Research on mechanism of insulation effect and thickness influencing factors of tunnel anti-freezing insulation layer in cold regions
21 calculation working conditions were set for the highway tunnel in cold regions with anti-freezing insulation layer laid at the lining surface.By conducting numerical simulation calculations on the radial temperature field of tunnel anti-freezing insulation layer,lining,and surrounding rock under annual cycle,as well as the required thickness of the anti-freezing insulation layer for each working condition,the mechanism of insulation effect of the tunnel anti-freezing insulation layer and influencing factors on the required thickness were studied.The results show that the insulation effect of the anti-freezing insulation layer is significant,which mainly reflects in reducing the annual temperature amplitude of the tunnel lining and surrounding rock,meanwhile the annual average temperature also increases to a certain extent.As the thickness of the anti-freezing insulation layer increases,the annual average temperature and temperature amplitude of the tunnel lining and surrounding rock increase and decrease exponentially,respectively,and the corresponding annual minimum temperature also increases exponentially.The thicker the anti-freezing insulation layer,the better the insulation effect,but the insulation efficiency continues to decrease.The larger the thermal conductivity coefficient,and the lower the thermal conductivity coefficient of the surrounding rock,the more significant the insulation effect of the anti-freezing insulation layer.The required thickness of the anti-freezing insulation layer decreases exponentially with the increase of the thermal conductivity coefficient and initial temperature of the surrounding rock,increases logarithmically with the increase of the thermal conductivity coefficient of the surrounding rock,and linearly decreases and increases with the increase of the annual average temperature and annual temperature amplitude,respectively.The thickness of the anti-freezing insulation layer should be calculated and determined by considering all the above factors comprehensively.
tunnel engineeringcold regionanti-freezing insulation layermechanism of insula-tion effectinfluencing factor
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