Influence of Boundary Conditions on Response of Pipelines Crossing Reverse Fault Zone

Pipelines are the most common way to transport essential fluids, such as water, oil, and natural gas. A pipeline usually traverses a large geographical area, and it is likely to be exposed to geohazards, which might result in permanent ground deformations. These large deformations can occur due to landslide, lateral spreading, or fault movement. This experimental research focuses on the influence of boundary conditions on the performance of a pipeline in a reverse fault-crossing zone. Pipeline length in a fault area is generally far longer than the length of experimental models; therefore, it is challenging to properly simulate the far-field effect in laboratory studies. Because interactions between the pipe and surrounding soil in the hogging zone (bearing resistance) and sagging zone (uplift resistance) are not similar, a reverse fault-crossing area results in an asymmetric movement. This study presents the results of a series of a laboratory-scaled pipeline buried in a sandy layer with four different end conditions subjected to reverse fault offset: free (moving freely in three directions), axial-free (axially free but laterally fixed), springs (lateral and axial springs), and axial-fixed (axially fixed and laterally constrained by springs). The tests were carried out in a split-box apparatus modeling the reverse faulting under 1g conditions. The results show that the end-joint conditions of the pipe have a significant effect on failure mode of the pipeline. For the spring end joint simulating the bearing, uplift, and axial resistances of surrounding soil, local buckling occurred near the fault plane. Euler’s beam buckling was observed for the pipe with the axial-fixed end joint, and no significant deformation for the pipes with free and axial-free end joints was recorded. Finally, practical implications of the study are discussed, and recommendations are made for applying the results in experimental modeling of buried pipelines in reverse fault area are made.