Innovative analysis of a buried operating pipeline subjected to strike-slip fault movement

Earthquake induced Permanent Ground Deformation (PGD), such as landslides, lateral spreading due to liquefaction and faulting, seriously threaten the safety of buried pipelines, highlighting the need to accurately evaluate their seismic performance within the engineering design practice. Over the last decades, this problem has been addressed numerically using the simplistic beam on Winkler foundation and the more complex continuum model. While the former is unable to model the realistic soil-pipeline interaction for large scale deformations and to capture the pipeline local instabilities, the latter presents significant disadvantages in terms of elevated computational demands and required engineering expertise. This paper presents a parametric analysis of a buried pipeline crossing a strike-slip fault, using the continuum modelling approach, where both soil and pipe contact surfaces are meshed with a similar mesh size guaranteeing solution convergence. Moreover, the introduced submodeling technique allows to focus with a finer mesh on the limited part of the model susceptible to local buckling, permitting to accurately evaluate the critical fault displacement corresponding to this performance limit state. To optimize computational costs, each end of a limited pipe segment crossing the fault is suitably connected to an equivalent-boundary spring, representing the interaction with the rest of the soil-pipeline system. The seismic performance of the buried pipeline is evaluated in function of different critical parameters, such as the fault inclination angle and the pipe internal pressure. The obtained numerical results are accurately compared with data reported in recent research publications and analytical solutions, giving a better insight into the mechanical behaviour of soil-pipeline system under strike-slip faulting. In conclusion, the proposed modelling procedure, including the submodeling technique, can be suitably used to accurately and efficiently analyse the seismic performance of buried pipelines subjected to similar PGD.