低液限黏土冻结热物理参数及热传导模型试验研究

Experimental study on thermophysical parameters and heat conduction model of low liquid limit clay during freezing

为了研究不同温度条件下饱和度、比热容、相变潜热、未冻水含量等对人工冻结法的影响,以昆明地铁联络通道冻结法施工为背景,将该地区低液限黏土作为研究对象开展试验,探明了未冻水含量、热物理参数的变化规律;建立了正交球缺接触热传导模型并对照室内试验结果进行验证。结果表明:当温度持续降低到某温度范围(-15~-8℃)时,土中未冻水含量变化不大,据此可优化降温计划;在负温段,不同饱和度试样未冻水含量与相变潜热呈负相关,饱和度与相变潜热正相关;导热系数与比热容随温度的变化表现为两个阶段,并在0~-10℃温度范围内迅速降低后趋于平稳;所建立的正交球缺接触热传导模型能可靠计算任意时刻未冻水量并预测热物理参数变化趋势,可为减少冻结工作中热物理参数的测量工作量提供参考。

In order to study the influence of saturation,specific heat capacity,latent heat of phase change and unfrozen water content on the artificial freezing method under different temperature conditions,the low liquid limit clay in the area was taken as the research object to carry out the experiment based on the freezing method construction of Kunming subway contact passage,and the variation law of unfrozen water content and thermophysical parameters was explored.An orthogonal ball-missing contact heat conduction model was established and verified by laboratory test results.The results show that when the temperature continues to drop to a certain temperature range(from-15℃to-8℃),the content of unfrozen water in soil does not change much,so the cooling plan can be optimized.In the negative temperature section,the unfrozen water content of the samples with different saturation is negatively correlated with the latent heat of phase transition,and the saturation is positively correlated with the latent heat of phase transition.The change of thermal conductivity and specific heat capacity with temperature is manifested in two stages,and decreases rapidly in the temperature range from 0℃to-10℃and then becomes stable.The established orthogonal spherical contact heat conduction model can calculate the amount of unfrozen water at any time and predict the change trend of thermal physical parameters,which can provide reference for reducing the measurement workload of thermal physical parameters in freezing work.