US Patent 7955026 Method for rehabilitating a manhole

To line an inner circumferential surface of side walls of a manhole, a rehabilitating sheet made of a sheet material resistant to water and corrosion is provided in the form of a bag having a shape corresponding to the inner circumferential surface to be lined. The rehabilitating sheet is inserted into the manhole to be lined. Block and plate frames are coupled inside the bag of the rehabilitating sheet to support it so as to have the shape corresponding to the inner circumferential surface to be lined. A gap between the rehabilitating sheet and the inner circumferential surface of the side walls of the manhole is filled with a filler, which is then hardened to line the side walls of the manhole. Pairs of plate frames having different diameters are coupled to each other to provide ring plates having different diameters. The ring plates are stacked one by one from the maximum one to support the rehabilitating sheet so as to have a shape of the inner circumferential surface of the inclined side wall portion of the manhole.