Report of retrofit construction using 'Multiple Nuts Bar' for underground RC structures at electric power stations

A retrofit method names 'Multiple Nuts Bar' is developed for the underground RC structure. This method can retrofit the outer wall of the existing box culverts from their insides without excavation. Application examples of this method at an electric power company are reported here. A thermal power plant's sluice gate, and a nuclear power station's duct and sluice gate were retrofitted. In the case of other nuclear power stations, underground RC structures will comprise thick walls of thickness 2.0–2.5 m. Grouting test was conducted using the long 'Multiple Nuts Bar' for confirming the mortar filling performance against thick walls. Finally, it is revealed that entrapped air does not exist around the 'Multiple Nuts Bar'. (author)