强震区围岩局部缺陷对隧道衬砌受力影响分析

Effect of Local Defect of Surrounding Rock on Lining Stress of Tunnel in Meizoseismal Area

研究目的:已有震害调查表明,围岩施工塌方引起的局部缺陷段在地震作用下均出现了不同程度的二衬剥落、错台、整体垮塌等震害,而国内外隧道相关规范多关注洞口和断层的结构抗震问题,对围岩局部缺陷段关注甚少。因此有必要深入探讨围岩局部缺陷条件下隧道结构震害特征及参数敏感性,以期为强震区围岩缺陷段设计及施工处置提供理论参考。研究结论:(1)围岩局部缺陷几何尺寸的增大不会改变动峰值加速度PGA、主应力、内力响应频谱变化规律,但会不同程度增大隧道衬砌主要部位PGA、主应力峰值和内力峰值大小;(2)局部缺陷位置变化(拱顶、拱肩、拱腰)具有显著的“局部区域特性”,但无论缺陷位于什么部位,拱肩、拱顶均为薄弱部位,实际工程应对相应位置抗减震措施设置予以重视;(3)围岩状态越差、埋深越浅,越不利于隧道衬砌结构抗震;(4)围岩局部缺陷影响因素(缺陷位置p、围岩级别s、隧道埋深h、环向角度θ、径向长度l、轴向长度b)对隧道衬砌结构动力响应影响敏感性强弱关系为:缺陷位置p>围岩级别s>轴向长度b>环向角度θ>径向长度l>埋深h。

Research purposes:The existing seismic damage investigation shows that the seismic damage of secondary lining spalling,staggered platform and overall collapse caused by surrounding rock local defect sections of construction collapse often occur under the earthquake action.However,the relevant codes of tunnels pay more attention to the structural aseismic of portal and faults,and little attention is paid to the local defective sections of surrounding rocks.It is necessary to study seismic damage characteristics and parameter sensitivity under the condition of local defect of surrounding rock,so as to provide a theoretical reference for design and construction.Research conclusions:(1)The increase of geometric size of local defects in surrounding rock will not change the law of PGA,principal stress and internal force response spectrum,but the value of above parameters will be increased in varying degrees.(2)The influence of local defect location change has significant local regional characteristics,but the arch shoulder and arch crown are weak parts no matter where the defect is located.So the anti-seismic measures should be taken seriously in corresponding parts of practical engineering.(3)The worse the state of surrounding rock and the shallower the buried depth,the worse the seismic resistance of lining structure.(4)The sensitivity of the influence factors of local defects(defect location p,surrounding rock grade s,tunnel burial depth h,circumferential angleθ,radial length l,axial length b)on the dynamic response of lining structure is as follows:p>s>b>θ>l>h.