Simulation of Buried Natural Gas Pipelines and Determination of Optimum Safe Depth
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TECHNICAL ARTICLE—PEER-REVIEWED
Simulation of Buried Natural Gas Pipelines and Determination of Optimum Safe Depth Zahra Joneidi . Seyed Alireza Mostafavi . Mohammadreza Motahari
Submitted: 4 February 2020 Ó ASM International 2020
Abstract Buried gas pipelines are vital assets of natural gas transportation system for every country. Therefore, investigation of their potential failure’s roots is prominent. There are different causes for their failure among which imposed loads are the majority. In this study, considering soil as an elastoplastic material and deriving its constitution equation, a steel gas pipeline was modeled in its critical cross section where it passes under a road. Studying the behavior of the axial stress as maximum stress component and pipeline displacement under live and dead loads, a safe depth of 2 m was found so as to decrease and increase failure probability and safety factors, respectively. This height not only negates live loads, it alleviates the effect of dead loads. Keywords Buried pipeline Dead load Live load Road Axial stress Safe buried depth
Introduction Pipelines are vital energy veins of each country, and they are considered as highly sensitive national assets. Huge amount of dangerous fluids is transformed using pipelines with high safety and speed [1–3]. For instance, 97% of produced oil and gas is transformed by pipelines in Canada. However, pipeline failure-related accidents can cause Z. Joneidi S. A. Mostafavi (&) Department of Mechanical Engineering, Faculty of Engineering, Arak University, Ara¯k, Iran e-mail: [email protected] M. Motahari Department of Civil Engineering, Faculty of Engineering, Arak University, Ara¯k, Iran
detrimental financial and mortal tolls. Only in the USA within 1995 to 2014, pipeline failure phenomenon caused 360 tolls, injury of 1365 and in total 7-billion-dollar financial damage [4]. There are different reasons for pipeline failure among which external loads are very critical. With extension of the cities and transportation roads, pipelines have to pass beneath the critical area of the roads where they undergo external loads imposed by vehicle traffic. This seems to emphasize the need for analyzing the safety and for studying failure probability of pipelines [5–7]. There are many efforts from the beginning of the century on analysis of the pipelines. Spangler [8], vastly studying rigid pipelines, found formulations to compute stress and deformation in the pipelines. Noor et al. [9], modeling pipeline under live loads of traffic using an FEM approach and considering both soil and pipeline as elastic materials, found that the force imposed from each tire of the truck is readily independent from other tires. They also found that considering soil–pipe interaction is crucial in computations. Corona and Kyriakides [5] suggested that since pipes bend under the effect of their weight, neglecting their weight can introduce remarkable errors in computations and, therefore, they should not be ignored. Kong and Shuai [10], investigating
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