HPP Parbati (India) Inclined Shafts: TBM Concept, Segmental Lining and Site Experience

Stage II of the 2,000 MW HPP Parbati in Himachal Pradesh, a northern district of India at the lesser Himalayan zone, will generate a total power of 800 MW. A Joint Venture of Jäger Bau GmbH (Austria) and Seli SpA (Italy) completed together with Gammon India Ltd. in December 2006 the first inclined shafts in India driven by a double shield tunnel boring machine. The two parallel 30° inclined underground pressure shafts of 1,500 m in length each have been lined by precast concrete segments simultaneously to the TBM heading. Especially the second shaft could be completed in a record of 109 working days respectively with an average daily production of almost 14 m/d! A steel lining with an inner diameter of 3.5 m is underway to be installed in the two shafts. That project might have set a milestone for the execution of inclined shafts – for sure in India but may be even in other countries as well. The paper describes the mechanical excavation of these two shafts under severe conditions in a remote area.