عنوان مقاله [English]
Buried pipeline networks are designed to transfer water, gas and oil, and collect wastewater in large industrial cities. The significance of these pipelines as lifeline facilities is more obvious in regions with high risk of earthquake damage. Failure of oil and gas pipelines can cause severe economical and environmental problems. Investigations show that damage to buried pipelines is not attributed to load levels of seismological vibrations. Despite damage to surface structures, large fault movements are the main causes of pipeline damage. Many researchers have studied pipeline behavior against those phenomena with simplified assumptions, in which effects of interactions between soil and pipe are ignored. In this research, the behavior of a pipe under normal and strike-slip fault movements, and contact between them, is simulated using FEM modeling to investigate fault movement effects on pipeline failure and to design an appropriate pipeline. Also, to reach an optimized performance, to design pipelines against seismic load and to offer the relevant equations, several parameters, such as pipe diameter, pipe wall thickness, pipe burial depth, crossing angle between pipe axes and fault, unanchored length of pipe and pipe strength, are considered. These models are made up of three different parts. Two of them are soil blocks, which are divided into similar parts by a fault plane. In order to clarify fault movements during earthquake and their effects on pipes, contact and interaction between the two similar soil parts and a slide based on the maximum shear strength between them are applied. The third part is a steel pipe, which passes through the fault plane inside the soil layers. Soil and pipe are connected to each other by appropriate contact elements, so that the outside surface of the pipe interacts with the inside surface of the soil where the pipe is buried. In each part of the models, elasto-plastic materials are used. Therefore, it is possible to evaluate the roles of mentioned parameters by several analyses. The results from parametric analysis on the effects of those faults on buried steel pipelines show that increasing the angle of the pipe axis and fault line, as well as pipe thickness, and decreasing burial depth diminishes the probability of pipe failure crossing active faults. Changes in pipe diameter also affect the pipe strength slightly. Comparison between results of earlier and current research indicates that they are more conservative.