Evaluating the use of mineral pumice in falling zones of internal pressure tunnels (Case study: Water transfer tunnel of Sardasht dam power plant)

Internal pressure tunnels and wells that are mainly used to transfer water from dam reservoirs to electrical power plants in rivers downstream are considered among the power plant’s permanent facilities. In order to design reinforced concrete structures in these tunnels, recognizing the concrete lining behavior and interaction between rock mass and concrete and also the effect of internal pressure on the concrete shell and rock mass is of great significance. One of the important and effective issues in inner lining forces is their filler type. In this paper, using the finite difference method by the FLAC software, the analysis of Sardasht dam water tunnel which has been filled with mineral pumice in falling zones has been carried out. Results indicate that by increasing the falling zone thickness while the lining is porous or non-porous, the inner forces are decreased.