Crack detection, analysis and rehabilitation of an old masonry dam

A 60 year old, 82 m high, masonry dam suddenly developed heavy leakage in the form of a water-jet through the ground, on the downstream. On the presumption that this leakage was through the masonry/rock contact, a grout curtain from dam top was proposed. Diligent observations during drilling of the first few grout holes, revealed total loss of drill flushing water and sudden drop of drill rods at about mid-height of the dam. A serious analysis was quickly carried out by the field engineer, which lead to the possibility of diagonal cracking of the masonry dam. Likely causes were evaluated and a plan prepared for rehabilitation of this important dam. First phase of the work was completed in 4 months available before the monsoon and involved drainage holes, cable anchors, shear bars and body grouting.