... orogenic phase, with a NW-SE trend at the western parts and NE-SW at the eastern parts. Alborz Mountains is limited to the Central Iran to the south, and its northern area is marked by some large faults. The Siah Bisheh powerhouse cavern (hereafter named PHC) with 132 m length, 25 m width and 46.5 m height...

...*114m (span, height, length) plus extension two headrace tunnels/pressure shafts for each stage with 10.5m excavation diameter two tailrace tunnels for each stage with 12.5m excavation diameter main access tunnel and a separate access tunnel to the PHC-Extension both with 8m excavation diameter...

... distinguished layers dipping at approximately 25° to the east. The upper layer intersects the roof of the PHC and intersects the transformer hall walls. The lower layer intersects the draft tube level at 190 to 205 m. The intermediate mudstone layer intersects the upstream and downstream walls of the PHC...