【摘要】 西部地区普遍出露层片状岩体。由于强度低、自稳能力差、结构强度呈现各向异性等特点,在隧道开挖过程中常引起围岩大变形,导致初期支护结构强烈变形失稳而不得不频繁进行拆换。部分洞段二次衬砌混凝土甚至发生劈裂、掉块的破坏现象,严重影响隧道施工的进度与安全。以兰渝铁路两水隧道为工程背景,采用现场实时监测、数值模拟等手段,获取大断面隧道围岩与支护系统之间的接触压力,揭示开挖断面不同位置接触压力随时间发展规律和空间分布特征。研究结果显示,受围岩结构强度的各向异性控制,隧道开挖后支护受力极不均匀。空间上与围岩变形集中部位一致,时间上变化历时长,且由于开挖方式的影响不易稳定。初期支护钢拱架局部荷载过大而发生侧向扭曲失稳,且监测的失稳发生时间与收敛形变稳定时间相比而明显滞后。根据层状围岩的支护受力特征,提出针对此类岩体更为合理的隧道设计建议。更多还原

【Abstract】 The layered soft rock is widely distributed in Western China, such as slate, carbonaceous slate, phyllite, and so forth.During the tunnel excavation, geotechnical problems frequently occur in the surrounding rock, such as excessive overbreak and intense deformation associated with asymmetric squeezing, because of low strength, poor self-stability and intense anisotropy of structural strength in layered surrounding rock. Large deformation can result in intense damage to the primary support, and even splitting of secondary support, significantly influencing the construction and security of tunnels. At the site of Liangshui tunnel in Lanzhou-Chongqing railway, a series of real-time contact pressure monitoring tests is conducted at different positions in section between surrounding rock and support system. Mechanical responses of the support system are analyzed in time and spatial domains using the monitored contact pressure. In-situ monitoring and numerical inversion analyses of displacement are also performed. The results indicate that the contact pressure of support system shows irregular distribution in space, which agrees with the concentrated deformation position of the surrounding rock; and its variation often lasts for a long period of time due to the influence of excavation method. The failure of the steel arch frame takes place in the weak axis plane because of its smaller lateral anti-bending rigidity.Meanwhile, the monitoring data show that their occurrence significantly lags behind the stabilization of convergence deformation.Based on the force characteristics of the support system, a more reasonable design scheme is proposed for tunneling in such a kind of rock.更多还原