EFFECT OF SOIL RESTRAINT ON THE BUCKLING RESPONSE OF BURIED PIPELINES

Long-term large deformation geohazards can impose excessive deformation on a buried pipeline. The ground displacement field may initiate pipeline deformation mechanisms that exceed design acceptance criteria with respect to serviceability requirements or ultimate limit states. Conventional engineering practice to define the peak moment or compressive strain limits for buried pipelines has been based on the pipeline mechanical response for in-air conditions. This methodology may be conservative as it ignores the soil effect that imposes geotechnical loads and restraint on buried pipelines. The importance of pipeline/soil interaction and load transfer mechanisms that may affect local buckling of buried pipelines is not well understood. The authors previously developed a new criterion for local buckling strain of buried pipelines in stiff clay through response surface methodology (RSM) [1, 2]. In this paper the new criterion was compared with a number of available in-air based criteria to study the effect of soil restraint on local buckling response of buried pipelines. This criterion predicted larger critical strain than selected in-air based criteria which shows the significant influence of soil presence. The supportive soil effect is discussed. The soil restraining effect increases the pipeline bending resistance, when the pipeline is subjected to large displacement-controlled ground deformation. A correlation between Palmer's et al. (1990) conclusion [3] and current study's results has been made. The critical strain increases as the ratio between axial thrust and pipeline bending stiffness decreases.