(Proceedings of Conference on Large Dams and Hydropower Development, 26–28 May 2004, New Delhi, pp.V/14–24).
The paper presents the construction methodology of handling cavities treatment of head race tunnel during excavation of heading. The case is discussed in details for adit I and adit V, where rocks were found very weak and cavities formed at HRT junction of adit I and adit V at RD 170 m to 176 m. In adit V, cover was found 80 m to 230 m before Elaichi Khola. At this location it took 5 months and 12 days to pass ahead. For balance portion of HRT in rock class “V”, the average progress achieved was 1 m for day with all treatment like Rib ISMB 250 x 125 mm @ 1 m c/c with tie rod, forepoling in alternate cycle and backfill concrete of grade M15 A40. The maximum progress achieved was 52 m in a month with all treatments in rock class V. During excavation seepage was found moderately.
Construction methodology, Cavities treatment, Forepoling, Seepage
