Abstract: The mandrel comprises a body having a longitudinal axis together with a radially-expandable annular assembly. The annular assembly presents a peripheral surface for pressing against a borehole and a peripheral surface for pressing against the body. Around the longitudinal axis, the annular assembly comprises a plurality of radial-expansion blocks. Each block has a first bearing surface, a second bearing surface, and two side surfaces disposed respectively facing a side surface of at least one adjacent block. The block are displaceable relative to one another between a radially-contracted configuration, and a radially-expanded, engagement configuration in which each side surface of a block is in contact with the side surface of the adjacent block.

Abstract: The mandrel comprises a body (16) presenting a longitudinal axis (X-X?) together with a radially-expandable annular assembly (18). The annular assembly (18) presents a peripheral surface (39) for pressing against a borehole and a peripheral surface (57) for pressing against the body (16). Around the longitudinal axis (X-X?), the annular assembly (18) comprises a plurality of radial-expansion blocks (40, 42). Each block (40, 42) presents a first bearing surface (44), a second bearing surface (46), and two side surfaces (48A, 48B) disposed respectively facing a side surface (48B, 48A) of at least one adjacent block (42, 40). The blocks (40, 42) are displaceable relative to one another between a radially-contracted configuration, and a radially-expanded, engagement configuration in which each side surface (48A, 48B) of a block (40, 42) is in contact with the side surface (48B, 48A) of the adjacent block (42, 40).