AN OVERVIEW OF KONAR DAM ON NEED OF REHABILITATION

Transcription

1 AN OVERVIEW OF KONAR DAM ON NEED OF REHABILITATION Dipankar Chaudhuri, SE (Civil) A. K. Dubey, SE (Civil) and S. B. Pandey, DCE (Civil) DAMODAR VALLEY CORPORATION

2 OVER VIEW Problems Cracks Potential Conclusion

3 Upstream of Konar dam Down stream training wall of Konar dam Top of Konar dam Down stream channel below Konar dam

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6 MAJOR PROBLEMS Partial functioning of the existing hydro mechanical equipment Cracks in the dam body and in galleries Leakage through penstock Rip rap dislocation at upstream face

7 NATURE AND BEHAVIOUR OF THE CRACKS Cracks in the Inspection Gallery were reported first in Cracks are dominant in inspection gallery w.r.t operating and drainage galleries Mostly horizontal and continuous cracks At downstream face crack width and numbers are more Cracks are more profound at central blocks of the dam Depths of the cracks are of considerable amount Cracks were observed to be stabilized after 2009

8 Outer dam body at abutment Outer dam body at abutment Down stream face of inspection gallery Down stream face of inspection gallery

9 Down stream face of inspection gallery Down stream face of inspection gallery DSRP (2013) team in inspection gallery Leakage through penstock

10 Operating gallery Operating gallery Drainage gallery Drainage gallery

11 Plumb bob in drainage gallery Drainage hole in drainage gallery Crack in drainage gallery Drainage gallery

12 STUDY OF CRACKS AT DOWN STREAM FACE OF THE INSPECTION GALLERY V 7 V 9 V 16 V 20 Avg. Reservoir Level Max RL 430 Movement of dial gauge (mm) Min width Reservoir Level (m) Jan-84 Oct-84 Jul-85 Apr-86 Jan-87 Oct-87 Jul-88 Apr-89 Month

13 STUDY OF CRACKS AT DOWN STREAM FACE OF THE INSPECTION GALLERY Max width

14 Mr. Mueller (1976) Variation of the water load Temperature shrinkage during construction Dam acts partly as an arch dam Drying out action of normal air circulation C.M.D.D. OF CWC (1977) Tensile stress induced by temperature drop and shrinkage Stress due to seasonal variation would continue indefinitely Tensile stresses due to dead weight and water load Mr. Gruner (1979) Expanding action of upstream part of the dam or its foundation due to moist surface Shrinking action of downstream part of the dam or its foundation due to drying action Mr. P. M. Mane (1982) Structural problem EXPERT S OPINION BEHIND FORMATION OF THE CRACKS WRDTC, Roorkee (1984) High thermal gradient on account of heating of the downstream face of the dam in summer and induces higher tensile stress at d/s face of the gallery compared to the u/s face. Reverse trend is noted in winter when both faces of the gallery are in compression.

15 CAUSES OF CRACKS Probable cause of cracks was attributed to one or combination of different factors Temperature differential Alkali aggregate reaction in concrete Excessive uplift pressure in the foundation Settlement Construction faults/structural problems

16 MAJOR RECOMMENDATIONS Monitoring the movement of the cracks To measure deformation of the dam body Sonic experiment to assess depth of extended cracks To install temperature recording devices Providing self closing door shutter in the gallery to avoid steep temperature gradient To carryout photo elastic and detailed analytical studies To measure uplift pressure from the drainage holes To keep record of drainage discharge Grouting of the cracks by flexible epoxy compound To investigate obtaining core samples for confirming the construction interface Geophysical investigation of the dam body and to evaluate its quality of concrete Stability analysis of the dam on the basis of the evaluated strength of the concrete Underwater examination of the area in front of the inlet of the sluices (u/s) and the floor of the stilling basin

17 INITIATIVES BY DVC CWPRS, Pune, Government of India, investigated the cracks by Sonic tests ( ) and epoxy grouting was done Charting of the cracks of inspection gallery was done in January 1976 External temperature observations were started later on in 1983 Team of divers from Bhakra Beas Management Board examined under water upstream faces during Around 1985, core drilling was carried out to establish interface between the two stages of concrete Brass pins on the top of the dam were fixed (1984) to observe from a fixed point on the abutment to get an idea on relative deflection Dam was inspected by DSRP members in 2013 Project screening template was approved by the World Bank in December 2014 under DRIP Geophysical investigation is in process by CSMRS and will be completed within 2015

18 SEASONAL WATER AVAILABILITY IN KONAR RESERVOIR PERIOD ( ) Mean Inflow Median Inflow 75% Exceedance Inflow 90% Exceedance Inflow Evaporation Loss Inflow / Evaporation (MCM) Water Yr. 24 Monsoon Period Dry

19 MONTHLY WATER AVAILABILITY IN KONAR RESERVOIR PERIOD ( )

20 10 DAY WATER AVAILABILITY IN KONAR RESERVOIR PERIOD ( )

21 STORAGE STATUS ON GROUND OF SILTATION IN KONAR RESERVOIR Primary survey in 1955 Secondary survey in Storage in MCM Dead (up to EL m) Active (EL m) Flood (EL m) Gross

22 Crest gate Flood release Leakage through under sluice Rip rap and guard wall at d/s of right abutment

23 Discharge in Cumec

24 RESERVOIR ROUTING USING MODIFIED PULS METHOD Case 1: Available freeboard 1.53 m Case 2: Available freeboard 1.66 m Minimum permissible freeboard: 1.5 m [ IS 10635:1993(reaffirmed 1998)]

25 CONCLUSION In existing scenario, storage ratio of this reservoir in respect of its water availability is very high as Further, it is observed that revised PMF will also be absorbed safely in the existing flood cushion with slight encroachment in the free board. Actual reasons behind formation of cracks could not be ascertained till date. However, after obtaining CSMRS and other investigation reports, DVC will be in a position to take measures for repairing of the said cracks as well as to rectify other problems through DRIP. Thus, dam will get a prolonged life and definitely, Nation will be benefitted.

26 THANKS