Simulation And Research On Temperature Control Of RCC Arch Dam

With the rapid development of RCC dam construction technology, all kinds of RCC archdam is springing up both in China and abroad. The resulting problem is the dam cracking afterits operation. Because of most cracks of RCC arch dam are caused by temperature stress, ithas become an important subject in the development of RCC arch dam that how to use thetemperature control measures to prevent cracks during construction. The temperature stressand temperature control measures of RCC arch dam have their own characteristics. Comparedwith normal concrete, the material parameters and construction methods of RCC are verydifferent, what’s more, compared with gravity dam, arch dam cannot remove the constraintsby dam temperature deformation in axis direction, a larger temperature stress will beproduced within the dam. Considered the effect of arch dam construction process and externalfactors comprehensively, several kinds of temperature control measures is simulated byANSYS, the research contents are as follows:(1) Based on one double-curvature RCC arch dam project, considered the factors suchas outside temperature, water temperature, concrete hydration heat, summer shutdown and soon, the whole temperature field which from construction to operation is obtained by the finiteelement numerical analysis; Synthesized the change of dam’s weight and concrete’s elasticmodulus during construction process, and the change of water pressure during storage process,the whole casting and operation process of dam is emulated, the development process of thestress field under the main influence of temperature field is obtained.(2) According to the temperature and stress control standard of RCC arch dam, theproblems in the absence of temperature control measures are analyzed, the reasons andpositions that the dam cracks may occur are discussed. It shows that the internal temperatureof dam is higher without temperature control measures, the highest temperatures during theconstruction are all higher than28℃, while the outside surface is with low temperature underinfluence of external factors, it lead to a temperature difference between inside and outsidethat higher than control standard; Because of a long concreting intermission time and passingflood, the temperature difference between upper and lower is large in the old-new concrete interfaces that formed by stages; Due to the gravity function and the constraint of the bedrockon both sides, the larger tensile stress appears on the upper arch abutment, the dam shouldersare in tension, especially in the old-new concrete interfaces, it appears the maximum tensilestress(1.7MPa); The location of the larger compressive stress is close to the shoulders of theunderlying bedrock, while the compressive stress value is less than the allowable compressivestress.(3) By analyzing the problems mentioned above, corresponding temperature controlmeasures is formulated, and the plans is proposed according to the different factors affecting,then the temperature variation with time and temperature control effect are compared bysimulation analysis, finally the characteristics of these temperature control measures aresummarized, also the best temperature control schemes are found. The results show that theheat preservation measures on upstream and downstream surface make the dam’s surfacetemperature increase about13℃, the temperature difference between inside and outside isreduced effectively, the probability of surface cracks is reduced; Took heat preservation andheat insulation measures on the old-new concrete interfaces with polyethylene foam plasticboard, the temperature difference between upper and lower is reduced effectively; Took waterpipe cooling measures, the highest temperature within dam is decreased by5to10℃, dam’stemperature is under control, it is beneficial to reduce the inside and outside temperaturedifference and temperature stress; It is a direct and effective temperature control method thatreduce concrete pouring temperature, each lower2℃, the highest temperature within dam isdecreased by0.2to0.9℃.(4) Synthesizing the best solution of the above temperature control measures, thesimulation calculation is performed, the dam temperature and stress distribution are gottenunder the best effect of temperature control, the results show that the highest temperature isreduced by11℃, the maximum tensile stress is decreased by0.47MPa, distribution of Misesequivalent stress is uniform, the reduced value is an average of0.2MPa, and the compositemeasures keep the various temperature differences and stress under standard ranges.Comparing the effects of these measures, the maximum tensile stress in the compositemeasures is decreased by22.27%in each period, the effect of pipe cooling measure is verysignificant in each period, and surface heat preservation measure is the best during theshutdown and flood season.