Research On The Thermal Character Of Undisturbed Permafrost Sample

With the development of the national economy,energy demanding is increasingly urgent,road and rail transport have been unable to meet such a request,and the construction of pipelines to solve this problem is the most convenient and quickest way. So the state decide to build the Sino-Russian oil pipeline.The pipeline cross the whole Da xing'anling perenially frozen soil regions structures building change the exchange between the thermal conditions and water transport processes.The surface conditions of heat exchange cause heat accumulation in the Subgrade and temperature increasing,which lead to thaw collapsibility. At the same time,due to the freezing of water in the process of migration and the volume of water in situ freezing expansion, the formation of frost heave is inevitable,soit makes structure frost heaving disease. Therefore for engineering structures,analysis of the interaction between environment and permafrost is of great significance to ensure stability of the buildings.This requires a detailed analysis to frost temperature field. we need to know the thermodynamic parameters in order to analy the frost temerature change.Basing on the Sino-Russian oil pipeline project,through laboratory test,specific heat and coefficient of thermometric conductivity of the original soil are measured. Furthermore some parameterssuch as volumetric specific heat,coefficient of thermal conductivity are obtained.Using summarize,classify,contrast and other analytical methods, it studies the factors and the general laws to these parameter and compares them with the previous results. The paper is divided into five parts.In the first part it introduces some lessons on construction of pipelines in the frost zone and research status of some physical parametres such as aggregate specific heat,volumetric specific heat, coefficient of thermometric conductivity coefficient of thermal conductivity. In the second part it analyze the coefficient of thermometric conductivity of the original soil.At first it introduces the concept of coefficient of thermometric conductivity and the test principal,then makes an explain of the test instrument and the test data.Secondly it analyze the factors and the general law to coefficient of thermometric conductivity of the different soil.The result is that coefficient of thermometric conductivity has a better linear relationship with water content and dry density.It increases with water content increasing while decreases with dry density increasing.Finally, the test data is compared with the code data .The former are bigger than the latter.In the conditon of the same water content the difference between them is more obvious with the grain diameter increasing,but in the condition of high water content the code result is much bigger than the test results.In the third part of the paper it instroduces the concept of aggregate specific heat and volumetric specific heat and their test prnicipal,instruments,test steps and basic formula of volumetric specific heat.What's more it analyze the test result carfully.Firstly,the test data are compared with the code datat by mathematical statistical methods.The result is there has little difference to the reference.Both of them can be used as aggregate specific heat of xin'anling frost region.At last the reference values are provided as the aggregate specific heat of different soil.The general law is that the aggregate specific heat is increasing with the grain diameter decreasing while the aggregate specific heat is increasing with organic content increaing.Secondly,it get the law of caculating volumetric specific heat through specific heat.Finally,comparing the result of volummetric specific heat through caculation with the result of stimulation test,in condition of the same water content volummetric specific heat of fine-grained soil is bigger than the reference,while volummetric specific heat of gravelly sand including fine-grained soil is bigger than stimulation results.In the forth part it analyze the influencing factors of the coefficient of thermal conductivity and compare them with standardized reference value.At first it provide the formula to the coefficient of thermal conductivity through according to coefficient of thermometric conductivity and volumetric specific heat.Secondly,through analysis of the whole coefficient of thermal conductivity data,it provide the reference for Da xing'anling perpetually frozen soil.Finally comparing the test data with the references in the norms,in condition of the same water content the result of the original soil is smaller than the laboratory simulation result,while even much small when at the high water content.At the last part ,through the analysis of the four parts above,it provides us with the general law of the thermal physical parametres and the differences of the laboratory simulation data .Furthermore it provides the reference value for the future projects.