Assessments of Jiroft Concrete Arc Dam foundation Displacements by Use of Extensometers Data

Safe operation of dam has been based on three factors of structural integrity of dam, monitoring of dam and emergency preparedness. Instrumentation and data acquisition by instruments installed in different parts of the structure is one of the methods of monitoring. Jiroft Dam is an arch dam, that its extensometers data set has been used in order to understand the behavior of dam foundation during 20 years period of operation. The dam is 40km north-east of the city of Jirof, has been constructed on the Oligomiocene limestone. Jiroft Dam’s extensometers are from multi-rode type and have a maximum depth of 40m. The extensometers have been installed in the both side of upstream and downstream. Foundation displacements are affected from the reservoir loading and its water level. Foundation uplift in upstream and foundation subsidence in downstream are proportional to the reservoir water level variation. Moving average function used in order to eliminate short-term effects of annual changes in the water level. The highest values of uplift in upstream and subsidence in downstream occurred in the middle block and are about 8 and 3 mm, respectively. Downstream side of some blocks show a subsidence with constant small rate of about 0.1 mm/year. It is necessary to regularly dam monitoring considering continues constant rate of subsidence in mentioned blocks.