Laboratory Investigation On Thermal Conductivity Of Typical Soil In Northeast Inner Mongolia During Freezing And Thawing Process

The thermal stability of foundation and geotechnical structure in cold region is influenced by the external thermal environment and the thermal characteristics of the soil.In the calculation,analysis and prediction of the civil engineering thermal stability in the cold region,the parameter of thermal conductivity is an important calculation parameter.In the actual civil engineering of cold region,the soil as the foundation or structure will undergo various freezing thawing processes and freeze-thaw states.Therefore,it is of great significance to accurately grasp the evolution of the thermal conductivity of the soil in different freeze-thaw processes and freeze-thaw conditions and its influencing factors,which is of great significance to the thermal calculation and the thermal stability and control of the cold region civil engineering.Therefore,this paper selected three kinds of typical typical soil in the northeast of Inner Mongolia,and studied the change law of this three kinds of soil under the conditions of different dry density,water content and temperature by using the thermal probe method in the unsteady state method.The main conclusions are as follows:(1)the thermal conductivity of the soil can only be carried out at a certain temperature,and it can not be tested under the condition of constant temperature change.This paper improves the test system and realizes continuous dynamic testing of thermal conductivity under variable temperature.The improved test system is stable and reliable,achieving three kinds of continuous dynamic testing of soil thermal conductivity.(2)when the soil quality is different,the thermal conductivity of the soil is significantly different due to the mineral composition of the soil.When the dry density is 1.7g/cm~3 and the water content is 10%,the thermal conductivity of Tongliao silt at-10?is 2.487W/(m?K),and the thermal conductivity of the Tongliao silt at 10?is 2.207W/(m?K).The 0.609W/(m?K)and0.634W/(m?K)of Tongliao organic soil were significantly higher than those under the same conditions,0.858W/(m?K)and 0.83W/(m?K)of Genhe peat soil.(3)in the same soil,when the dry density of Tongliao organic soil increased from 1.3g/cm~3 to1.7g/cm~3,the thermal conductivity of the positive temperature region increased from 0.432W/(m?K)to 0.634W/(m?K),and the thermal conductivity of the negative temperature region increased from 0.415W/(m?K)to 0.609W/(m?K),while the water content of organic soil under the dry density condition was water content.From 0%to 25%,the thermal conductivity in the positive temperature region increased from 0.306W/(m?K)to 1.551W/(m?K),and the thermal conductivity in negative temperature increased from 0.302W/(m?K)to 2.09W/(m?K).Genhe peat soil has the similar rule.The effect of dry density on thermal conductivity is lower than that of moisture content on thermal conductivity.(4)when the dry density and water content are certain,the equivalent temperature of the thermal conductivity can be obtained by analyzing the influence of temperature on the thermal conductivity of the three kinds of soil.When the dry density is 1.7g/cm~3 and the water content is10%,the temperature zone is measured at 12.5?in the positive temperature zone,and the thermal conductivity of the soil at-15?is measured at the negative temperature zone.It can reduce the number of times and shorten the test period when using this equivalent temperature on the premise that it can meet the accuracy requirements.(5)After comparing the calculated values of the theoretical calculation models and the measured values of the thermal conductivity of this paper,it is found that the prediction accuracy of the Kerstem model is the worst and can not meet the actual engineering requirements;the Johansen model has little difference with the C-K model(C?téand Konrad model).However,the C-K model is more suitable for the theoretical model of soil thermal conductivity in the northeast of Inner Mongolia in consideration of the soil type factor and particle shape parameters is introduced which can makes it more widely applicable.