层理面倾角对围岩蠕变及支护结构力学特性的影响研究

Influences of Bedding Planes Dip Angles on Creep Properties of Surrounding Rock and Mechanical Response of Tunnel Structure

汶马高速公路沿线广泛分布着以炭质千枚岩为代表的层状软岩,围岩蠕变特征和支护结构的力学响应受层理面倾角的影响显著。以鹧鸪山隧道为依托,利用块体离散元软件3DEC,建立了当层理面倾角β分别为0°,30°,60°和90°时,隧道的数值模型并进行计算,结合对断面长期监测数据的分析,主要得出以下结论:层状软岩隧道周边围岩的变形和结构受力具有显著的非对称特性,二次衬砌的安全系数较小,且收敛时间较长;二次衬砌内力受围岩蠕变效应的影响明显,轴力与弯矩的增长率在第1个10年内较大,随后增长率趋于稳定;随着层理面倾角的增加,最大正弯矩向左拱腰位置偏转,最大轴力向右拱腰位置偏转。层理面倾角越大,弯矩的增长率越小。

Layered soft rocks represented by carbonaceous phyllite are widely distributed along WenchuanMaerkang Highway.Creep effect and mechanical response of supporting structure are obviously affected by the dip angles of bedding planes.Based on Zhegu Mountain Tunnel,this paper establishes several numerical models,the dip angleβof which are respectively taken as 0°,30°,60°and 90°.The results indicate that the deformation and mechanical response of the tunnel shows a significant asymmetric property.The safety factor of secondary lining gradually declines for a long time.Creep effect has significant influence on the internal force of secondary lining.The growth rate of axial force and bending moment is relatively large in the first 10 years,then the rate becomes stable.With the increase of the dip angle,the maximum positive bending moment gradually deflects to the left haunch while the maximum axial force deflects to the right haunch.The growth rate of bending moment declines when the dip angle grows.