| The rapid industrialization of China has caused a large consumption of oil andgas resources,China-Russia oil pipeline project play an important role to guarantee theprovision of oil and gas resources for our country.But the pipeling through about965km2frozen area in Da Hinggan Mountains and Nen River Valley,The underlyingsoil temperature rise and the permafrost has a negative impact to the security andstability of the pipeline because of heat transferthe and heat accumulation caused byoil temperature of the pipe and climate change. The study of melting permafrostfocuses on the thermal field and heat transfer.The double-track projection ofChina-Russia oil pipeline is planning to construct in2014,the frozen oil laboratory ofConstruction&Engineering College of Jilin University has deeply researched onthermal properties of the permafrost in the pipe area.The thermal conductivity is a vital basic indicators in parameters ofthermodynamic，It is has a significant impact to the temperature change of frozen soiland the transfer of heat.The frozen oil laboratory of Construction&EngineeringCollege of Jilin University has used the Heat-flow meter method,the Hotline methodand Formal-state method to test the specific heat&heat diffusivity&thermalconductivity of hundreds of frozen soil specimen of China-Russia Oil Pipeline in2007,and achieved fruitful research result.Comparative method is one of Steady-statemethods to test the thermal conductivity,in order to enrich the thermal conductivitytested method and find a method to acquired a thermal conductivity which is closer tothe value of undisturbed soil by laboratory test.In the first part,a comparative methodtesting instrument was autonomos maked according to the principle and the idea ofcomparative testing of thermal conductivity,solved a number of technical difficultiesin the making process and achieved some advantages,for example,ensure one-wayheat flow,rarely thermal diffusion and more controllable.In the second part,the thermal conductivity of2#silty clay came from the area of China-Russia oil pipeline was experimented by comparative method,and the resultshave been contrastively analyzed with test results of the relevant specification,Heat-flow meter method and Hot-wire method and found that the results ofcomparative method and the Heat-flow meter method was closest to Formal-statemethod test results,which was a test with undisturbed soil specimen of2#silty clay. Itmeant that the test results of comparative study and Heat-flow meter method werecloser to the thermal conductivity of undisturbed soil.In the third part,5typical soils (1#silty clay,2#silty clay,3#flourysoil,4#sandysoil,5#gravelly soil) take from permafrost area of China-Russia oil pipeline wasexperimented by comparative method to get thermal conductivity value, the linearregression model of thermal conductivity of5kinds of soil and its influence factorswas obtained by SPSS,which is a mathematical statistics analysis software.then thechange rule between thermal conductivity and above-mentioned influence factors wasdiscussed from four aspects,including dry density,water content, freeze-thawcondition,and soil conditions.The study shows that the result of comparative method is closer to undisturbedsoil thermal conductivity.The thermal conductivity of four typical of Da HingganMountains permafrost are positively correlated with soil dry density and water content,and has a good relationship with the fitting curve. Almost all frozen soil has strongerheat-conducting property than melted soil.In the same condition,the descending orderof the thermal conductivity is sandy soil,floury soil,silty clay, which meets the orderof size of soil particles.The5#gravelly soil has no features of soil mentioned abovebecause of uneven size of soil particles.The study provides a reference for thermal conductivity test method selectingand have a great significance for maintaining the structural integrity and stability ofthe pipeline and other construction in permafrost area. |
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