砾石地层冻土热物理特性研究

A study of the thermal physical properties of frozen soil in gravel layers

地铁建设中时有穿越富含砾石的地层,需使用冻结法施工,而砾石地层的热物理性质是冻结法设计的重要依据。为研究人工冻结砾石土热物理特性,通过自制试验仪器,开展了砾石土冻结温度、导热系数和容积热容量测定方法及其特性研究,并与黏土、粉土等典型土层进行对比分析。结果表明:砾石土冻结温度曲线变化符合常规变化规律,且冻结温度为-0. 21℃,高于黏土、粉土等;砾石土容积热容量与黏土、粉土等相近,随颗粒粒径增大,常温和冻结状态下土体容积热容量比值减小,其中砾石土的比值为1. 19;砾石土导热系数较大,冻结状态下达3. 89 W/(m·k),是常温状态下的1. 65倍,符合颗粒粒径对导热系数的影响规律。砾石土导热系数可按各组成物质的导热系数及其相应的体积比推算。

Artificial freezing method is widely used in metro construction which goes through some gravel sections. The physical properties of gravel layers are the key basis for the design of the freezing method, and resealvhes on themlal physical properties of artificial frozen gravel layers are lacking. To examine the themlal physical properties of artificial frozen gravel layers, a study of the freezing temperature, thermal conductivity and volumetric heat capacity of gravel layers was carried out with instrument developed at home. The physical properties of gravel layers were compared with those of clay, silt, etc. The results indicate that the freezing temperature change of gravel is in line with the typical change role and the freezing temperature of gravel is - 0.21 ℃, which is higher than that of clay and silt. The volumetric heat capacity of gravel is close to that of other soils. The ratio of volumetric heat capacity reduces with the increasing particle size in two situations （freezing and room temperature）. The ratio of volumetric heat capacity of gravel is 1.19. The themml conductivity of gravel is more than that of other soils titled in this paper. The thermal conductivity of gravel is 3.89 W/（m·k） in the freezing situation, which is 1.65 times the room temperature. The themml conductivity of gravel is in line with the role that a bigger particle size causes a bigger themml conductivity and can be calculated by the themlal conductivity of materials.