Thermal conductivity of foundation soil in permafrost area along China-Russia Crude Oil Pipeline and frost damage prevention and control

For China-Russia Crude Oil Pipeline passes through the permafrost area, serious pipeline deformation is resulted from the thaw settlement of frozen soil along the line due to the different thermal conductivity of the trench soil. Herein, the thermal conductivity of five typical foundation soils (gravelly sand, silt, silty clay, clay and peaty soil) along the pipeline was tested to master the variation laws of thermal conductivity with influencing factors. Definitely, the thermal conductivity of the 5 types of foundation soil was determined, the relationship of thermal conductivity with water content and dry density was analyzed, and thereby the regression equations were established. Then, the variation laws of thermal conductivity with mud content, plasticity index and loss on ignition were analyzed according to different soil conditions. In addition, the correlation degree of each influencing factor to the thermal conductivity of each type of foundation soil was calculated with the grey correlation analysis model. The results indicate that: the thermal conductivity of the 5 types of foundation soil varies with the change of water content and dry density, and the thermal conductivity of soils is very greatly affected by the soil conditions, but it is differently influenced by each factor. Hence, different prevention and control measures against frost damage were proposed for different types of foundation soil, so that reference could be provided to the frost damage prevention and control of the oil and gas pipelines in service or to be constructed in the permafrost area.