WATERPROOF SHEET

PURPOSE:To prevent damage to the connection section of a waterproof sheet caused by spring pressure by connecting a water - impermeable sheet closely to a water permeable sheet so that both ends are in a free state, and connecting a water impermeable reinforced sheets closely to both ends. CONSTITUTION:When a water permeable sheet 3 is laminated on the whole surface of a non-water permeable sheet 2, both ends of both sheets 2 and 3 are not secured and are connected closely to each other in a free state. After that, a water impermeable reinforced sheets 5a and 5b are fully connected closely to both side ends 4a and 4b of the water permeable sheet 3. Both free ends 6a and 6b of the water permeable sheet 2 are so formed that they are longer than both ends of the water permeable sheet 3. Then, for the connection of a waterproof sheet 1, the water- impermeable sheets 5a and 5b are overlapped and are fixed to a primary lining concrete 7 through a fixed member 10, and a principal rafter of the water- impermeable sheets 6a and 6b is made to thermally connect to each other. According to the constitution, spring pressure to a connection section 11 can be significantly reduced.