针对王岗山隧道出口段三线车站隧道断面施工前期CRD与台阶法施工存在拱顶下沉与收敛变形过快过大，断面拱顶下沉和收敛变形速度达到3~5 mm/d，日最大下沉和收敛值为4.7 mm和4.8 mm，15 d内累计下沉109 mm、收敛53 mm，且下沉、变形还在进一步发展中，存在围岩侵入设计限界的问题，通过现场调研，分析大变形产生的主要原因在于埋深浅、跨度大、扁平率低、穿越辉绿岩侵入岩与沉积岩的混杂带，岩体破碎，岩质软弱、易滑。提出优化施工方案，采用双侧壁导坑法施工，优化超前和初期支护措施，并制定详细的施工步骤。实际监测结果显示，该优化施工方案有效地控制了围岩变形，初期支护达到了较好的效果，收敛和拱顶下沉基本未突破预留值，保证了施工安全，为按时完成隧道施工提供了保障。

The crown top settlement and convergence deformation of trilane tunnel at Wanggangshan Tunnel Portal are fast and large by CRD method and bench method; the crown top settlement and convergence deformation rate reaches 35 mm/d, the daily maximum settlement and convergence reach 4.7 mm and 4.8 mm, respectively; the 15day accumulated settlement and convergence reach 109 mm and 53 mm, respectively; and the deformation is still developing. Hence, site investigation is carried out. The analytical results show that the main causes for large deformation are shallow burry, large span, low flattening rate and mixed zone of diabase intrusive rock and sedimentary rock which is broken weak and slippery. The optimization of the construction scheme is put forward, including using doubleside drift method, advanced support and primary support optimization and detailed construction sequence. The monitoring results show that the deformation of the surrounding rock has been effectively controlled, good primary support effect has been achieved, the crown top settlement and convergence have been effectively controlled, and the tunnel safety has been guaranteed.