MONITORING THE BEHAVIOUR OF A CONCRETE GRAVITY DAM

Abstract

The catastrophic consequences of the failure of a dam, make it imperative that safety of the dams should be ensured at all costs. 'In order to monitor the behaviour of dams, a large number of instruments are usually provided, which include stress meters, strain meters, plumb-lines, uplift pressure pipes, resistance thermometers and joint meters. These instruments are used for the measurement of stresses, strains, deflections, uplift pressures, temperature changes and joint movements at typical locations of the dam. In order to check the reliability of the instruments and to interpret the measured data, an analytical assessment of the dam behaviour is necessary. The theoretical analysis of the dam can be carried out by various methods such as beam analysis and finite element analysis. However, for an accurate determination of the stresses and deformations, a finite element analysis is necessary. In this dissertation, a review of the factors influencing the dam behaviour is presented. Instruments used to monitor the structural behaviour of dams, have also been briefly discussed. A few case histories of the structural behaviour of some important dams has been included. The analysis of two instrumented blocks of a 143 m high concrete gravity dam has been carried out. Field data as actually measured has been utilized. For the purpose of comparison of results obtained analytically with those obtained from instrumental measurements, those loads have been considered to which dam is subjected after the installation of the instruments. The actual (iii) sequence of installation of plumb-lines in the various blocks have been taken into account. It is found that temperature does not play a very significant role in the overall behaviour of the dam. A comparison of the measured data has been made with those obtained analytically and a good comparison has been obtained for a particular block of the dam. Thus some of the instrumental measurements can be reliably used for assessing the performance of the dam in future. (