Safety evaluation method for parallel construction of new and in-service pipelines

In the case that a new pipeline is constructed in parallel to an in-service pipeline, the construction method of steel sheet pile support and soil accumulation above the in-service pipelines is required for the excavation of new pipeline trenches due to the limited construction space in some areas. In order to ensure the ontological safety of in-service pipelines and the support safety of new pipelines in such cases, a method was proposed to check the radial stability and girth weld stress of in-service pipelines. Meanwhile, a calculation method was also developed for the stress of support structure, stability, displacement and cross-section strength of new pipelines.Hereby, the safety of new Tangshan LNG Pipeline and the in-service pipelines Ⅰ and Ⅱ was checked with the above methods. The excavation depth of the new Tangshan LNG Pipeline was 3 m with 9 m steel sheet piles supported the pipe trench, and the height of soil piles above the in-service pipelines Ⅰ and Ⅱ on both sides were not more than 2 m. In such case, the ontological safety of the in-service pipelines Ⅰ and Ⅱ as well as the support safety of the new pipeline could meet the safety requirements. Generally, this method could provide rererence to determine the safety of parallel construction during pipe sinking under similar conditions of limited construction space.