为加强对超大断面隧道加宽段围岩变形和围岩压力变化规律的认识并总结工程经验，依托厦门海沧疏港通道蔡尖尾山2#隧道，对不同加宽段通过优化工法、增加步序及尽早闭环等措施控制围岩变形，并对开挖过程中的不同加宽段围岩变形、围岩压力及支护轴力进行现场监测和对比分析。结果表明： 1）超大断面隧道中,随跨度的增大围岩变形总量增大，围岩变形趋近于平稳的时间也愈久，变形速率不随施工工法的变化而改变； 2）拱顶附近围岩的周边收敛大于拱腰处围岩的，且二者的收敛总量差值随着开挖跨度的增加而增大，超大断面隧道施工中应重点关注拱顶处的围岩变形； 3）在两隧道中夹岩处围岩会产生偏压，建议多关注中夹岩侧的应力监测； 4）分析结果证明该超大断面隧道工法优化可以控制围岩变形。
To learn the deformation and pressure variations of
surrounding rock in the widened sections of super-large
tunnel, the Caijianweishan #2 tunnel in Xiamen is studied as a typical example.
In different widened sections of the tunnel, various deformation control
measures, like optimizing construction method, increasing step sequence, and
closing the loop as early as possible are taken, and on-site monitoring and comparative analysis for deformation,
surrounding rock pressure, and supporting axial force are carried out. The
results show that: (1) In tunnels with super-large
cross-section, the total amount and duration of
surrounding rock deformation increase with span, but its deformation rate does
not change with construction method. (2) The peripheral convergence of
surrounding rock near the vault is larger than that at the arch waist, and the
total amount difference of their convergence increases with the excavation
span, thus the deformation of surrounding rock at the vault should be focused
on in construction. (3) As deviatoric pressure is produced at the vault in the
middle of two tunnels, more attention should be paid to the stress monitoring
of the middle rock side. (4) The analysis results verify that the construction
method optimization is effective to control deformation in this super-large section tunnel.
