【摘要】 软弱围岩由于强度低、稳定性差、变形持续时间长等特点,在隧道施工中常引起大变形、崩塌等破坏现象,导致初支结构强烈变形甚至破坏,严重影响隧道施工和安全,是隧道建设中遇到的主要难题之一。通过对贵阳—广州铁路天平山隧道试验段锚杆轴力、围岩压力及钢架应力的监测,分析各支护构件的受力特征。研究结果表明:对于初期变形速率较大的软弱围岩,锚杆轴力多呈中间大、两端小的分布型式,且轴力变化历时长,不易稳定;在同等地质软弱围岩条件下,型钢钢架的围岩压力比格栅钢架增大70%～90%,型钢钢架的应力分布较均匀,支护效果要优于格栅钢架。更多还原

【Abstract】 The failure phenomena such as large deformation and collapse usually occur in weak surrounding rock of tunnels after excavation because of low strength,poor stability and long deformation period.The failure phenomena result in intense deformation and damage of the first stage support,which have a strong impact on construction and security of tunnels and become a major problem in the construction of tunnels.Mechanical characteristics of the support system are analyzed by monitoring axial force of rock bolts,pressure of surrounding rock and stress in the steel frames for Tianpingshan tunnel of Guizhou—Guangzhou Railway.It is concluded that,for the weak surrounding rock which has large deformation rate in the first stage of excavation,the axial force of rock bolts is often large in the middle and small in the ends;and its variation often lasts for a long period of time.The profile steel frame has larger surrounding rock pressure than the grid steel frame by 70%–90% under the same geologic conditions;the profile steel frame has more uniform stress distribution and better support effect than the grid steel frame.更多还原