现浇混凝土-冻土接触面传热特性影响因素研究

Influential factors on the heat transfer characteristics of interface between cast-in-place concrete and frozen soil

现浇混凝土-冻土接触面传热特性直接影响灌注桩表面冻结强度,研究现浇混凝土-冻土接触面传热特性影响因素对冻土区桩基础设计和施工具有重要意义。基于小型模型桩试验条件建立数值模型,开展混凝土浇筑过程中混凝土-冻土接触面传热特性研究,分析了混凝土浇筑温度、水胶比、冻土温度、冻土含水量引起的接触面热流和温度变化。结果表明:浇筑温度由5℃升高至30℃,0.5 h混凝土与冻土接触面热流增大381.2%.水胶比由0.4增大至0.6,0.5 h接触面热流减少23.7%.接触面温度随冻土含水量的增大呈先增大后减小趋势,峰值在冻土液限附近。导热系数和相变热作用的转变起到了决定作用。冻土温度在-1^-3℃之间降低时,接触面温度随冻土温度降低而升高。浇筑后0~1 h(尤其是0~0.5 h)是混凝土对冻土释放热量的主要时间。

The heat transfer characteristics of cast-in-place concrete-frozen soil contact surface directly affects the surface freezing strength of cast-in-place pile,and it is important to study the heat transfer characteristics of cast-in-place concrete-frozen soil contact surface for Pile Foundation design and construction in frozen soil area.Based on the small model pile test,a numerical analysis model is established to calculate the heat transfer characteristics during concrete poured in situ.The results show that the heat flow of 0.5 h concrete and the contact surface of frozen soil increases by 381.2%when the pouring temperature rised from 5 to 30℃.The water-cement ratio increased from 0.4 to 0.6,and the heat flux of 0.5 h contact surface is reduced by 23.7%.The temperature of the contact surface increased first and then decreased,and the peak is near the liquid limit of soil.When the temperature of frozen soil decreased from-1 to-3℃,the temperature of the contact surface increased with the decrease of the temperature of the frozen soil.The thermal conductivity and transformation of the thermal effect of phase transition have played a decisive role.0~1 h(especially 0~0.5 h)is the main time for the heat released from concrete to frozen soil.