Temperature Control Study For Crack Prevention Of Mamaya-i High Mixing Fly Ash RCC Gravity Dam

Mamaya I hydropower station is the second level of cascade development which islocated in BeipanRiver mainstream,and the dam site is in the temperate zone.Theretaining structure is RCC gravity dam, with the height of109m and the crest elevationof592m. The dam body is equipped with three surface outlets and constructed withhigh mixing fly ash roller compacted concrete,the maximum content of fly ash is70%.the dam’s concrete-pouring period is planned to be nineteen months.Dam’s surface oftemperature control for crack prevention is confronted with the following problems: thecomplex dam structure, fast rising, high temperature of the dam site, large temperaturedifference, and water-cooled strike on the dam’s surface by overflowing duringconstruction period. All of the problems are needed to be solved by simulating variousboundary conditions and the dam’s construction process, performing the finite elementcalculation, and carrying out study on temperature control for crack prevention, andfinally proposed temperature control measures for dam construction.The temperature is calculated by ANSYS finite element software combined withsimulation of temperature fields at the typical dam section (overflow dam section)during the whole process of construction period and impoundment period oftemperature field simulation. The stress field is simulated by secondary developmentprogram. And then, analysis on dam’s temperature fields and creep stress state isperformed to find out the economical and reasonable temperature control scheme,which can meet the need of dam’s concrete crack prevention.Three-dimensional finite element model is established for overflow section basedon the collected data in this project including geology, hydrology, meteorology,materials, construction schedule and so on. The standard for temperature and stress isdetermined according to water conservancy specification. The quasi stable temperaturefield of the typical dam section is calculated by simulation of the air temperature andreservoir’s water temperature. The pouring plan for each rolling lift of the dam and theimpoundment plan are made based on construction schedule and flood control schemein this project, and the pouring temperature for each rolling lift is formulated bytemperature control measures. Temperature and stress simulation at each typical dam section is firstly performed without using the temperature control scheme, in whichcondition we analyze whether the concrete at each part of the dam and different agesmeet the criteria of stress control or not. The dam part which does not meet with thecriteria is treated with the measures of temperature control such as controlling pouringtemperature, water cooling and so on. And then the temperature and stress simulationis performed again until the dam’s temperature and stress meet the requirements of thespecification.The subsequent temperature control measures will be put forward according to the measured data during the construction period and the applicability analysis of temperature control measures.The temperature control simulation of both ordinary mixing and high mixing of flyash concrete shows that the high mixing fly ash concrete has good promotion value, forits low adiabatic temperature rise, small mechanics performance difference, obviousadvantage in temperature control,energy efficiency and environmentalprotection.Through analysis on the development status of temperature control of mass concrete and its prospects for development.