Abstract

The increasing demand of power day by day in the country put power sector to Himalayas to harness the power potential. Utilization of underground space for infrastructure development is picking up momentum day by day. Every infrastructure project requires significant geological and geotechnical investigation for timely completion of projects. Lots of survey and Investigation is carried out to ascertain the geological and geotechnical feasibility of the hydro projects and for preparation of DPR. Construction of large caverns for power house presents challenges in terms of geotechnical engineering. Due to large size structure needs to ascertain behaviour of subsurface rock mass. The exploratory core drilling and exploratory drifts provide vital subsurface information. The subsurface exploratory drilling data provide immense help to understand subsurface information and reveals the subsurface behaviour of rock mass. The prior knowledge of weak feature can provide opportunity to prepare proactive solutions to mitigate these issues and structure design.

Authors are proposing simplified techniques to be implemented to understand ground realization and spatial reconciliation of weak zones/features with modern approaches in core logging with special core studies of Sunni Dam and Luhri Hydro Electric Projects Stage-II in Higher Himalayas of Himachal Pradesh.

Introduction

The in-situ samples are being collected through core drilling. The fundamental objective of core drilling is to collect subsurface samples in the shape of core besides sludge material. The depth wise linear information collected from a drill hole can be extrapolated through software’s available in the market to get planar geological information of the project/area. Geological examination of the cores and by logging we decides whether to carry out further investigations or search for other alternate sites. In most of the cases the core drilling is being carried out vertically, however presence of shear zones and its thickness sometimes warrants angular holes also in order to determine exact thickness which merely depend on the attitude of the discontinuities present in the area.

Sunni Dam HEP (382MW) is proposed on the river Sutlej and falls in District of Shimla and Mandi of Himachal Pradesh. The project is located in the inner Lesser Himalaya between Dhauladhar range in the south and Higher Himalaya in the north. The project envisages construction of a concrete gravity dam 83m high from deepest foundation level across river Satluj near Khaira village on State Highway-22. Co-ordinates of the dam axis are E 31°14’53", N 77°12’39". The underground power house and its appurtenant structuresare proposed on right bank.

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