Accurate and fast measurements of thermal properties are frequently required for characterizing the heat-water dynamics in frozen soil. Measuring the thermal properties of frozen soil without inducing ice thaw has proven challenging with conventional heat pulse (HP) methods. In this study, based on an Infinite Line Source (ILS) semi-analytical model that applies a constant temperature lower than the freezing point at the heat source to prevent the initiation of ice thaw in the frozen soil, we propose a novel HP-based approach to measure thermal properties, applicable at temperatures below or above 0°C. Laboratory experiments and numerical modeling were utilized to validate the applicability of the approach and optimization strategies of the measurement. We found that the proposed HP-based approach effectively maintained the maximum spatial temperature below the freezing point and therefore estimated the bulk thermal properties of quartz sand and ice contents. An optimized measurement strategy was proposed to monitor the temperature variations 2–4 cm away from the center of the heat probe after 60 s. This progress can largely facilitate the determination of the thermal properties of multi-phase and -component frozen soil such as thermal conductivity, heat flux, and ice content in cold areas across soil science, hydrology, engineering, and climate science.

中文翻译：

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一种确定冻土中“有效”热特性的新型热脉冲方法


为了表征冻土中的热-水动力学，通常需要准确和快速的热特性测量。事实证明，使用传统的热脉冲 （HP） 方法在不诱导冰融化的情况下测量冻土的热特性具有挑战性。在这项研究中，基于无限线源 （ILS） 半解析模型，该模型在热源处施加低于冰点的恒定温度以防止冻土中开始冰融化，我们提出了一种基于 HP 的新型方法来测量热性能，适用于低于或高于 0°C 的温度。 利用室内实验和数值建模验证了该方法的适用性和测量的优化策略。我们发现，所提出的基于 HP 的方法有效地将最高空间温度保持在冰点以下，从而估计了石英砂和冰含量的体热特性。提出了一种优化的测量策略，以监测 60 s 后距离热探针中心 2-4 cm 的温度变化。这一进展可以在很大程度上促进土壤科学、水文学、工程学和气候科学中寒冷地区多相和组分冻土的热特性的测定，例如导热系数、热通量和冰含量。