Simulation And Analyses Of The Thermal Stress Of The RCC Dam With Artificial Short Joint

It is the bottleneck problem at all time for thermal stress and temperature control in the construction of mass concrete structure, such as water retaining dam. Thermal stress is one of the most serious reasons for cracking in dams. Although the hydration heat in RCC dam is lower than that in normal concrete dam, it is inevitably to exist the problems of thermal stress owing to its material and construction characteristics. It exists the region of high stress and the value of tension stress is higher in somewhere near by dam heel especially in the action of dead weight and water pressure. The adoption of the complicated measure of temperature control should evidently increase the cost and have great influence on the construction schedule of the engineering. This paper studies a horizontal artificial short joint which is set near by the dam heel in the early stage of dam construction. Its primary function is releasing the tension stress and using the artificial stable joint at prescriptive part instead of the unstable joints which are stochastic and generated by structural stress.In this paper, the 3-D finite element relocating mesh method is used to calculate the thermal stress field , and the contacting element model is used to simulation the artificial short joint of the dam. According to heat conduction theory, elastic creep theory, finite element theory and contacting element calculation theory, the 3-D finite element simulation program for RCC dam is worked out to simulate the temperature field and the thermal stress field of the RCC dam with the artificial short joint. In the program, the effect of lamination placement, construction interval, the change of modulus of elasticity, the adiabatic rise of temperature, the change of ambient temperature, concrete creep and the dam with joints on temperature field and thermal stress field are considered.Through a typical example of simulation and analyses of temperature field and thermal-creep-stress field in RCC dam with and without the artificial short joint during construction stage and operating period, this paper systematically studies the influence of the artificial short joint on the stress field. The results indicate that the artificial short joint can evidently reduce the tension stress near by the dam heel, but it brings the region of the tension stress into the interior of the dam, so adequate measures must be adopted near by the joint to avoid cracks developing. The results indicate that the program is correct and of great utility.