冻融循环下寒区隧道衬砌结构性能劣化研究OA

To address the performance degradation and structural failure of high-latitude cold-region tunnels under freeze-thaw cycles,concrete freeze-thaw cycle tests were conducted to investigate the strength deterioration law of concrete under freeze-thaw cycles.A thermo-mechanical coupling numerical analysis model for tunnel lining in cold regions under variable temperature conditions was established to analyze the effects of site temperature,insulation layer thickness,and insulation layer layout method on the tunnel freeze-thaw zone,structural internal forces,and damage evolution.The results showed that:(1)as the number of freeze-thaw cycles increased,the elastic modulus and peak stress of concrete decreased,while the peak strain increased.A full-process compressive stress-strain constitutive relationship of concrete considering the number of freeze-thaw cycles was further proposed.(2)The smaller the temperature amplitude at the tunnel site and the thicker the insulation layer,the lower the temperature change rate of the surrounding rock and the smaller the freeze-thaw distribution range.The wall-attached insulation layout produced the smallest freeze-thaw range and the best insulation effect.(3)Overall frost heave of the surrounding rock generated additional stresses in the lining structure.After overall frost heave,the locations of the maximum tensile and compressive stresses in the lining structure remained unchanged,occurring at the free face of the inverted arch and the arch foot,respectively.(4)Damage in cold-region tunnels was mainly concentrated in the inverted arch area,and the early damage level was relatively low.With increasing service years,the damaged area expanded continuously and formed through-cracks,leading to inverted arch failure.(5)A smaller temperature amplitude at the tunnel site and a greater insulation layer thickness delayed the damage initiation of the lining structure and increased its service life.The wall-attached insulation layout fully achieved the insulation effect,and no frost-heave damage occurred when the thickness reached 4 cm.