Influence of Monolith Length on Temperature Field of Concrete Gravity Dams

This paper examines the influence of monolith length on the temperature field of concrete gravity dams built using the block method. The developed 3D model is capable of conducting a thermal analysis of a 95.0 m high concrete gravity dam built using the block method, where each newly cast block represents a new analysis phase. The calculation accounts for the period of construction, the filling of the reservoir, and the service for a total duration of about 5 years. The thermal properties of the material, the influence of cement hydration heat, the temperature of the surrounding rock mass, the temperature of the fresh concrete mixture, and the corresponding boundary conditions defining a heat transfer were taken into account. The height and width of the blocks, as well as the sequence of concreting, were considered invariable, while the length of the blocks (dimension in the direction of the dam's axis equal to the monolith length) varied, with values of 10.0, 12.5, 15.0, and 20.0 m. The obtained calculation results for the control nodes showed that the maximum reduction in the monolith length (from 20.0 m to 10.0 m) caused a decrease in the maximum temperature values of the concrete (from 1.6 to 3.4 degrees C, depending on the control node). Also, the results showed that, by reducing the length of the monolith, there was a delay in the moment at which the maximum temperature values of the concrete appeared in the selected control node. The delay in reaching the maximum, in relation to the 10.0 m long monolith, was from 7 days (for points on the crest dam) to 49 days (for points in the central zone of the monolith) for the other considered monolith lengths. The above indicates the importance of concrete temperature control for longer monoliths, especially during construction in extreme air temperatures. The main contribution of the conducted analysis is the development of insight into temperature field changes depending on monolith length, which can help engineers during the design and construction of new, as well as the maintenance of existing, dams.