Shell versus beam representation of pipes in the evaluation of tunneling effects on pipelines

• Published in: Tunnelling and underground space technology Vol. 23; no. 4; pp. 431 - 437
• Main Authors: Klar, Assaf, Marshall, Alec M.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.07.2008; Elsevier
• Subjects: Applied sciences; Buildings. Public works; Computation methods. Tables. Charts; Exact sciences and technology; Pipelines; Structural analysis. Stresses; Tunneling; Tunnels, galleries; Tunneling; Pipelines; Buried construction; Buried pipe; Impact study; Modeling; Beam(mechanics); Pipeline; Existing installation; Shell; Formulation; Tunnel driving; Comparative study
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2007.07.003

The problem of tunneling effects on pipelines is approached in the paper. Previous solutions treated the pipeline as a simple Euler–Bernoulli beam. Strictly speaking, this treatment cannot be rigorous as the pipe itself is actually a three dimensional structure loaded all around. It is therefore possible that the Euler–Bernoulli beam representation is not suitable for all cases. The current paper examines this issue by comparing analysis results of soil-pipe-tunnel interaction based on two different formulations. In one formulation the pile is represented as a Euler–Bernoulli beam, while in the other it is treated as a three dimensional structure composed of shell elements. The soil behavior and the tunneling induced displacements are identical in the two formulations, thus any variation in behavior is solely a function of the employed pipe representation method. It is found that when the relative material stiffness of the pipe and soil is small, the pipeline does not behave as a beam, and the results of the two theories differ. As the relative pipe-soil material stiffness increases the two solutions approach each other and eventually coincide for large relative pipe-soil material stiffness values. It is shown that typical concrete and steel pipes can be well represented as simple beams, while polyethylene pipes may require the shell element representation for more accurate predictions.