PURPOSE: To enhance the maintainability of safety in a waste disposal facility, when forming a water cut-off structure by the junction of a polyethylene excellent in impact resistance and vulcanized rubber having a small coefficient of thermal expansion, by facilitating the work of laying water cut-off sheets, and enhancing water blocking properties.

CONSTITUTION: In a water cut-off structure in which water cut-off sheets are laid over the foundation of a waste disposal facility 1 which consists of a roughly flat bottom surface 2 and a face of slope 4, the water cut-off sheet 3 made from a polyethylene is placed on the bottom surface 2, while the water cut-off sheet 5 made from vulcanized rubber is place on the face of slope 4, the junction 6 of the water cut-off sheets 3, 5 being located within a range from the boundary between the bottom surface 2 and the face of slope 4 to half the height of the face of slope 4. A joint made from a thermoplastic elastomer is placed at the junction 6 of the water cut-off sheets 3, 5, the polyethylene water cut-off sheet 3 and the joint are bonded together by thermal fusion, and the vulcanized rubber water cut-off sheet 5 and the joint are joined together with a curing tape between them.