INSTRUMENTATION OF DAMS AND POWER HOUSES WITH PARTICULAR REFERENCE TO IDUKKI PROJECT

Abstract

Analysis of the behaviour of • massive structures is an extremely complex problem an account of various uncer.. tainties in the material properties and loading on the structure. A sophisticated measurement programme is required for determination of the structural behaviour. The measurement of the structural quantities is of vital importance to the engineer, since this enables him to construct the stress pattern in the structure due to all external forces. This knowledge can very profitably be used for future designs and performance analysis more accurately. Measurement of quantities other than stress and strain is also important in the sense they help to detect the behaviour in zones where stress or strain meters are not provided With the construction and design of, a large number of massive structures involving investment of crores of, Rupees 'the instrumentation of, structures' .. a neglected art until recently assumes importance. This study presents a critical review of the various aspects of instrumentation in dams and power houses with special reference to the Idukki project.*, The various quantities to be measured in a structure are temperature, stress, strain, joint movement, volume change i cracks, deflections etc. The basic instruments used are thermometers, stressmeters, strainmeters, joint. meters, no stress strain meters, crack detectors, pendulum, geodetic targests, clinometers, etc.. The instruments used are classified into various categories such as instruments For dams, instruments for power houses, earthquake measuring instruments etc. with emphasis given to dam instrumentation. Characteristics of two types of instruments viz vibrating wire and resistance wire types for installing in structures are dealt with in detail.' In the Idukki dam, a number of, instruments are ins_ tailed with the following objectives and for long term measurements, (i) To check the actual performance of the structure and to compare the values of stresses, deflections etc•,with those made in the design analysis. (ii) To detect the development of abnormal conditions in the body of, the dam and its foundation. Description of, the instruments, methods of measure•. ments and the conversion of the observed values to appro-priate quantities etc., are given in view of the above requirements. It is to be emphasized that a realistic and scientific installation of, instruments and observations on them,starting from the construction stages itself can reveal the real behaviour of the structure...