Method of making a covering for a containment pool, tank or enclosure

A method for making a covering for a containment pool, tank or enclosure comprising an assembly of a series of adjacent sheets, the adjacent sheets being welded to one another to form a part of a surface of the covering by making a weld bead, the method comprising:

• placing the adjacent sheets side by side and parallel to a first wall at a predetermined distance from the first wall, each sheet comprising anchoring elements fixed to a first face of the sheet arranged facing the first wall, in order to fix each sheet to the first wall, and
• placing a rail situated between the anchoring elements of two adjacent sheets between the first wall and the first faces of the adjacent sheets, the rail facing an area to be welded between the two adjacent sheets, and comprising side walls and a back base designed to receive a movable mechanical assembly,
• wherein welding of the adjacent sheets is performed after the rail has been fitted,
• the method further comprising:
• inserting the mechanical assembly in the rail, said mechanical assembly comprising a neutral gas diffusion volume coming into contact with the first faces of two adjacent sheets due to an action of a support element pressing between the rail and the mechanical assembly,
• making the weld bead between two adjacent sheets in the neutral gas diffusion volume, and
• removing the mechanical assembly,
• wherein welding of the adjacent sheets is a full-penetration butt welding and is followed by pouring concrete between said first wall and the sheets, the anchoring elements of the sheets being completely independent from the weld bead after the concrete has been poured.