土壤热参数及其影响因素测试分析

Testing and analysis of soil thermal parameters and their influencing factors

热性质是岩土体基本的物理性质之一,用以评价热量在其中的保持、传导和分布状况,以导热系数、比热容和热扩散系数最为常见,这些参数也是地热能管理与开发、工程冷冻开挖、寒区工程设计与施工的重要参数。已有研究表明,土壤热参数与土质、来源、含水率、密度等因素有关。通过广东湛江某工地粉质黏土和黏土的热参数测试结果分析发现:随含水率的增大,粉质黏土导热系数和热扩散系数的变化趋势是先增加至最大值,然后减小,而比热容基本呈线性增大。干密度对粉质黏土导热系数的影响与含水率大小有关,当含水率不超过20.0%时,其随干密度的增加而增大,而当含水率超过27.5%后,其随干密度的增加有减小趋势;当含水率在24.5%(液限)左右时,基本没有规律可循。干密度对粉质黏土热扩散系数影响规律不明显。黏土的导热系数和比热容都随含水率和干密度的增加而增大;热扩散系数随含水率的升高整体表现为非线性增加至稳定,在低含水率下干密度的影响不明显,在较高含水率下随干密度的增加热扩散系数先增大后减小。较大颗粒的存在导致粉质黏土的导热性较黏土复杂。

Thermal property is one of the basic physical properties of rock and soil,and it is widely used to evaluate the retention,conduction and distribution of the heat.Thermal conductivity,specific heat capacity and thermal conductivity are the most common parameters,and they are also used in geothermal energy management and development,engineering freezing excavation and construction design in cold areas.The existing studies have shown that soil thermal parameters are associate to some factors such as the soil types,source,water content,density.In this study,the thermal parameters of silty clay and clay at a construction site in Zhanjiang,Guangdong province were tested.The results show that with increasing water contents,the thermal conductivity and thermal diffusivity of silty clay increase to a maximum value and then decrease,while the specific heat capacity increases linearly.The effect of dry density on thermal conductivity of silty clay depends on the moisture.When the water content is less than 20.0%,the thermal conductivity increases with the increase of dry density,while the water content is over 27.5%,it decreases with the increase of dry density.At the water content of about 24.5%(liquid limit),there is no law to follow.The effect of dry density on thermal diffusivity of silty clay is not obvious.Both the thermal conductivity and specific heat capacity of clay increase with the increase of water content and dry density.As the water content increases,the thermal diffusivity increases nonlinearly until it is stable.Under a low water content,the dry density does not significantly affect the thermal diffusivity;however the thermal diffusivity increases firstly and then decreases with increasing dry densities under the high water content.In addition,it is also found that the existence of large particles can cause the thermal conductivity of silty clay to be more complicated than that of clay.