成兰铁路跃龙门隧道深埋越岭段大变形原因分析研究

Analysis on Causes of Large Deformation in the Deep-buried Mountain Ridge Section of Yuelongmen Tunnel on Chengdu-Lanzhou Railway

成兰铁路跃龙门隧道在深埋越岭段中间平导发生严重大变形,采取有效支护措施后变形趋于稳定。在对应平导变形段落左线开挖贯通后,平导及左线再次发生严重变形。基于此,文章系统介绍了隧道区域地质环境、区域地应力、施工中围岩变形特征以及现场施工大变形的判定过程,分析表明,该段大变形是在高地应力环境下岩体软弱破碎引起的,在此特殊地质环境中群洞效应显著,且大变形和岩层走向与洞轴线夹角、地应力最大水平主应力方向与洞轴线夹角有较大关系,并通过回填中部平导,新增较大线间距的外侧平导,增加洞室间距来解决大变形问题。

The middle parallel pilot tunnel of the Yuelongmen Tunnel on the Chengdu-Lanzhou Railway encountered severe deformation in the deep-buried mountain ridge section.After effective support measures were taken,the deformation tended to be stabilized.After excavation and breakthrough of the left line main tunnel in the corresponding deformation section of the pilot tunnel,severe deformation occurred again in the pilot tunnel and the left line main tunnel.On this basis,this paper systematically introduces the geological environment of the tunnel site area,regional geostress condition,deformation characteristics of surrounding rock during construction,and the process of identifying large deformation in site construction.The analysis shows that the large deformation in this section is caused by the weak and broken rock mass in the high geostress environment.In this special geological environment,the tunnel group effect is significant,and the large deformation is closely related to the included angle between the rock strata strike and the tunnel axis,and the included angle between the maximum horizontal principal stress direction of the geostress and the tunnel axis.The problem of large deformation is solved by backfilling the middle pilot tunnel,constructing a new outside pilot tunnel with a larger spacing between pilot tunnel and main tunnel.