Abstract
Thermal conductivity of soils is a crucial characteristic in various geotechnical applications, such as geothermal pumps, energy piles and buried pipelines. Previous researchers have done extensive works on the factors that may affect the soil thermal conductivity, including soil porosity, degree of saturation, mineralogy, testing temperatures, particle size and gradation. A modified oedometer frame that can incorporate the transient heat probe method is adopted to investigate the influence of stress state on thermal conductivity of Toyoura sand. Preliminary test under 1-D compression shows that the thermal conductivity of sand increases with the rise of vertical stress, and the variation exhibits hysteresis during a loading and unloading cycle. In addition, the effects of void ratio and water content were also studied and test results agreed well with previous values reported in the literature.
Highlights
Due to the increasing cost of energy and the environmental impacts of burning fossil fuels for energy, geothermal structures and energy technologies are gaining more and more attentions
This paper presents some preliminary test results regarding the stress effect on thermal conductivity, through a series of measurements carried out on a standard material, Toyoura sand
Thermal conductivity of Toyoura sand was experimentally investigated using transient methods, where a thermal probe was inserted into soil specimens and temperature changes during heating and cooling process were recorded
Summary
Due to the increasing cost of energy and the environmental impacts of burning fossil fuels for energy, geothermal structures and energy technologies are gaining more and more attentions. One of the most important factors affect the performance of geo-energy sources or sinks is the thermal properties of soils [1], which governs the heat transferring or preservation in related projects. There has been extensive studies about the thermal conductivity of soils with a consideration of various factors, such as void ratio, degree of saturation, particle size, mineral component, salt concentration, microstructures, etc. The studies about the stress effect on the soil thermal conductivity are limited [14; 15]. This paper presents some preliminary test results regarding the stress effect on thermal conductivity, through a series of measurements carried out on a standard material, Toyoura sand. The influences of void ratio and water content were tested and compared with existing data
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