Site Specific Seismic Study and Dynamic Analysis done by IIT, Roorkee

The Government of Kerala entrusted Dr. D.K. Paul of the Earthquake Engineering Department of IIT, Roorkee to carry out site specific seismic study for Mullaperiyar dam. The study conducted by IIT, Roorkee has concluded that the Maximum Considered Earthquake (MCE) possible in Mullaperiyar region is of magnitude 6.5 in Richter scale and it produces a PGA of 0.21g at the site.

CWC has taken an assumed value of 0.1g and the Expert Committee a value of 0.12g as the seismic parameter of the Mullaperiyar Dam. In the light of the site specific study by the IIT, Roorkee that the seismic parameter applicable to Mullaperiyar dam is 0.21g, the conclusion of CWC and the Expert Committee that Mullaperiyar dam is seismically safe on the basis of assumed lower parameters as above is not at all dependable and is thoroughly misleading.

The Detailed Structural Stability Analysis of IIT Roorkee clearly indicate the following:

• The Main Mullaperiyar Dam even under DBE condition (seismic co-efficient of 0.12g) under reservoir level of 136ft, the value of tensile stresses are found more than double the ultimate apparent seismic tensile stresses. The MCE condition makes the things much worse.
• Even without earthquake forces, the Main Mullaperiyar Dam is unsafe for flood conditions (MWL) since the tensile stresses in the heel of the dam are found to be more than double the permissible apparent tensile stresses.
• In the normal operating conditions, the tensile stresses in the Mullaperiyar Dam at the heel are at the border level of the allowable stresses.

IIT, Roorkee made the following recommendation finally, "Based on the analysis, both Main Mullaperiyar Dam and Baby Dam are likely to undergo damage which may lead to failure under static plus earthquake condition and therefore needs serious attention."

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