Brief description
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The research work encompasses Engineering Geological Evaluation of the suitability of the dam foundation, suitability of the Powerhouse site and the assessment of stability of the hill slopes around the Kishau Dam reservoir. On the basis of surface and subsurface investigations carried out at the dam site, an evaluation of the dam foundation condition has been done. The foundation evaluation studies include 3D logging of drifts, interpretation of drill hole data and water pressure tests. The stability analysis of abutments has been carried out by modifying the analytic technique of Hoek & Bray, where the effects of inclined upper slope surface and tension crack has been incorporated.  In order to improve the overall foundation condition, suitable remedial measures have been suggested. The Kishau dam site envisages the construction of a surface power house. For housing the power units, a terrace has to be created by excavating the adjoining hill slopes. The stability analysis of the hill slopes adjoining the powerhouse has been carried out and based on the result a cut slope design has been suggested. The reservoir area has been mapped on 1:15,000 scale. For the stability analysis of the hill slopes in the reservoir area the data pertaining to structural discontinuities has been collected from 100 localities.  In the entire reservoir area 70 potentially unstable slopes have been identified for the detailed stability analysis.  A Computer Program ROSS has been developed to identify the possible mode of failures. The detailed analysis  has been carried out for both natural and water impoundment conditions. An attempt has also been made to, study the possible impacts of these unstable slopes on the stability of dam in the event of failure.

The foundation of the Kishau dam has some minor engineering geological problems, but it can be rendered stable and competent to withstand the loads to be imposed by the dam, after adequate foundation treatment. The proposed powerhouse site is not found to be suitable because of some engineering geological problems. Therefore, an alternative site has been suggested. However, safe cut slope design has been suggested for both the sites. The stability studies of reservoir slopes show that most of the slopes are stable, except for a few slopes, which are critical. Though, the reservoir impoundment may stabilise some of the critical slopes, few of them will be unstable. But in case of failure, they are not likely to effect the safety of the dam. In view of the above it can safely be concluded that Kishau dam project appear to be technically sound with minimum engineering geological problems.