## 3 Results and Discussion
### Impact of Synchronous Cooling Zone on the Temperature Stress of the Dam Body  
Both the climate conditions and material parameters have adverse impacts on the temperature control and crack prevention of concrete, so only optimization and improvement of temperature control measures can be conducted. The synchronous cooling zone's research is conducted to optimize the cooling process and scope based on the longitudinal joint arrangement. It decreases the temperature gradient in the dam's height, the temperature difference between the upper and lower layers of concrete, and the reciprocal constraint and temperature stress. Although the elastic modulus of concrete gradually increases with age, the leading cause of temperature stress is temperature change and constraint. The purpose of setting a synchronous cooling zone is to reduce the mutual restraint between the pouring layers. Figure 9 shows the temperature control measures and the spatial distribution of the cooling mode, while Figure 10 shows the dam foundation's casting process, strong constraint zone, and optimal cooling process control. Some definitions are introduced here:  
Phase 1 cooling in Figure 10 aims to reduce the concrete's peak value and control the maximum temperature of concrete. The purpose of medium cooling is to control the temperature rise after phase 1 cooling of concrete and reduce the cooling range of concrete during Phase 2 cooling by slowly cooling in the medium cooling stage; the purpose of Phase 2 cooling is to reduce the grouting temperature. 1. The height of a JX Dam grouting zone is 9 m, i.e., each grouted zone is 9 m in height;
2. Grouting zone: The zone where longitudinal joint grouting is to be carried out, generally one zone;
3. Synchronous cooling zone: The zone where cooling is carried out simultaneously and coordinately. When the grouting zone is the first grouted zone at the bottom of the constraint zone, the synchronous cooling zone is two grout zones above the grouting zone, while the other zones are a grout zone above the grouting zone;  
Figure 8: Temperature and stress envelop diagrams of dam middle section with longitudinal joint: (**a**) temperature envelop diagram of the middle section (Unit: \({}^{\circ}\)C); (**b**) stress along river direction of the middle section (Unit: 0.01 MPa). 4. Transition zone: The zone between the synchronous cooling zone and weighted cover zone, a grouting zone above the synchronous cooling zone;
5. Weighted cover zone: Newly placed concrete zone, a grouting zone above the transition zone. Figure 10: Forming process schematic of temperature gradient zones in the foundation constraint zone. Figure 9: Basic distribution diagram with the overflow section of the temperature control measures: (**a**) Distribution of Basic Temperature Control Measures; (**b**) Cooling Mode (synchronous cooling of 3 lower grouting zones). In scheme 1, the synchronous cooling zone is 9 m in height; in scheme 2, the synchronous cooling zone is 18 m in height; and in scheme 3, the synchronous cooling zone is 27 m.  
It can be seen from Table 5 and Figure 11 that:  
* When the synchronous cooling zone's height varies, it has a minimal impact on the maximum temperature. The maximum temperatures of the strong constraint zone are all 26.3 \({}^{\circ}\)C;
* If the synchronous cooling zone is 9 m in height (each grouted zone is 9 m in height), each grouting zone is cooled via cooling water. As the temperature difference and deformation between the upper and lower ground zones do not synchronize, the foundation concrete is under more vital constraints. The maximum stress in the middle of the strong constraint zone is up to 1.58 MPa, while cracks can be easily caused;
* If the synchronous cooling zone is 18 m in height, the two grouting zones are cooled in a coordinated manner. The constraint on foundation concrete is obviously reduced by reducing the temperature difference and synchronous deformation between the upper zone and the lower zone. The maximum stress in the middle position is 1.45 MPa.