针对辽东湾某油田大管径双层保温管道，在不停产、不减产的情况下，对跨越航道的悬跨进行处理，并使管道下沉。完工后调查显示结果超预期，在不停产情况下实现了海管下沉4.5 m的最大深度。海管下沉至设计深度后的抛石保护设计采用原状土回填底层，既能节省成本又能提高施工效率。项目设计及施工中所采用的分析方法、分段挖沟下沉程序设置等技术可为今后类似工程项目的实施提供借鉴。

For a large-diameter double-insulating submarine pipeline located in Liaodong Bay, a span across channels is treated and subsidence protection is achieved during on-stream maintenance. Test results after the construction show that the subsidence depth reaches 4.5 m, which is the largest depth compared with other projects in China. In the subsequent rock dumping protection, trench soil is used to finish the first backfill layer, which can save the cost and greatly promote the construction efficiency. The design and construction methods used in this project are of value for further design of similar submarine pipeline projects.