A geo-technical overview of impediments in achieving consistent and optimum advancement rate in hrt at parbati hydroelectric project stage-II

The tunneling in 31.5 km long HRT of Parbati hydroelectric project, stage II, is advancing through the lesser Himalayan zone in Kullu district of Himachal Pradesh. The 6m finished dia HR is to conduct water from river Parbati from Pulga (dam site) to Suind (power house site) via Sheelagarh Valley. Through 5 intermediate Adits and 11 faces, the excavation is under progress using the conventional drill and blast method except for the 9.05 km long face IV, which is being bored by TBM. Along the proposed alignment the tunnel envisages to negotiate through rock masses comprising of different litho types belonging to different geological formations. In addition to other tectonic imprints of Himalayan orogeny, the alignment also is laid across the Jutogh thrust which separates the Jutogh and Banjar formations. The rock bursting kind of phenomena at face-III and the hindrances to advancement with, TBM due to frequent wedge releases at cuter head area have significantly reduced required rate of advancement. The subject of this paper is to show the modifications in support systems and machinery required to be done to improve the advancement rates light of the ground behavior patterns specific to rock masses dominated with Manikaran quartzite and Bandal granites.