Thermal Stress Sensibility For Construction Scheme Of Impervious Face-slab Of RCC Dam

According to observations of some existing RCC dams at home and abroad, the RCC dam construction technologies are successful in general, but the problems of seepage still exist. These problems damage the durability and appearance of RCC Dams and lead to the water of reservoirs run off. Therefore the impervious face-slab set on upstream face of dam is a key to seepage control of RCC Dams. And the value of impervious face-slab is showed by the impervious effect.The reinforced concrete face-slab is adopted as impervious body by Long Tan RCC Dam. Based on the analysis of information about the cracks of impervious concrete face-slab which has been grasped, thermal stress is important one among many reasons which contribute to the cracks of concrete face-slab. The relation between the thermal stress and construction operation procedure is close. So it has practical meaning to study the influence of different reinforced concrete face-slab construction schemes on the temperature field and thermal stress field of reinforced concrete face-slab.Based on the heat conduction theory, the FEA theoretical formulas of temperature field and thermal stress are deduced in this paper. 3-D finite element floating mesh method is adopted and relevant programs are compiled.Examples are given and the results have proved the method is reasonable and the programs are reliable. Through calculating and analyzing the temperature field and thermal stress field of two different construction schemes of Long Tan RCC Dam' s reinforced concrete face-slab, the paper studies the influence of the two construction schemes - synchronous rise and asynchronous rise scheme - on the temperature field and thermal stress field of reinforced concrete face-slab. In the paper, not only such factors as reinforcing steel bar, various placing temperature of concrete in case of lift placements, lift thickness, time interval between lifts, the variation of elastic modules of concrete, heat of hydration, the temperature changes of environment but the effect of creep deformation and autogenous volume change on the temperature field and thermal stress field of reinforced concrete face-slab are considered. Computation and analysis conclude that the thermal stress of asynchronous rise scheme is far smaller than that of synchronous rise scheme, so asynchronous rise scheme should be recommended.