用于寒区心墙冬季施工的相变黏土热学性能研究

Investigation on thermal properties of core-wall clay incorporated with phase change material for winter construction in cold regions

寒区土石坝心墙土料冬季施工经常会受到冻融问题的困扰,而常规保温措施会干扰施工过程,且施工有效时间较短。相变黏土(PCM-clay)可在不干扰正常施工的条件下防止心墙土料发生表层冻结,从而延长寒区土石坝冬季施工时间。在相变黏土的防渗、强度等性能符合心墙功能的前提下,本文对其热学性能进行研究,分析了相变材料(PCM)掺量对其热学参数的影响机制,建立了潜热、导热系数和比热的均质化等效模型,并将其用于寒区冬季施工条件下的控温性能数值模拟,以验证相变黏土控温效果的有效性。结果表明:相变黏土的潜热主要受PCM掺量与结晶度控制;其导热系数和比热随PCM掺量的增加而减小;通过相变传热模型可以有效模拟控温过程,从而为进一步分析相变黏土的控温效果提供依据。

During the core-wall clay construction of an earth-rock dam in cold regions,the freeze-thaw impact on core-wall clay is a major challenge.Conventional anti-freezing measures slow down normal construction process because of their serious interference with core-wall clay compaction.The core-wall clay incorporated with phase change material(PCM-clay)is able to ensure its surface temperature above the freezing point,consequently extending the winter construction time of earth-rock dams in cold regions and avoiding construction interference.This paper investigates the thermal properties of PCM-clay,based on the feasibility of using it as core-wall clay(i.e.,permeability and mechanical strength).We analyze the impact mechanism of PCM content on these thermal parameters,and develop homogenized models to estimate the thermal parameters of PCM-clay(i.e.,latent heat,thermal conductivity and specific heat).Numerical analysis based on these models is used to verify the effectiveness of PCM-clay in temperature control for winter construction of earth-rock dams in cold regions.Results indicate that the latent heat of phase change clay is dominated by the PCM content and its crystallinity,and the thermal conductivity and specific heat are both negatively correlated with the PCM content.Numerical models based on the phase change heat transfer theory can provide reliable simulation of temperature history,which is useful in further research of temperature control with PCM-clay.