以沈家门海中洲隧道为例，通过对隧道改建方案进行详细比选，在结构设计、原隧道塌方地段处理方案、开挖方案及监控量测中采取相应的技术措施，顺利完成隧道改建。得出以下结论： 1）针对海中洲隧道实际情况，改建方案采用扩洞方案更具优势； 2）设计采用比一般隧道适当加强的结构支护参数及地表注浆锚杆加固、塌腔处理、塌腔回填等塌方综合整治措施，对条件复杂的海中洲隧道是适用的； 3）对于扩挖的隧道，应在老衬砌的掩护下进行开挖及支护，保持初期支护紧跟，并尽快实现封闭成环，施工中应加强监测，保证施工安全。

Two rehabilitation options for Haizhongzhou tunnel are described and proper option is selected. Countermeasures are taken in tunnel collapse treatment, excavation and monitoring. Conclusions drawn are as follows: 1) Crosssection enlarging option is the proper option for the rehabilitation of Haizhongzhou tunnel. 2) Strengthened support parameters, ground reinforcement by grouted rock bolts installed from the ground surface, collapse treatment and backfilling are suitable for the rehabilitation of the tunnel. 3) The enlarging excavation should be executed under the protection of the existing lining, and the temporary support should follow the excavation immediately and should be closed to form a ring as soon as possible. Monitoring should be strengthened during the rehabilitation so as to guarantee the safety.