Yu Dezhong, Cao Yang, Zhao Qianqian
College of Urban Construction, Zhejiang Shuren University, Hangzhou, 310015, Zhejiang, China.
College of Water Conservancy and Civil Engineering, Northeast Agricultural University, Harbin, 150080, Heilongjiang, China.
Heliyon. 2024 Jul 27;10(15):e35252. doi: 10.1016/j.heliyon.2024.e35252. eCollection 2024 Aug 15.
To determine the cooperative variation laws of temperature fields in bridge concrete piles and the surrounding frozen soil during the freezing process in high-latitude, low-altitude insular permafrost regions, we utilized a practical bridge construction project within the frozen soil area of the Daxing'an Mountains, China. This served as the foundation for developing a method to remotely and dynamically monitor the temperatures of piles and soil in permafrost regions, enabling continuous, automatic monitoring of pile-soil temperature data. Employing this automatic temperature monitoring system, we collected temperature data from two 15-m-long concrete bored piles before and after freezing, and monitored the freezing process of the pile foundations in real-time. The cooperative variation laws of the pile-soil temperature field over time were summarized, and a calculation equation for the pile foundation's freezing time was established based on finite element analysis results. Monitoring and analysis reveal that under the influence of the frozen soil temperature field, the pile foundation initially freezes from the bottom up in a unidirectional manner. When the atmospheric temperature falls below 0 °C, the pile foundation freezes simultaneously from both the upper and lower directions. Post-freezing, the internal temperature of the pile body aligns with the surrounding soil temperature, with a temperature difference of less than 0.1 °C at the same depth. For similar in-place temperatures, the freezing time for a test pile with a 1.2m diameter is 1.14 times that of a 1.0m diameter test pile. The range of the hydration heat effect of cement concrete extends 1-2 times the pile diameter.
为确定高纬度、低海拔岛屿多年冻土区桥梁混凝土桩与周边冻土在冻结过程中温度场的协同变化规律，我们利用了中国大兴安岭冻土区的一个实际桥梁建设项目。这为开发一种远程动态监测多年冻土区桩与土壤温度的方法奠定了基础，能够持续、自动地监测桩土温度数据。采用该自动温度监测系统，我们采集了两根15米长混凝土灌注桩冻结前后的温度数据，并实时监测了桩基的冻结过程。总结了桩土温度场随时间的协同变化规律，并根据有限元分析结果建立了桩基冻结时间的计算方程。监测与分析表明，在冻土温度场的影响下，桩基最初从底部向上单向冻结。当大气温度降至0℃以下时，桩基从上下两个方向同时冻结。冻结后，桩身内部温度与周边土壤温度一致，同一深度处温差小于0.1℃。对于原位温度相似的情况，直径1.2米的试验桩的冻结时间是直径1.0米试验桩的1.14倍。水泥混凝土水化热效应的范围延伸至桩径的1 - 2倍。
