人工热源在寒区路基中的热扩散特性及热影响范围研究

Study on thermal diffusion characteristics and influence range of an artificial heat source inside embankment in cold regions

针对寒区铁路路基冻胀病害,提出一种基于地源热泵的供热系统及分布式方案,设计I级单线铁路的足尺半幅路基试验平台,对路基温度场进行监测与分析。定义供热系统的有效热影响半径为在一定时间内将路基冻结深度控制在有害临界值以内的纵向范围,并提出有效热影响半径的预测方法。结果表明:热泵系统的供热温度可达30℃以上,制热系数(COP)可达6.9,在寒冷气候下具有稳定的地温能转化性能与节能性。有效供热量和COP随着时间的延长而逐渐减小。土体升温幅度随着与热源距离的增大而降低,且路基竖向升温速率大于纵向。人工供热对寒潮天气影响具有显著的抑制作用,试验结束时供热系统两侧2.0和3.0 m范围的冻结深度控制分别在30和35 cm以内。有效热影响半径与供热时间和有害冻结深度均呈正比关系。当有害冻结深度为30,35,40 cm,供热5 d时的有效热影响半径分别为0.44,0.64,0.83 m;若热影响半径需达到1.5 m,所需供热时间分别为53,41,35 d。实际应用时应根据路基有害冻结深度和冻胀处置时间要求,合理设计供热系统沿线路的纵向布设间距,以保证供相邻供热系统的解冻范围在规定时间内交汇。

In order to address the frost heave problem of railway embankment in cold regions,an artificial heating system and a distributed heating scheme based on ground source heat pump technology was proposed.A full scale half-width embankment test platform of class I single-track railway was built,and the temperature field of embankment was monitored.The effective heating influence radius of the heating system was defined as the longitudinal range within which the embankment freezing depth is controlled below the harmful threshold within a certain time,and a prediction method of the effective heating influence radius was put forward.The test results show that the heating temperature of the heat pump system can reach above 30℃,the coefficient of performance(COP)can be as high as 6.9,and both the effective heating capacity and COP gradually decrease with time.The temperature rise amplitude of soil decreases with the distance from heat source,and the temperature increment rate in the vertical direction around the heating pipe is greater than that in the longitudinal direction along embankment.Artificial heating has a significant inhibitory effect on the impact of cold wave weather.At the end of the test,the freezing depth within 2.0 and 3.0 m on both sides of the heating system is controlled within 30 and 35 cm respectively.The heating influence radius is proportional to both heating time and the harmful freezing depth threshold.When the harmful freezing depth threshold is 30,35,40 cm,the effective heating influence radius is 0.44 m,0.64 m,0.83 m respectively when heating for 5 days;and if the heating influence radius needs to reach 1.5 m,the heating time should be 53,41,35 d respectively.In application,the longitudinal layout spacing of heating systems along the embankment should be reasonably designed according to the harmful freezing depth threshold and the required treatment time after the appearance of frost heave,so as to ensure the merge of thawing range of adjacent heating systems within the specified time.