TEMPERATURE STUDIES FOR GRAVITY DAMS

Abstract

The necessity for instrumentation in dams to assess their structural behaviour ' and rationalise future designs need hardly be emphasized. With the increasing construction activity in India the instrumentation -. a neglected art upto recent past assumed importance. Amongst the gravity dams the material that has been frequently used fcr construction is stone masonry. Many types of instruments have been developed in foreign countries and a study for the correct choice of the type of instruments for Indian conditions will lead to useful and economic installant tions. In this dissertation a critical review of the various aspects of instrumentation in concrete dams (with special reference to masonry dams ) has been presented. The basic instrumentation in concrete dams is for deflection and settlement measurements; strain and stress measurements, temperature measurements and uplift & seepage measurements. The "state-of»the.art" in each of the above items is reviewed. The different types of instruments are classified based on the working principle and location of installation. The characteristics of the two main types of instruments viz., resistance wire type and vibrating wire type are compared, v A study of the behaviour assessment, at some of the typical dams has been included to have a critical apparaisal of various techniques, giving emphasis to masonry dams. After a brief review of the instrument installation procedures and relevant aspects, the various types of measurements and techniques adopted for them is critically assessed. Further research,to establish the reliability of the performance of the various instruments available, under different trade names, appears to be necessary to enable one to choose a particular instrument for a particular situation with confidence. The necessity for special types of instruments for masonry, like long.-ra.nge strain gauges and invar tapes for measuring strain, is pointed out. The need for establishing properties of masonry like creep, autogenoous growth and co-efficient of expansion is emphasized to enable one to predict stress pattern in the dam. purpose oriented limited instrumentation for medium dams and over-all behaviour instrumentation to rationalise the theory and to improve knowledge of design criteria for major dams is recommended. It is concluded that better installation systems are possible with systematic planning and separate organisation to install, observe, analyse and interpret data.