The Effects Of The Shield Tunneling On The Existing Underground Pipelines

With the booming of economy, an increasing number of cities begin constructing metro tunnel. The construction of shield tunnel generates soil disturbance, which may have influence on the urban underground structures and pipelines. Many of the existing underground pipelines have been a long time with low strength. Little disturbance will cause pipeline damage, leakage, or even lead to disasters. In this work, research was carried out based on the Hangzhou metro shield tunnel. The construction of this tunnel beneath the sewage pipelines, which have large diameter with water pressure. The project studied in this treatise is relatively rare in China in terms of sewer pipes, the number of sewers, spacing between shield and sewers and the crossing times.In this work, a numerical model is established to analyze the construction of metro across the sewage pipelines, taking the interactions between tunnel, pipelines and soil into consideration. The stress of pipelines, settlement of pipelines and internal stress of pipeline are calculated. And the finite element results are compared with measured results to verify the reliability of numerical results.Through the parameters analysis of the vertical distances between tunnel and pipelines, the pipeline materials and soil loss during construction, it showes that the soil loss has the greatest influence on the pipeline settlement while the vertical distances and pipeline materials have little effects. Therefore, the particular attention should be paid to the controlling of shield excavation to reduce the soil loss during construction process, and strengthening measurement on the pipeline is also recommended to reduce the impact of tunnel construction on existing pipelines.The technology of controlling earth pressure on the excavation surface, the technology of controlling shield advancing, the technology of simultaneous grouting control, the technology of secondary grouting, the technology of reinforcement of pipeline active area and the technology of monitoring pipeline during construction are summarized to guide other projects.