# Optimization Method for Improving Efficiency of Thermal Field Reconstruction in Concrete Dam
## 4 Case Study
### Effectiveness Evaluation  
The extreme maximum temperature in the WDD reservoir is 42.7 \({}^{\circ}\)C, the extreme minimum temperature is \(-\)5.8 \({}^{\circ}\)C, and the annual average temperature is 20.9 \({}^{\circ}\)C. During the period of construction, the concrete pouring volume can reach 100 m\({}^{3}\) per hour. Considering multiple factors such as the complex environment and the large volume of concrete pouring, WDD's temperature control had a high standard. The maximum temperature of concrete must not exceed 27 \({}^{\circ}\)C in the area constrained by the dam foundation and 30 \({}^{\circ}\)C in other areas. Three stages were stipulated for cooling down. The target temperature after the end of the first stage was between 23 \({}^{\circ}\)C and 25 \({}^{\circ}\)C. In the second stage, the cooling rate was required to be 0.3 to 0.5 \({}^{\circ}\)C/day, and the target temperature after the end of this stage was between 18 \({}^{\circ}\)C and 21 \({}^{\circ}\)C. The target temperature after the end of the third stage was between 13 \({}^{\circ}\)C and 16 \({}^{\circ}\)C.  
To meet the above temperature control requirements, an intelligent cooling control system (ICCS) for concrete temperature control was implemented in the WDD dam construction, combining water-cooling pipes with thermal field reconstruction. Contractors can log in to the intelligent temperature control system via their mobile phones to query the real-time thermal field of each concrete block, which provides a real-time judgment basis for the evaluation of the concrete temperature control effect. This methodology surpasses traditionally used numerical simulations and analyses that lag far behind construction  
Figure 15: Project overview of the WDD dam. (**a**) Upstream; (**b**) downstream.  
progress. The maximum temperature of the concrete did not exceed the temperature control requirements, and a great temperature control effect was achieved (Figure 16a,c). The engineering application procedure summarized in Section 3.4 was applied in the ICCS (Figure 16b), and the thermal field was reconstructed.  
The 7#-011 concrete block was taken as an example. The real-time thermal field was reconstructed based on the proposed method and used to guide the cooling strategy. The optical fibers were not embedded in the 6#-010, 8#-009, and 9#-012 concrete blocks, serving as the control group. The cooling strategy for these three blocks can only rely on three digital thermometers to obtain the temperature during water cooling, rather than using the proposed method to calculate the thermal field.  
By comparing the actual temperature curve of the 6#-010, 7#-011, 8#-009, and 9#-012 blocks, the maximum temperature of the 7#-011 block was significantly lower than the other three, which was 25.4 \({}^{\circ}\)C (in line with the temperature control requirement) (Figure 17). The maximum cooling rate of the 7#-011 block was 0.4 \({}^{\circ}\)C/d, which also met the temperature control requirement. In addition, the temperature curve of the 7#-011 block was smoother, meaning that the water-cooling strategy for the 7#-011 block was more effective than the other three, and the temperature difference was much lower. Due to the real-time thermal field reconstruction, the cooling strategy was able to be adjusted in time, the temperature stress was well controlled, no temperature cracks appeared, and precise temperature control was achieved. The successful application of the proposed method guaranteed the construction quality of the WDD dam, and, on 16 June 2021, all 12 water turbines were put into operation.  
Figure 16: Temperature control effect based on the thermal field reconstruction results. (**a**) Observed maximum temperature; (**b**) the ICCS incorporating the thermal field reconstruction; and (**c**) the ICCS.