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Alavi S.M.,Tehran Province Gas Company | Bargi K.,University of Tehran
Electronic Journal of Geotechnical Engineering | Year: 2012

Gas pipelines are important lifelines in a city. Earthquake induced liquefactions and seismic wave propagation are one of the dangers threatening gas pipelines. Intensive damages of pipelines may cause gas leakage and the probable explosion. In this paper, the effects of liquefactions and seismic wave propagation on the buried gas pipelines are analyzed by finite element simulation. Source

Rofooei F.R.,Sharif University of Technology | Jalali H.H.,Sharif University of Technology | Attari N.K.A.,Building Research Institute, Egypt | Kenarangi H.,Sharif University of Technology | Samadian M.,Tehran Province Gas Company
Canadian Journal of Civil Engineering | Year: 2015

A numerical study is carried out on buried steel and high density polyethylene (HDPE) pipelines subjected to oblique-reverse faulting. The components of the oblique-reverse offset along the horizontal and normal directions in the fault plane are determined using well-known empirical equations. The numerical model is validated using the experimental results and detailed finite element model of a 114.3 mm (4==) steel gas pipe subjected to a reverse fault offset up to 0.6 m along the faulting direction. Different parameters such as the pipe material, the burial depth to the pipe diameter ratio (H/D), the pipe diameter to wall thickness ratio (D/t), and the fault–pipe crossing angle are considered and their effects on the response parameters are discussed. The maximum and minimum compressive strains are observed at crossing angles of 30° and 90°, respectively. It is found that the dimensionless parameters alone are not sufficient for comparison purposes. Comparing steel and HDPE pipes, it is observed that HDPE pipes show larger compressive strains due to their lower strength and stiffness. For both steel and HDPE pipes, peak strains increase with increasing D/t and H/D ratio for a constant pipe diameter and fault offset. For a given H/D ratio, compressive strains increase with increasing D/t ratio in HDPE pipes, while in steel pipes considered in this study, this effect is negligible. Finally, the peak strains of the pipes are compared to those suggested by Canadian Standard Association for Oil and Gas Pipeline System, CSA Z662. © 2015(Publisher Name). All Rights Reserved. Source

Jalali H.H.,Sharif University of Technology | Rofooei F.R.,Sharif University of Technology | Attari N.K.A.,Building Research Institute, Egypt | Samadian M.,Tehran Province Gas Company
Soil Dynamics and Earthquake Engineering | Year: 2016

Permanent ground displacement (PGD) caused by surface faulting is considered as one of the most significant hazards affecting buried pipelines. Pipelines crossing reverse-slip faults are subjected to compressive actions (stresses and strains) which can result in buckling of the pipe. In current work, the results obtained from the full-scale laboratory testing and finite element analyses of 4″ (114.3 mm) and 6″ (168.3 mm) steel gas pipes (without internal pressure) buried inside a split box and subjected to a reverse faulting of 0.6 m (pure dip-slip) are presented. These pipes are commonly used in gas distribution lines and networks. The experimental setup, procedure and instrumentation as well as the finite element (FE) modeling of the problem are described in detail. It is observed that the soil failure in the moving part of the split-box occurs along vertical surfaces extending from the sides of the pipe to the ground surface. The experimental results indicate that both pipes exhibit an S-shape deformation with two local buckling sections where the excessive yielding and plastic deformations of the pipes could lead to rupture failure. Both pipes exhibited "diamond-shape" buckled sections. The buckled sections of the pipes in the fixed and moving parts of the split box were unsymmetrical with respect to the fault plane. Using the factor of ovality to measure the pipe cross-section distortion, it is found that the cross-section distortion is more severe for the buckled section of the pipe in the moving part of the split box in comparison to its fixed part. Also, the distance between the buckled sections increases by increasing the pipe diameter, while the distortion of the pipe cross-section increases by increasing the pipe diameter over thickness ratio. Using the FE models that were validated utilizing the experimental results, the maximum equivalent soil-pipe interaction forces and their distribution along the pipes were determined and the results were compared with that of American Lifeline Alliance Guidelines for the Design of Buried Steel Pipe (ALA, 2005) [33]. The obtained maximum bearing force is less than the suggested values by ALA, while the maximum uplift force slightly exceeds those of ALA. The results indicate that for the considered cases, the uplift force is sensitive to the pipe diameter and its relative stiffness, while the ALA (2005, [33]) suggests a constant force for the burial depths considered in this study. © 2016 Elsevier Ltd. Source

Allahkaram S.R.,University of Tehran | Isakhani-Zakaria M.,University of Tehran | Derakhshani M.,University of Tehran | Samadian M.,Tehran Province Gas Company | And 2 more authors.
Journal of Natural Gas Science and Engineering | Year: 2015

Influence zone of the dynamic stray current from subway was determined on parallel and crossed gas pipelines via synchronized potential measurements at different transverse distances from railway right of way. Results showed that the interference magnitudes decrease substantially with increasing the distance. Twenty-four hour monitoring of pipe to soil potential, lead to a new corrosion criterion for the affected pipelines depending on the type of coating used. A procedure based upon potential measurements has been developed for field investigations. Calculations of corrosion rate via Faraday law and weight loss measurements using corrosion coupons were also carried out. © 2015 Elsevier B.V. Source

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