# Influence of Monolith Length on Temperature Field of Concrete Gravity Dams
## 5 Discussion  
By analyzing previous research on the topic of thermal stress analyses of concrete dams, it was observed that the scope of the research on the monolith lengths of concrete gravity dams built using the block method is not wide enough. The problem of determining the monolith lengths has mainly been considered for gravity dams made of roller-compacted concrete (RCC). This research was conducted with the use of a phase thermal analysis based on the finite element method. With the above, all the relevant thermal contour conditions were considered (those on the surfaces between the blocks and the rock mass, those on the surfaces between previously poured and newly poured blocks, those on the surfaces of the blocks that were in contact with water and air, and the initial temperature of the concrete mixture), as well as the concrete hydration process. The conducted research describes, in more detail, the thermal behavior of the GBB, which was built using the block method during construction, the filling of the reservoir, and exploitation, and shows the influence of the monolith length (the distance between contraction joints) on the development of the temperature field. Figure 46: Concrete temperature changes in the middle of the section, in the upstream–downstream direction, at 170.50 m ASL for different monolith lengths (1804 th day—25 September of the 6 th year). Figure 47: Concrete temperatures in the horizontal section, in the direction of the dam’s axis, at 170.50 m ASL for different monolith lengths (1804 th day—25 September of the 6 th year). Gravity dams are built in monoliths that enable the operation of the joint, which allows the thermal stresses to be relieved and prevents the formation of cracks. The length of the monolith, the dimensions of the blocks, and the schedule of concreting were determined in the past by experience instead of by conducting a complex thermal stress analysis. The results of the conducted analysis improve the understanding of the thermal processes (which affect the development of thermal tension stresses) in concrete gravity dams, which could influence design decisions in order to increase the durability and reliability of these massive hydrotechnical objects. After concreting a block, it heats up due to the release of the heat of hydration. The heating of the concrete can be additionally supported by extremely high air temperatures for a long period of time. Subsequently, in the concrete-cooling process, which is evident in the results shown for both the construction process and the exploitation process, cracks may appear as a consequence of the volume-shrinkage process. The presented results also show a significant sensitivity of the temperature field to changes in the value of the monolith length. The above indicates the importance of controlling the temperature of the concrete (by carrying out measures during preparation as well as after pouring) under conditions of extreme temperatures, as well as the importance of choosing an adequate length for the monolith. In order to develop complete insight into the thermal stress behavior of the structure, a stress-deformation analysis of the developed models should be conducted. The disadvantages of the developed model are reflected in the omission of the dependence of the thermal and mechanical properties of the material on the temperature and the validation of the model by comparison with real temperature measurement data for the concrete during the construction and exploitation phases of the structure (it was not possible to implement it due to a change in the construction method). Variations in the block layout, the duration of concreting, the dependence of material thermal properties on the temperature and moisture content, the influence of solar radiation, and the use of pipe systems for cooling and curing concrete during construction can be considered comprehensive guidelines for improving the presented research or for further research.