隧道大变形机制及处治关键技术模型试验研究

大变形是隧道建设中无法完全避免的灾害之一，发生后若处治不当极有可能出现多次换拱甚至塌方等二次灾害。通过相似模型试验，采用自行设计的隧道模型开挖装置和围岩内部位移监测装置，研究了隧道开挖和埋深增大过程中围岩渐进性破坏过程及位移和应力变化规律，揭露出预防隧道大变形的重点支护部位，并进一步研究了大变形出现后处治过程中衬砌的破坏规律，明确了大变形处治时的支护措施。试验结果表明：（1）隧道产生大变形过程中，拱顶与拱底的变形量大于拱腰与拱脚的变形量，且随着埋深增大，差值逐渐增大；（2）大变形产生后隧道拱顶径向和切向应力值均减小，而拱脚切向应力值大幅上升；（3）更换变形拱架时，更换位置附近衬砌拱顶处可能出现张拉破坏，拱腰处可能出现剪切破坏，因此，大变形处治时需保留两侧衬砌的临时钢支撑，必要时需增设底部横支撑或临时仰拱。该研究结果有助于得到大变形发生时和发生后处治时的防控重点，为大变形的预防及安全处治提供指导和参考。

Physical model test on large deformation mechanism and key treatment techniques of tunnel

The large deformation is one of tunnel disasters that cannot be completely avoided. When the tunnel is not properly treated after large deformation, it is likely to cause secondary disasters such as arches multiple replacement or tunnel collapses. With the self-designed excavation device and the internal displacement-measuring device for surrounding rock, a physical model test system was used to investigate the tunnel progressive failure, deformation and stress variation during tunnel excavation and buried depth increasing, thus revealing the key supporting parts to prevent large deformation of tunnels. Furthermore, the failure characteristics of the primary lining during large deformation treatment was also studied, and the supporting measures for large deformation treatment were defined. The results are summarised as follows. During the large deformation of the tunnel, the deformation of the vault and the arch bottom are larger than that of the arch waist and arch foot, and the difference increases gradually with the increase of buried depth. The radial and tangential stresses of the vault of tunnel decrease during the large deformation, while the tangential stress of the arch foot increases sharply. When the deformed arch frame is replaced, there may be tension failure at the lining arch near the replacement position, and shear failure at the lining arch waist. Therefore, it is necessary to retain the temporary steel support when the large deformation is observed, and the bottom horizontal support or the temporary inverted arch should be added. This study is helpful to obtain the key prevention and control location during and after the large deformation, which provides guidance and reference for the prevention and safe treatment of large deformation.