基于热量收支平衡原理的多年冻土区热棒路基设计计算方法

Design method of the thermosyphon embankment in permafrost region based on principle of heat balance

热棒是多年冻土区对路基进行热防护的重要措施之一,但相关规范中没有给出热棒路基的设计计算方法,已建热棒路基的设计主要是借鉴以往的工程经验。通过现场监测与计算,分析了冻土路基的热量收支特征,发现冻土路基在暖季处于吸热状态,而在寒季处于放热状态,年内总体处于吸热状态。地基多年冻土融沉的本质原因是路基的吸热量大于放热量导致的热量正积累。基于此,从路基热量收支平衡的角度出发,提出了一种新的热棒路基设计计算方法,其基本原理为确保热棒年内放热量不小于路基的年净吸热量。对青藏高原多年冻土区的热棒路基进行了现场试验监测,结果表明,热棒路基的沉降量明显小于普通路基的沉降量,热棒路基提高了地基多年冻土的稳定性,控制住了路基沉降变形。提出的热棒路基设计计算方法理论明确,参数获取简便,具有较强的工程应用价值,可在多年冻土区热棒路基设计中推广使用。

Thermosyphon is one of the important measures for thermal protection of the embankment in permafrost region.But the design method of the thermosyphon embankment is not provided in relevant standards.Therefore,the design of the existing embankments with thermosyphon mainly depends on the past engineering experience.Through field monitoring and theoretical calculation,the characteristics of heat exchange balance for the embankment in frozen soil region were analyzed.It was found that the embankment absorbs heat in warm season,but releases heat in cold season,and it was in the endothermic state for the whole year.The essential reason of the embankment thawing settlement is that the heat absorption is greater than heat release.A new design method of thermosyphon embankment was proposed based on the theory of heat balance.Its basic principle is to ensure the thermosyphon annual heat transmission capacity which is not less than the embankment net heat absorption.Taking the highway engineering in permafrost region of Qinghai-Tibet Plateau as an example,the design method proposed in this paper was verified by field test.The results show that the settlement of the thermosyphon embankment designed using the proposed method was significantly less than that of the ordinary ones.The thermosyphon embankment has improved the stability of the underlying permafrost and mitigated the settlement of the foundation permafrost.That verified the correctness and rationality of the method proposed in this paper.This method has clear theory,simple parameter acquisition and strong engineering application value,which can be widely used in design of the thermosyphon embankment in permafrost region.