Strategy for Rehabilitation and Strengthening of Dam - A Case Study of Temghar Dam

Abstract

Construction of Temghar Dam took place in stages from 1997 to 2010 due to the number of difficulties including forest clearance and allied issues. Construction work was completely stopped in July 2002 after creating a storage capacity of around 63%, which was regained back in the year 2009 almost after seven years and completed in the year 2010. Leakage was observed first time during its construction stage itself in the year 2001 which was observed increasing day by day as the reservoir water level increases. In the year 2016-17 a considerable leakage of around 2587 lps was noticed, so to deal with the leakage problem and to ensure the safety of dam it was proposed to provide the remedial repair measures in two stages i.e. long term and short term. Short term remedies includes, U/s drilling & grouting from top to inspection gallery and Inspection gallery to foundation gallery, drilling & grouting on D/s surface, cleaning vertical porous drains, curtain grouting in remaining portion in foundation gallery, monolith joint treatment, and U/S treatment – shotcrete with mesh and anchor bars into the masonry. Long term remedies include concrete backing cement grout consisting of fly ash, silica flume and admixtures such as SPG 1A, ACC2025 and ADMGP1 is used for grouting after studying and testing other grout options. Apart from laboratory tests, Marsh Cone Test, settlement test, pH, compressive strength and density test were carried out at the site. Various type of machinery such as Drilling machine Water intake test machine with single drum, grouting machine with double drum mixer & with RPM 1500 to 2000, Grout pump, water meter, pressure meter and batching plant with SCADA system are used in grouting process. Leakages before and after grouting were observed in terms of Lagoon values. Observations are recorded at different R.L.s and at different chainages to get an exact picture of leakages. It was observed that almost 80% leakage was stopped by June 2018. With the help of correct implementation of grouting techniques, leakages through masonry dam can be controlled however grouting or any other remedial measure is not an alternative to poor workmanship and quality control.