Zhang Guozhu, Cao Ziming, Liu Yiping, Chen Jiawei
Institute of Geotechnical Engineering, Southeast University, Nanjing 211189, China.
Jiangsu Key Laboratory of Urban Underground Engineering & Environmental Safety, Southeast University, Nanjing 211189, China.
Sensors (Basel). 2021 Jun 4;21(11):3873. doi: 10.3390/s21113873.
Investigation on the long-term thermal response of precast high-strength concrete (PHC) energy pile is relatively rare. This paper combines field experiments and numerical simulations to investigate the long-term thermal properties of a PHC energy pile in a layered foundation. The major findings obtained from the experimental and numerical studies are as follows: First, the thermophysical ground properties gradually produce an influence on the long-term temperature variation. For the soil layers with relatively higher thermal conductivity, the ground temperature near to the energy pile presents a slowly increasing trend, and the ground temperature response at a longer distance from the center of the PHC pile appears to be delayed. Second, the short- and long-term thermal performance of the PHC energy pile can be enhanced by increasing the thermal conductivity of backfill soil. When the thermal conductivities of backfill soil in the PHC pile increase from 1 to 4 W/(m K), the heat exchange amounts of energy pile can be enhanced by approximately 30%, 79%, 105%, and 122% at 1 day and 20%, 47%, 59%, and 66% at 90 days compared with the backfill water used in the site. However, the influence of specific heat capacity of the backfill soil in the PHC pile on the short-term or long-term thermal response can be ignored. Furthermore, the variation of the initial ground temperature is also an important factor to affect the short-and-long-term heat transfer capacity and ground temperature variation. Finally, the thermal conductivity of the ground has a significant effect on the long-term thermal response compared with the short-term condition, and the heat exchange rates rise by about 5% and 9% at 1 day and 21% and 37% at 90 days as the thermal conductivities of the ground increase by 0.5 and 1 W/(m K), respectively.
预制高强混凝土（PHC）能源桩的长期热响应研究相对较少。本文结合现场试验和数值模拟，对层状地基中PHC能源桩的长期热性能进行了研究。从试验和数值研究中获得的主要结果如下：首先，热物理地基特性逐渐对长期温度变化产生影响。对于热导率相对较高的土层，靠近能源桩的地温呈缓慢上升趋势，距PHC桩中心较远位置的地温响应似乎有所延迟。其次，通过提高回填土的热导率，可以增强PHC能源桩的短期和长期热性能。当PHC桩中回填土的热导率从1 W/(m·K)增加到4 W/(m·K)时，与现场使用的回填水相比，能源桩在1天时的换热量可分别提高约30%、79%、105%和122%，在90天时可分别提高20%、47%、59%和66%。然而，PHC桩中回填土的比热容对短期或长期热响应的影响可以忽略不计。此外，初始地温的变化也是影响短期和长期传热能力以及地温变化的一个重要因素。最后，与短期情况相比，地基的热导率对长期热响应有显著影响，当地基热导率分别增加0.5 W/(m·K)和1 W/(m·K)时，1天时的换热率分别提高约5%和9%，90天时分别提高21%和37%。
