Successful excavation of Surge Shaft in weak rock mass: A case study of 240MW URI-II HE Project, NHPC, J&K

DOI

10.2991/rare-16.2016.29How to use a DOI?

Keywords

Surge shaft; HRT; THPS; Murree Formation; Bedrock; RMR; NATM; Rock Bolt; Contour Blast; Pre-grouting; Line Drilling; Air-deck blasting; Pull out test; Shotcrete; wiremesh; chain link fabric; ribs

Abstract

Surge shaft serves to absorb the hammering effect of water from pressure tunnel generated due to the sudden stoppage of turbines, by accommodating surges/mass oscillations during load rejection/acceptance until the conduit velocity attains a steady state in water conductor system of a hydel Project. The location of surge shaft is constrained by alignment of pressure tunnel (HRT) and power house. In the past at various places there were incidences of failures during the excavation/ construction as well as post-operative problems due to charging of hill slopes. This paper is an attempt to bring out site specific measures vis-a-vis geological conditions encountered in construction of a 26.6m dia (excavated), 78m deep (EL1275 to 1197m) surge shaft for accommodating surge water of 4.235 Km long, 8.4m dia HRT. This surge shaft was constructed in weak to medium strong intricately folded, fractured sequence of Murree formation (RMR 25-50). The shaft excavation included an open excavation of slope overlooking the shaft and shaft sinking with full face up to El 1275M to 1266.5M, a pilot shaft from El 1266.5M to El 1197M and side slashing. Pre-grouting, peripheral control blasting and variations in blasting pattern such as contour blasting, Air-deck blasting and line drilling, followed by systematic rock support, and were practiced at Uri-II Surge shaft for its successful completion

Copyright

© 2016, the Authors. Published by Atlantis Press.

Open Access

This is an open access article distributed under the CC BY-NC license (http://creativecommons.org/licenses/by-nc/4.0/).

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TY  - CONF
AU  - Kumar BNS Naveen
AU  - Sahoo Radhendra Narayan
PY  - 2016/11
DA  - 2016/11
TI  - Successful excavation of Surge Shaft in weak rock mass: A case study of 240MW URI-II HE Project, NHPC, J&K
BT  - Proceedings of the conference on Recent Advances in Rock Engineering (RARE 2016)
PB  - Atlantis Press
SP  - 180
EP  - 185
SN  - 2352-5401
UR  - https://doi.org/10.2991/rare-16.2016.29
DO  - 10.2991/rare-16.2016.29
ID  - BNSNaveen2016/11
ER  -