3D numerical modelling of the impact of tunnelling in soft soil on buried pipelines

The underground space in urban areas is congested with structures, including pipelines, which are affected by underground construction such as tunneling. This paper investigates the problem of tunneling effects on buried pipelines, using finite difference code FLAC3D. A 3D numerical pipe-soil model is developed and tunneling effect is simulated with settlement troughs which are applied at the bottom of model. 2D and 3D settlement troughs are adopted respectively to study the pipeline behavior at the final state of tunneling and in the process of tunneling. A series of numerical parametric studies is performed to analyze various combinations of settlement profiles, joint stiffness, pipe material properties and soil properties. The results are summarized and presented in a normalized plot of relative joint-pipe stiffness, relative pipe-soil stiffness, joints spacing and relative position between joints and tunnel, which are validated with an analytical approach given by Klar et al. Effect of tunneling orientation relative to pipeline is also explored. The results indicate it might be un-conservative if the analysis only considers the final state of tunneling as the critical state but neglects the variation of stress in the process of tunneling.