The scanning of upstream side of the Mullaperiyar dam using a remote operated vehicle by the Central Soil and Materials Research Station on directions from the Empowered Committee of the Supreme Court had found serious damage to the masonry structure between 95 to 106 feet from the base of the dam, retired engineer M. Sasidharan who was observer of Kerala during the scanning said in a report to the government.
Apart from innumerable pot holes, crevices and other openings that were visible on the surface of the dam, the masonry cover provided at the upstream side of the dam was seen to have undergone a crushing between 106 feet and 95 feet throughout the entire length of the dam.
“The damage that the dam has undergone in between the above noted elevations is so severe that no amount of rectification can salvage the dam from a disaster. Even a medium nature of earth quake of four to five magnitudes (on the Richter scale) near the dam site can shake the already loosened masonry cover to a collapsible condition.”
The scan results projected deterioration at all 34 sections of the dam from massive erosion of lime surki mortar from the rubble joints; exposing huge voids, deep pot holes, wide open joints, deep crevices and hollowness on the upstream periphery of the dam. “On most of the sections at this area, rubble was seen in a loosened condition, suggesting that the dam has undergone an irreparable damage.” Mr. Sasidharan said that some of the damage was caused by mistakes in the strengthening works carried out by Tamil Nadu following recommendation of the Central Water Commission in 1979.
The dam had undergone a crushing on account of the additional load of nearly 21.75 tons per feet applied on the top of the dam in the form of RCC capping as part of emergency strengthening measure. The pre-stressing done by cable anchoring through the upstream masonry portion might have loosened and damaged the masonry. Mr. Sasidharan told The Hindu that when the original case over raising of water level was argued before the Supreme Court, Kerala had failed to present the argument that the dam was structurally weak.
What it had presented was applicable to many other dams. In court records, the Mullaperiyar dam was stated as a masonry dam whereas it was a composite dam. The inner core (62 per cent) of the dam was constructed with hydraulic lime surki mix and its upstream and downstream sides with rubble masonry.
He said that no present day engineer would dare even in his dream to design and construct a dam using hydraulic lime surki mix, in the manner of Mullperiyar dam, as this hydraulic lime surki mix is a very weak and unsound material, especially to withstand earthquake forces and high water pressure when compared to dams constructed with rubble or concrete materials.
This was the reason why no country in the world venture to construct a dam using hydraulic lime surki mixes, even though the material is available in plenty.