandrel may include a main drilling shaft, a plurality of T-shaped elements, a hollow-cylindrical-shaped element, and a plurality of parallelepiped-shaped stiffener plates. The main drilling shaft may include a hammer insertion part positioned at a first end of the main drilling shaft, a bore head positioned at a second end of the main drilling shaft, and a medium part positioned between the hammer insertion part and the bore head. The plurality of T-shaped elements may be mounted adjacently around the medium part in a way such that forming a closed octagonal from a top-view of the mandrel. A first size of a first cross-section at a first location from a top-view of the plurality of T-shaped elements around the medium part may be larger than a second size of a second cross-section at a second location from the top-view.