强震区浅埋偏压隧道洞口段减震层减震效果分析

Analysis on the Seismic Response Reduction of Shock Absorption Layer in the Shallow and Unsymmetrical Pressure Section of Tunnel Portal in Strong Earthquake Area

依托某铁路隧道洞口段,利用FLAC3D软件研究隧道施设不同厚度减震层的减震效果。结果表明:(1)与不设减震层相比,施设5 cm减震层后,二衬结构最大、最小主应力分别减小了26.05%、21.57%,竖向、纵向位移分别减小了74.68%、36.13%,竖向位移差减小了0.32 mm,最小安全系数平均提高了50.46%;(2)施设10 cm减震层后,二衬结构最大主应力增大了134.45%,最小主应力减小了26.70%,竖向、纵向位移分别减小了70.80%、26.89%,竖向位移差增大了1.85 mm,最小安全系数平均提高了11.10%;(3)施设15 cm减震层后,二衬结构最大、最小主应力分别减小了45.38%、25.16%,竖向、纵向位移分别减小了70.89%、13.45%,竖向位移差增大了1.89 mm,最小安全系数平均提高了12.56%;(4)衬砌与围岩之间施设5 cm减震效果优于施设10 cm、15 cm减震层的减震效果。研究成果可为隧道洞口浅埋偏压段减震技术的发展提供参考。

Based on a railway tunnel portal section,this study utilizes FLAC3D to analyze the damping effect of different thicknesses of damping layers applied between the liner and the surrounding rock.The results show that:(1)Compared with no seismic damping layer,after applying a 5 cm damping layer,the maximum and minimum principal stresses of the secondary lining structure are reduced by 26.05%and 21.57%,the vertical and longitudinal displacements are reduced by 74.68%and 36.13%,the vertical displacement difference is reduced by 0.32 mm,and the minimum safety factor is increased by 50.46%on average.(2)After applying a 10 cm damping layer,the maximum principal stress of the secondary lining structure increases by 134.45%,the minimum principal stress decreases by 26.70%,the vertical and longitudinal displacements decrease by 70.80%and 26.89%,the vertical displacement difference increases by 1.85 mm,and the minimum safety factor increases by 11.10%on average.(3)After applying 15 cm damping layer,the maximum and minimum principal stresses of the secondary lining structure decrease by 45.38%and 25.16%respectively,vertical and longitudinal displacements were reduced by 70.89%and 13.45%respectively,vertical displacement difference increased by 1.89 mm,and minimum safety factor increases by 12.56%on average.(4)The seismic damping effect of applying 5 cm between the liner and the surrounding rock is better than that of 10 cm and 15 cm damping layers.The results can be used as a reference for the development of shock absorption technology in shallow tunnel portal.