Behaviour of pipes subjected to fault movements in unsaturated soils using spring analysis

The damage to pipelines caused by earthquake induced fault movement can be disastrous. Due to the fact that pipelines are generally spread over large geographical areas and exist in the form of a network, it is almost impossible to avoid active faults ruptures across which a huge body of soil can move relative to the pipe displacements during earthquakes. Recent large scale testing performed at Cornell University showed that significant amow1t of strains can be accumulated to fail the pipe at the intersection between the pipe and fault plane in the events of earthquake induced soil displacements. Pipes buried in unsaturated soils can enhance such risk of failure as the effect of suction could be detrimental in some sands as shown by Robert et al, 20 I 0. In the current study, spring analyses were performed to investigate the behaviour of buried pipelines subjecting to strike-slip fault movements in dry as well as partially saturated soils. The spring model was first validated by comparing the computed results to the 3-D finite clement analysis results as well as to the data produced from large scale experiments carried out at Cornell University, US. Analyses are further extended to investigate the effects of fau lt movements on pipes buried in partially saturated soils at different embedded depths in various soil types. The results revealed that spring analysis can predict realistic pipe deformation in dry and partially saturated soils when pipe does not possess excessive ovating or buckling at die fault rupture.