Long-term dam safety monitoring of Punt dal Gall arch dam in Switzerland

Abstract

The 130 m high Punt dal Gall dam is located at the Swiss-Italian border in the South-eastern part of Switzerland and was completed in 1969. The dam is founded on highly folded and partially crushed dolomite and limestone formations. A grout curtain with an area of 120,000 m2 was provided for controlling seepage. For the monitoring of the dam deformations five inverted pendulums were installed in the dam and three in the rock foundation of the right abutment outside of the dam. For a seasonal water level fluctuation in the reservoir of about 60 m the maximum amplitude of the radial displacement is 25 mm, which includes both the effects of the water load and temperature effects. Furthermore a comprehensive geodetic network was established, 57 joint meters were installed and cracks in the crest gallery are monitored by crack meters. There are also thermometers, piezometers and rocmeters. Springs at the left and right banks of the dam are monitored and chemical analyses of the seepage water and springs are performed regularly. The dam is equipped with strong motion instruments and several near-field earthquakes have been recorded in the past. The paper describes the long-term safety monitoring of this 42 years old arch dam. A short description of the Swiss practice in dam safety monitoring and emergency planning is also given.