# Study on the Effect of Insulation Materials on the Temperature Field of Piles in Ice-Rich Areas
## 4 The Effect of Insulation on the Temperature Field of Pile Foundation
### Effect of Insulation Thickness on the Temperature Field of Pile Foundation  
Five scenarios were used to study the effect of different insulation layer thicknesses on the temperature of the pile foundation. Keeping the thermal conductivity coefficient of the insulation layer and other thermal physical parameters unchanged, the thickness of the insulation layer was set as 0 cm, 5 cm, 10 cm, 15 cm, and 20 cm, and the calculated results of the temperature field on the pile side were taken for analysis. Figure 7 shows the effect of the insulation thickness on the pile body temperature at different periods. In the upper part of the pile, the temperature was low due to the influence of atmospheric temperature. The heat passes through the top of the pile to the atmosphere by heat conduction. Upon increasing the depth, the insulating effect of the insulation layer gradually became stronger. At a depth of 5 m, the temperature of the pile was basically unaffected by the atmospheric temperature. At 7 d, the temperature of the insulation in the thickness range of 0-20 cm was 3.0 \({}^{\circ}\)C, 10.0 \({}^{\circ}\)C, 15.6 \({}^{\circ}\)C, 16.9 \({}^{\circ}\)C, and 19.9 \({}^{\circ}\)C at a depth of 7.4 m. At 28 d, the temperature of the insulation within the thickness range of 0-20 cm was \(-\)1.1 \({}^{\circ}\)C, \(-\)0.5 \({}^{\circ}\)C, 0.7 \({}^{\circ}\)C, 1.4 \({}^{\circ}\)C, and 1.6 \({}^{\circ}\)C. In the same period, the pile temperature increased with the thickness of the insulation layer. The use of insulation also reduces the lateral heat flow during the release and refreeze phases of concrete, weakening the thermal disturbance of the concrete ecotherm to the perimeter of the pile in the frozen soil. Figure 8 shows that upon increasing the insulation thickness, the maximum temperature of the pile body was elevated, and the rate of refreezing became slower. The temperature of the pile body fell below 0 \({}^{\circ}\)C at 16 d for the pile foundation without filling in the insulation layer. The temperature of the pile body eventually reached 0 \({}^{\circ}\)C after adding the insulation layer, and the thicker the thickness of the insulation layer, the longer it took for the pile body to reach 0 \({}^{\circ}\)C. Adding insulation during the early stages of concrete placement can slow the rate of heat dissipation and significantly increase the temperature  
Figure 6: 0–50 d pile core temperature value. of the pile. Therefore, the pile will be at a more appropriate maintenance temperature for a long time, which is conducive to ensuring the early strength formation of concrete. When the concrete temperature dropped to 0 \({}^{\circ}\)C, the water inside the concrete began to freeze, which reduced the strength of the concrete at a later stage. If the concrete can be precured to a certain strength before freezing, its late compressive strength loss will be reduced. Generally, the freezing of concrete late compressive strength loss within 5% of the pre-cured strength value is taken as the \"concrete frozen critical strength\" [20]. The \"Construction Engineering Winter Construction Regulations\" (JGJT104-2011) were developed to make the winter construction of construction projects safe, economical, and environmentally friendly, which explains the concrete frozen critical strength. This experiment was conducted in winter. According to calculations performed according to \"Construction Engineering Winter Construction Regulations\" (JGJT104-2011), an insulation thickness of 5 cm is sufficient to ensure that the critical strength of concrete used in the project is reached. Figure 9 shows that the ratio of pile temperature to thickness is greater than 1 when the insulation layer  
Figure 8: 0–50 d temperature of pile body with different insulation layer thickness. Figure 7: Temperature field of pile body with different insulation layer thickness. is 0-10 cm thick.