Buried Pipelines

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Vulnerability Assessment of Buried Pipelines

by

Pradeep Kumar Ramancharla, Terala Srikanth, Vasudeo Chaudhary, Chenna Rajaram, Bal Krishna Rastogi,

Santhosh Kumar Sundriyal, Ajay Pratap Singh, Kapil Mohan

Report No: IIIT/TR/2014/-1

Centre for Earthquake Engineering

International Institute of Information TechnologyHyderabad - 500 032, INDIA

March 2014


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VACI/IIIT-H/Report: 04

Assessment of Vulnerability of Installation near GujaratCoast Vis-à-vis Seismic Disturbances

Title: Draft Report on Vulnerability Assessment of Buried Pipelines

International Institute of Information Technology

Hyderabad

Institute of Seismological ResearchGovernment of Gujarat, India

Ministry of Earth SciencesGovernment of India

August 2013

Earthquake Engineering Research CentreInternational Institute of Information TechnologyGachibowli, Hyderabad – 500 032, India


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Participants

From

International Institute of Information Technology, Hyderabad

Ramancharla Pradeep Kumar

Terala Srikanth

Vasudeo Chaudhary

Chenna Rajaram

From

Institute of Seismological Research, Govt. of Gujarat

Bal Rastogi

Santosh Kumar Sandriyal

Ajay Pratap Singh

Kapil Mohan


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Vulnerability Assessment of

Buried Pipelines


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Abstract

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Table of Contents

1.

Introduction………………………………………...……………………………….….……12. Pipeline Scenario in India……………………………………………………….…….……3

2.1 Petroleum pipeline………………………………………………………….…...3

2.2 Gas pipeline……………………………………………………………………...3

2.3 Crude oil pipeline……………………………………………………………….4

3. Pipeline policies and guidelines…………………………………………………….…..…7

3.1 Policy……………………………………………………………………………...7

3.2 Transnational pipelines…………………….……..………………………….…8

3.3 Indian Standards…..……………………………….……………………………8

4. Past pipeline performances…………………………………………………………..…...13

4.1 Seismic Hazard……….……………………………………….……..…………13

4.2 Indian context………………………………………………….……………….13

5. Effects of earthquake on pipelines …….…………………………………………………14

5.1 Continuous pipeline……………………………………………………….......16

5.1.1 Tensile failure………………………………………………………..…16

5.1.2 Local buckling………………………………………………………….16

5.1.3 Beam buckling………………………………………………………….17

5.2 Segmented pipeline…...………………………………………….……………17

5.2.1 Axial Pullout ….……………………………………………………..…17

5.2.2 Crushing of bell and spigot joints…………………………………….19

5.2.3 Flanged joint failure…...……………………………………………….19

5.2.4 Circumferential flexural failure and joint rotation………………….20

6.

Vulnerability Assessment of buried pipelines…….....………………………………….216.1 Location 1-5………………..……………………………………...…….………21

6.2 Parametric study………………..………………………...……...…….………70

7. Conclusions…...…………………………………………………………………………….81

8. References…………………………………………………………………...……………...83


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List of figures

1. A map of India’s Oil product pipelines of Gujarat state ...………………………….22. India’s product pipelines (Source: Petronet India Ltd)………………...……………5

3. Crude oil and gas pipelines in India ………………………………………………….6

4. Effect of landslide on pipeline resting tensile strain (ASCE, 1984) ……………….16

5. Locally buckling steel gas pipeline in the compression zone at North slope ofTerminal Hill in 1994 Northridge earthquake. (EERI, 1995)….....…………………17

6. Beam buckling of a water pipeline made of iron. (USGS Photo Library) ……..…18

7. Axial pull-out at the joint of a water supply pipeline at Tangshan East Water

Works in Tangshan Earthquake 1976 (EERL, 2004) ……………………….…….…18

8. Failed cast iron pipe due to failure of bell and spigot joint at Navlakhi port due tolateral spread in 2001 Bhuj earthquake (ASCE,2001)………………………………………………..……………………………………19

9. Flanged joint pipe failure. (ASCE, 1997) ……………………………………..…..…20

10. Leaking at bell and spigot joint of water supply pipeline due to bending atShippy Ghat, Port Blair in M9.0 Sumatra earthquake of 2004 (Photo: Suresh RDash) ………..…………………………………………………………………………..20

11. a) Pipeline crossing parallel to the ground movement. b) Pipeline crossingtransverse to the ground movement…………………………………………………24




15. a) Pipeline crossing parallel to the ground movement. b) Pipeline crossing

transverse to the ground movement…………………………………………………6216. Total strain vs pipe thickness for pipe diameter is 12 “……………………………71

17. Total strain vs pipe thickness for pipe diameter is 18 “……………………………72




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List of Tables

1.

Summary of IOC pipelines in the last year ………...………………………..……….5 2. Details of six pipelines by Reliance Industries Ltd ………….………………………6

3. Earthquake impact on Gujarat state during 1901-2002……….……………………11

4. Maximum strains in the pipe in compression and tension in four cases ………...32

5. Maximum strains in the pipe in compression and tension in four cases …...……41

6. Maximum strains in the pipe in compression and tension in four cases.………...50

7. Maximum strains in the pipe in compression and tension in four cases ...………60

8. Maximum strains in the pipe in compression and tension in four cases...………69

9. Strains due to internal pressure and temperature change with pipe wall thicknessfor pipe diameter is 12” ………...……………………….……………………..…...…70




13. Longitudinal strains in the pipe due to tension and compression for pipediameter is 12” ………...……………………...………….……………………..…...…74




17. Total strains in the pipe due to tension Pipe diameter is 12” and faultdisplacement 1.5m………...……………………………..……………………..…...…76




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25. Total strains in the pipe due to tension Pipe diameter is 12” and PGA =0.45g …79

26. Total strains in the pipe due to tension Pipe diameter is 18” and PGA =0.45g …79

27.

Total strains in the pipe due to tension Pipe diameter is 24” and PGA =0.45g …80 28. Total strains in the pipe due to tension Pipe diameter is 30” and PGA =0.45g …80


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1. Introduction

Pipelines have been acknowledged as the most reliable, economic and efficientmeans for the transportation of water and other commercial fluids such as oil and gas.These pipeline systems are commonly used to transport water, sewage, oil, natural gasand other materials. They are often referred to as “lifelines” since they carry materialsessential to the support of life and maintenance of property. The earthquake safety ofburied pipelines has attracted a great deal of attention in recent years. Pipelines areimportant lifeline facilities spread over large area and encounter a range of seismichazards and soil conditions. Many buried pipelines in India run through high seismicareas and therefore are exposed to considerable seismic risk. Pipelines running throughhigh seismic zones should be designed in such a way that they remain functional even

after subjected to high intensity earthquake shaking. Pipeline systems are commonlyused to transport water, sewage, oil, natural gas, etc over a large area and encounter avariety of seismic hazards and soil conditions. Pipelines are generally buried belowground primarily for aesthetic, safety, economic and environmental reasons. The gasand liquid fuel pipelines are generally welded at the joints to act as a continuouspipeline. Pipelines having rigid joints (i.e., strength and stiffness of joints are more thanthat of pipe barrel) are generally referred to as continuous pipelines (e.g., steel pipewith welded connection). On the other hand, the water supply pipelines withmechanical joints are generally treated as segmented pipelines. These segmentedpipelines consist of pipe segments that are connected by relatively flexible connections(e.g., cast iron with bell and spigot joint).

Modern pipelines manufactured with ductile steel with full penetration butt welds at joints possess good ductility. It has been observed that the overall performance recordof oil and gas pipeline systems in past earthquakes was relatively good. Howevercatastrophic failures did occurs in many cases, particularly in areas of unstable soils.Failures have mostly been caused by large permanent soil displacements (FEMA-233).

A pipeline transmission system is a linear system which traverses a large geographicalarea, and soil conditions thus, is susceptible to a wide variety of seismic hazards.Ruptures or severe distortions of the pipeline are most often associated with relative

motion arising from fault movements, landslides, liquefaction, loss of support, ordifferential motion at abrupt interfaces between rock and soil. Notable the mostcatastrophic damages are the once resulting from faulting and liquefaction.

India is currently making huge investments in pipelines. Considering high seismicity ofour country, it is important to ensure seismic safety of buried pipelines. Gujarat is oneof the high earthquake prone states in India. And in last few years many state owned


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and private organizations had build up their pipeline networks across the state. Owingto these facts the performance of buried and above ground pipeline structures subjectedto faulting and soil liquefaction effect and other seismic hazards have become animportant subject of study. Gujarat State Petronet Ltd organization intends to expandsits grid to 2200kms with an outreach to all the 25 districts of Gujarat thereby enabling

industry, households and transportation to drive the benefits of an environmentfriendly fuel.

Figure 1. A map of India’s Oil product pipelines of Gujarat state

This report illustrates the performance of one of the high pressure gas pipeline in thestate of Gujarat, under the fault movement and soil liquefaction. Based on the resultfrom the study some recommendations are made to minimize the effect of earthquake

on the existing pipeline.

Important characteristics of buried pipelines are that they generally cover large areasand are subject to a variety of geotectonic hazards. They can be damaged either bypermanent movements of ground (i.e., PGD) or by transient seismic wave propagation.Permanent ground movements include surface faulting, lateral spreading due toliquefaction, and land sliding. Although PGD hazards are usually limited to small


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regions within the pipeline network, their potential for damage is very high. On theother hand, wave propagation hazards typically affect the whole pipeline network, butthe rate of damage is lower (i.e., lower pipe breaks and leaks per unit length of pipe).

2.

Pipeline Scenario in India2.1

Petroleum and gas pipelines in India

In view of the strategic importance of the oil & gas industry and oil security, andrecognizing the increasing demand for energy, to fuel economic growth, theGovernment of India (GOI) has developed the ‘India Hydrocarbon Vision 2025’for theoil & gas industry. This vision statement creates a road map that guides the Indianpolicy on oil & gas up to the period 2025, forms the backbone and lays the frameworkfor the policy initiated for the hydrocarbon sector; comprising the different segmentsincluding pipelines (both national and transnational) in a structured and organized

manner. Details below present, in brief, the current status of the pipelines systems inIndia - for crude oil, products pipelines and gas.

Pipelines occupy a key position in any petroleum and gas sector’s logistics. Both publicsector units and private sector players tried to ensure control over this safe andeconomical mode of transportation in India. Initially each of these players had plans oflaying their own pipelines, but the GOI wanted to ensure systematic growth, thusleading to the creation of Petronet India Ltd (PIL), a financial holding company, in 1998,with the objective of constructing a refined petroleum product pipeline infrastructure inthe country. PIL is a joint venture organization of India’s state owned refineries,financial institutions and private sector players on a ‘common career’ basis. It is

presently building pipelines that are expected to add 500,000 b/d to India’s current325,000 b/d of pipe-line capacity for the transportation of refined petroleum products.Presently, a total of eight pipeline projects are being handled by PIL some of which arealready in operation while some others are either under execution or in the planningstage. India transports just over 45%of its petroleum products via pipe-lines. A map ofIndia’s Oil product pipelines is shown in Figure 1.

2.2 Gas pipelines

The Gas Authority of India Ltd (GAIL) – now called GAIL India Ltd– a leading public

sector enterprise, is the largest gas transmission and marketing company in India.Today GAIL owns over 4000km of pipeline and has about 95%market share in theNatural Gas business in India. Also, more than half of the total urea production in Indiais gas-based, out of which GAIL contributes more than 90%,thus making a significantcontribution to India’s agricultural sector also. The company also completed the world’slongest (1200 km) and India’s first cross country LPG pipe-line from Jamnagar to Loni,near Delhi. There exists a total of 3331km of LPG pipelines in the country, with a


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throughput capacity of 8304MMtpa, work on some of which is still in progress. GAIL isnow in the process of doubling the throughput capacity of its main Hazira–Bijaipur- Jagdishpur(HBJ) pipeline. Work on the capacity expansion began in 2002 and willeventually raise the capacity of the pipeline from about 1.1 Bcf/d to2.1 Bcf/d. GAIL alsoplans a new distribution network in West Bengal and a pipeline which could connect

Kolkata with Chennai. India is investing heavily in the infrastructure required tosupport in-creased use of Natural Gas. This has become even more so with the majordevelopment in December 2002when Reliance announced its discovery of largevolumes of Natural Gas in the Krishna-Godavari basin, offshore from Andhra Pradesh,around India’s Southeast coast. New reserves from this find are estimated at about 5Tcf. Cairn Energy also reported finds in late 2002 offshore Andhra Pradesh as well asGujarat, which contains reserves estimated at nearly 2 Tcf. State owned ONGC, whichwas originally engaged in the gas production from the Bombay-High offshore fields,has further added to gas discoveries on India’s East coast as well. Shell has signed aMemorandum of Understanding with the State Government of Uttar Pradesh in

Northern India for the development of a Natural Gas distribution infrastructure. Inaddition, there are regional gas grids of varying sizes in Gujarat (CambayBasin),Andhra Pradesh (Krishna-Godavari Basin), Assam(Assam-Arakan Basin),Maharashtra (Ex-Uran Ter-minal), Rajashthan (JaisalmerBasin), Tamilnadu(CauveryBasin), and Tripura (ArakanBasin).

Meanwhile, GSPL(Gujarat State Petronet Ltd)is implementing a 1600 km long gas gridin the state of Gujarat. GSPL was incorporated as a special purpose vehicle by theGujarat State Petroleum Corporation in December 1998, especially to implement the gas

grid for the trans-mission of LNG from import terminals to demand centres across thestate.

2.3 Crude oil & petroleum product pipelines

Indian Oil Corporation Ltd.(IOCL) operates the largest net-work of crude and productpipelines and transports petroleum products to the various major demand centres ofthis geographically vast country and feed four major inland re-fineries. The pipelinedivision of IOCL has in-house capabilities of executing pipeline projects from concept tocommissioning without any external support, whatsoever. Proven project techniques

and tools are used in project management to ensure a high level of quality, productivity,time scheduling and cost control.

A summary of IOC pipelines, as existed at the end of last year is given below:


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Table 1. Summary of IOC pipelines in the last year

Figure 2. India’s product pipelines (Source: Petronet India Ltd)

Oil India Ltd. transports all crude oil produced in North-East India to refineriesvia a 1,157 km pipeline. The Oil& Natural Gas Corporation (ONGC),India’s singlelargest crude producer, has a 7900 km onshore pipeline net-work while its offshoreactivities include a 3500 km pipeline network. Bharat Petroleum Corporation Ltd(BPCL)

and Hindustan Petroleum Corporation Ltd (HPCL) also have product(over 250 km) andcrude and product pipelines (over 750 km) respectively in operation as well, in additionto having partnerships with PIL in this economic mode of transport. The CIPL (CentralIndia Pipeline Project), originally intended to be executed by PIL, has now beenapproved for award by the PIL Board to the joint venture of IOCL and RelianceIndustries Ltd (RIL) – previously called Reliance Petroleum Ltd (RPL) -on a build–own–transfer–operate basis. In their proposal for CIPL, IOC and RPL have estimated a cost of


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about US$0.32 billion by stripping the spur lines, planned for Bhopal, Indore andChittorgarh. Under the policy for the development of petroleum product pipelines‘Common User Principle’, six pipe-lines to be put up by RIL have been approved. Theseinclude:

Table 2. Details of six pipelines by Reliance Industries Ltd

Pipelines between refineries and major urban centres are replacing rail as the mainmode of transportation. Some of the other pipeline projects for crudes and productsunder consideration/ implementation are:

• Vadinar- Bina (crude)• Mundra-Bhatinda (crude)• Bina –Kanpur• Paradip-Rourkela• Bhatinda-Pathankot


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Figure 3. Crude oil and gas pipelines in India

3. Pipeline Policies and Guidelines

3.1 Policy

On September 29, 2003 the GoI announced the draft pipeline gas policy whichenvisaged the laying of 7,000 km of pipeline network for gas transportation at a cost ofaround MMUS$ 3902.86 in the next 5-6 years. As a part of this policy, GOI proposes aNational Gas Grid on the pattern of the National Power Grid to manage the distributioneffectively. While individuals will be permitted to lay pipelines for distributionpurposes, say up to 100 km, but if the length is beyond the prescribed limit theconstruction would be carried out in accordance with the ‘Common Carrier Principle’ toavoid duplication and wasteful expenditure. The main objective of the draft policy,

presently undergoing finalization with the GOI, is to put in place a distribution systemfor carrying gas, the availability of which is likely to improve considerably, it havingbeen struck at several places, as mentioned above, with arrangements for the movementof liquefied Natural Gas (LNG) having been tied up indefinitely. Under the proposedpolicy, all trunk pipelines covering more than one state or operating at a pressure morethan the notified level will be build or managed by a company to be decided by the GOIbut, until it is notified, by GAIL India Ltd. Seizing the opportunity, GAIL has un-veileda MM US$ 4336.51 plan to build a 7,890 km gas grid as shown in Figure 2, along with acompletion schedule. The rationale: gas grids in several countries like Italy, France,Turkey and also in China and Korea have been built by the NOCs, because of issues of

safety and security. The policy envisages appointment of a Regulator under thePetroleum Regulatory Board Bill 2002 for regulating transmission, distribution, supplyand storage systems for Natural Gas/LNG and to promote development of the sector.The Regulator will ensure access to gas pipelines on non-discriminatory commoncarrier principle for all users. And the tariff for the transmission pipelines anddistribution pipelines would be approved by the Regulator. Pipelines in India havetraditionally operated at 100%capacity (since these are captive pipelines of oilcompanies). However, where pipelines are operated under a common carrier principleas mooted in the draft pipe-line policy, they may in reality be faced with uncertainty inutilization, arising from demand supply dynamics. Since these are long life projects,high capacity utilization over long periods becomes a pre-requisite for financial

viability. Probably the key issue that requires resolution is the demand by the financialinstitutions that the proposed pipe-line projects enter into long term ‘Takeor Pay’contracts. According to some, this demand would largely violate the common carrierprinciple, which at-tempts to ensure equitable access to all users. The key concern isprice.


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The principles governing the tariff structure should ensure adequate competitionamong various mode combinations, fair return to investors (i.e., returns commensuratewith the risks assumed), equitable access to all users and equitable costs to consumers.While it is easy to enunciate the broad principles, implementing this could be anextremely complex task, given the peculiarities of the situation and the relative lack of

time available for formulation of policy and implementation.

3.2 Transnational pipeline

In addition to the pipeline projects being developed within the country as mentionedabove, the GOI is trying to strike alliances to import piped gas from gas-rich countriesin the vicinity, such as Iran and Turkmenistan in central Asia, Qatar and Oman in WestAsia and neighbouring Bangladesh. Proposals for gas pipelines from Iran andBangladesh are under active consideration. The first proposition is to connect Iran’sSouth Pars field with the HBJ pipeline. The second preposition is to connectBangladesh’s Bibiyana gas field in North Eastern Bangladesh with India’s Northern Gasmarkets. Unocal Corporation and its subsidiaries in Bangladesh have submitted a gasexport pipeline proposal, known as The Bangladesh Natural Gas Pipeline Project, andthe proposal is pending approval from the Bangladesh Parliament. The recent large gasdiscovery in Myanmar (OVL and GAIL collectively hold a 30% stake) has opened up anew avenue for importing gas into India. The emergence of this option would have asignificant impact on the business dynamics of the proposed transnational pipelinesfrom Iran and Bangladesh. Another crucial factor in this segment should be theprogress made by the GOI in its efforts to improve the Geopolitical scenario in theregion. GOI’s pricing policy (under formulation) would play a crucial role in thedemand supply scenario of gas, as the user industries have alter-native options to gas.

Once GOI clarifies its stand on gas pricing, LNG policy and the common carrierprinciple, significant, positive implications for the commercial aspects of the natural gasindustry in India should be forthcoming.

3.3 Indian Standards

The following codes and reports have been used in the preparation of this report.

1. IS 15663(Part 1):2006 This code covers requirements and recommendations for thedesign, materials, construction and testing of pipelines made of steel and used in thetransportation of natural gas and re-gasified liquid natural gas (RLING).

2. IS 15663(Part 2):2006 The code covers the minimum requirements for design,installation and testing of pipelines of steel, crossing roads, railways, water courses andother buried services.

3. IS 15663(Part 3):2006 This code covers requirements for pre-commissioning andcommissioning of pipelines.


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4. IS 15654:2006 The standard provides guidelines for the definition, specification,performance analysis, and application of systems used for supervisory control and dataacquisition for oil and gas pipe lines.

5. IS 15655:2006 This standard enlists various types of telecommunication facilities

required for smooth and efficient operation and maintenance of oil and gas pipelines.

6. IS 15667:2006 This standard applies to data-acquisition and trend-monitoring systemsfor gas turbine installations and associated systems.

7. IS 15664:2006 This standard specifies procedures and rules for the conduct andreporting of acceptance tests in order to determine and/or verify the power, thermalefficiency and other performance characteristics of gas turbine power plants.

8. IS 15666(Part 1):2006 This standard covers terms and definitions relevant to theprocurement of gas turbine systems.

9. IS 15666(Part 2):2006 This standard specifies the standard reference conditions andstandard ratings for gas turbines.

10. IS 15666(Part 3):2006 This standard covers the design requirements for theprocurement of all applications of gas turbines and gas turbine systems, including gasturbines for combined cycle systems and their auxiliaries, by a purchaser from apackager. It also provides assistance and technical information to be used in theprocurement.

11. IS 15666(Part 4):2006 This standard provides guidelines for procurement of gasturbines with consideration of the fuel quality and of the environmental performance.

Guidance is given to both the packager and purchaser on what information should beprovided with regard to the fuel used by a gas turbine, and with regard to the type ofinformation necessary to quantify the expected environmental impact.

12. IS 15666(Part 5):2006 This standard specifies requirements and givesrecommendations for the design, materials, fabrication, inspection, testing andpreparation for shipment of packaged gas turbines for use in drilling, production,refining and the transport by pipelines of petroleum and natural gas. It is applicable tothe procurement of gas turbines and gas turbine systems, including gas turbines forcombined cycle systems, and their auxiliaries by a purchaser from a packager.

13. IS 15666(Part 7):2006 This standard specifies the information that needs to besubmitted during the proposal and contract stages of a project for the entire scope ofsupply for which the packager will assume technical and contractual responsibility.

14. IS 15666(Part 8):2006 This standard states the principles for systems and proceduresto assure the integrity of a packager’s product and services. It gives guidance on theinspection, testing, installation and commissioning required for the package and


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packaged equipment. It outlines the responsibilities between the purchaser andpackager for inspection, coordination, reporting and recording.

15. IS 15666(Part 9):2006 This standard provides a basis for exchange of informationabout reliability, availability, maintainability and safety between gas turbine

manufacturers, users, consultants, regulatory bodies, insurance companies and others.It also describes component life expectancy, repairs and criteria for determiningoverhaul intervals.

16. IS 15665:2006 This standard gives terms and definitions used in the field of gasturbines and applies to open-cycle gas turbines, closed-cycle, semiclosed-cycle andcombined-cycle gas turbines.

17. IS 15657:2006 This standard specifies requirements for centrifugal pumps, includingpumps running in reverse as hydraulic power recovery turbines, for use in petroleum,petrochemical and gas industry process services.

18. IS 15661:2006 This standard specifies requirements and gives recommendations forthe design, materials, fabrication, inspection, testing and preparation for shipment ofcentrifugal compressors for use in the petroleum, chemical and gas service industries.

19. IS 15659(Part 1):2006 This standard specifies requirements of plant applied externalthree layer extruded polyethylene and polypropylene based coatings for corrosionprotection of welded and seamless steel pipes for pipeline transportation of gas andliquid hydrocarbons in the petroleum and natural gas industries.

20. IS 15659(Part 2):2006 This standard specifies the requirements for qualification,

application, testing and handing of materials for plant application of single layer FusionBonded Epoxy (FBE) coatings applied externally for the corrosion protection of baresteel for use in pipeline transportation systems for the petroleum and natural gasindustries.

21. IS 8062:2006 This code deals with general principles and requirements for cathodicprotection system for prevention against corrosion of external underground buriedsurface of metallic high pressure hydrocarbon product pipeline/structure. Thisstandard is intended to serve as a guide for establishing minimum requirements forcontrol of external corrosion on pipeline/structure system.

22. IS 15678:2006 This code provides a uniform authentic reference to the pipelineoperators which shall help them in taking decisions about selection of appropriateMagnetic Flex Leakage (MFL) tool for inline inspection to assess the health of thepipeline segment in quantifiable terms besides keeping them fully aware as to what bestcan be expected out of intelligent pigging inspection.

23. IS 15679:2006 This code covers the minimum requirements of materials, equipmentsand accessories for hot tapping and stopple plugging/line plugging operations of


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onshore natural gas pipelines. It covers the minimum safety requirements to bemaintained during welding, cutting and plug setting, etc, while carrying out the hottapping and stopple plugging/line plugging operations on pipelines.

24. IS 15672:2006 This standard provides guidance on selection, installation, calibration,

performance and operation of Corioils meters for the determination of mass flow,density, volume flow and other related parameters of fluids, synonymous for liquidsand gases.

25. IS 15673:2006 This standard specifies the requirements for the construction, methodsof pressure tapping, working ranges with normal values of minimum/maximum flowrates and permissible errors for rotary piston meters.

26. IS 15674:2006 This standard covers multipath ultrasonic transit-time flow-meters,used for custody transfer measurement of natural gas for gas temperature between -10˚to 55˚C.

27. IS 15675:2006 This standard specifies the geometry and method of use (installationand operating conditions) of orifice plates when they are inserted in a conduit runningfull to determine the flow rate of the fluid flowing in the conduit.

28. IS 15676:2006 This standard specifies the requirements of dimensions, ranges,construction, performance, calibration and output characteristics of turbine meters forgas flow measurement for custody transfer. It also specifies installation conditions,leakage testing and pressure testing and provides recommendations for use, fieldchecks & perturbations of the fluid flowing.

29. IS 15677:2006 This code gives guidance on the specification, design, installation,operation and maintenance of metering systems for high accuracy flow measurement,estimation of uncertainty, secondary instrumentation, gas properties related to meteringof natural gas and related safety aspects. These guidelines cover five types of metersnamely orifice, turbine, ultrasonic, rotary and coriolis.

30. IS 15729:2007 This code covers the commissioning, operation and maintenance andsafety aspects of natural gas pressure regulating and metering terminal.

The table below shows the locations of the different earthquakes that have occurred inthe past.

Table 3. Earthquake impact on Gujarat state during 1901-2002

DateMagnitude

(Richter)

Intensity(MSK) &Location

Impact Source

16 June Mw 7.5 X 23.60N, About 3,200 people were killed and Bilham, ‘99


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1819 69.60E dozens of towns and villages weredestroyed in kutchh and adjoiningparts of southern Pakistan. Theearthquake resulted in great surfacedeformation including a 90-kilometer

stretch that was uplifted about 4m,called the Allah Bund. The shock wasfelt throughout South Asia as far asKolkata.

13 August1821

5V 22.70N,

72.70EKaira-Daman-Ahmedabad areaaffected.

USGS&

NEIC

19 August1845

6VII 23.80N,

68.90ESouth-east of lakhpat kutchh Districtaffected.

USGS&

ASC26 April

18486

VII 24.40N,72.70E

Damage in the Mount Abu area.USGS

&ASC

29 April1864

5VII 22.30N,

72.80ESurat-Ahmedabad area affected.

USGS&

ASC

14 January1903

624.00N,70.00E

North-east of kachchh Districtaffected.

USGS&

ASC

21 April1919

5.5VIII

22.00N,72.00E

Bhavnagar District affected. USGS&ASC

14 July1938

5VI 22.40N,

71.80EPaliyad region in Bhavnagar Districtaffected.

USGS&

ASC

23 July1938

5.5VII 22.40N,

71.80EFelt at Rajkot, Morbid andVikramgad.

USGS&

ASC31

October1940

Ms 5.8 23.70N,69.10E Kutchh District affected. ASC

21 July1956

6.1

115 people killed and hundredsinjured. 1,350 buildings destroyed atAnjar alone. Felt over an area with aradius of 330 Km and as far as

GSI


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Mumbai and Hyderabad (Pakistan).

23 March1970

Ms 5.4

26 people killed and 200 peopleinjured in Bharuch and theneighbouring villages. Heavy

damage in Bharuch city. Groundfissures reported over a distance of20Km and large amounts of waterand sand emitted from them. Thequake was also felt in Ankleshwar,Bhavnagar, Surat and Vadodaracities.

ANSS&

ASC

4. Past Pipeline Performances4.1 Seismic Hazard

A pipeline transmission system being a linear system which traverses a largegeographical area, and soil conditions thus, is susceptible to a wide variety of seismichazards. The major seismic hazards which significantly affect a pipeline system are: i)ground failure, ii) ground motion and iii) others miscellaneous effects. While groundfailure includes faulting, liquefaction and earthquake induced landslides, tsunamis, andother affect of supporting and surrounding structures are usually placed undermiscellaneous hazards. Ruptures or severe distortions of the pipeline are most often

associated with relative motion arising from fault movements, landslides, liquefaction,loss of support, or differential motion at abrupt interfaces between rock and soil.Notably the most catastrophic damages are the ones resulting from faulting or groundrupture. Owing to these facts the performance of buried and aboveground pipelinestructures subjected to faulting and other seismic hazards have become importantsubject of study.

4.2 Indian Context

Currently, India has 7,000 km of pipelines. The oil and gas pipeline infrastructure is

being accorded top priority by the nation's planners and a network of these pipelinescriss-crossing the nation has been planned. The pipeline market itself is estimated to bearound US$ 9 Billion over a period of five-six years. The National Gas Grid beingimplemented by GAIL (India) Ltd, which is expected to take three-four years to reachcompletion, will lay a 17,000 km pipeline network. The proposed oil pipeline network,on the other hand, is expected to build a pipeline network spanning over more then


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5,000 km. These projects will give an enormous boost to the pipeline demand in thecountry.

Notably, India has had more than five moderate earthquakes (Richter Magnitudes ~6.0-7.5) since 1988. As noted in IS 1893 Himalayan-Nagalushai region, Indo-Gangetic Plain,

Western India, Kutch and Kathiawar regions are geologically unstable parts of thecountry, and some devastating earthquakes of the world have occurred there. A majorpart of the peninsular India has also been visited by strong earthquakes.

From the past seismic performance of pipelines in various other countries it can benoted that the consequences of pipeline failure due to earthquakes could be anexaggerated one, particularly so for India, both in terms of economic and social aspects.Thus implementing the seismic design considerations at the current phase of Indianpipeline scenario is absolutely essential.

5. Effects of earthquake on pipelines

The failure of pipelines during past earthquakes is described below.

a) 1971 San Fernando Earthquake: It resulted in direct losses to the pipeline systems bydamaging a 1.24 m diameter water pipeline at nine bend and welded joints. Ductilesteel pipelines were able to withstand ground shaking but could not withstand grounddeformation associated with faulting and lateral spread. Eleven transmission pipelineswere damaged by liquefaction induced lateral spread and landslides. Eighty breaksoccurred to the underground welded steel transmission pipeline located in the upper

San Fernando Valley, the most serious in an old oxyacetylene-welded pipeline.Although located in an uplift zone the failure was caused by compressive forceswrinkling the pipes.

b) 1983 Coalinga Earthquake: It caused numerous breaks in the natural gas line butfires did not occur since the main valve was closed manually shortly after theearthquake. Several pipeline failures occurred in oil drilling and processing facilities. Ingeneral it was noted that most pipe breaks occurred at pipe connections.

c) 1987 Whittier Narrows Earthquake: Damages during this earthquake were usuallylimited to sections that were corroded or anchored at two locations which experienced

large lateral relative displacement. Southern California Gas reported 1411 gas leakswere directly caused by the earthquake. Portions of the California State University, LosAngeles were without gas for 12 weeks. Five fires were reported; three of these wereattributed to gas leaks.

d) 1989 Loma Prieta Earthquake: This Magnitude 7.1 earthquake caused failure ofmany pipelines. Damage consisted primarily of broken water lines. Broken waterlines


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occurred at the Ford plant from liquefaction and excessive soil pressures. At the Port ofOakland located on the east side of the San Francisco Bay on fill all water lines brokeand fire lines ruptured eliminating fire fighting protection.

e) 1992 Big Bear Earthquakes: Two earthquakes occurred in San Bernadino County,

California, a magnitude 7.5 another of magnitude 6.6. These two events were followedby numerous aftershocks. Horizontal fault rupture displacement associated with thisevent was from 5 to 9.5 feet. Most pipeline damage was associated with the rupturezone.

f) 1994 Northridge Earthquake: This event caused about 1,400 pipeline breaks in theSan Fernando Valley area. Outside the zone of high liquefaction potential, the dispersedpattern of breaks is attributed to old brittle pipes damaged by ground movement. In theOn Balboa Boulevard a 0.5588m pipe suffered two breaks, one in tensile failure and theother in compressive failure. These pipe failures were located in a ground rupture zoneperpendicular to the pipeline. Leaking gas ignited at several locations. Some brokenwater and gas lines were found to have experienced 0.1524 to 0.3048 m of separation inextension. The area experienced widespread ground cracking and differentialsettlements. A 2.159 m sewage pipe ruptured in the Jensen Filtration.

g) 1995 Hyogoken-Nanbu Earthquake: Takarazuka City was also heavily damaged.The damage on the water supply pipelines was serious and 203 pipeline damages werereported. Although Sakasedai district has the area of almost 1km square, 30 pipelinedamages (pipe material was DCIP) occurred in the 1995 Hyogoken-nanbu earthquake.Almost 50% of damages were occurred in unliquefied ground.

h) 1999 (Mw 7.4) Kocaeli, Turkey Earthquake: Substantial water supply damageoccurred in many cities. For example, the entire water distribution system in Adapazariwas damaged. One of them, a water pipe made of steel with a diameter of 2.4 m,damaged at Kullar due to right-lateral strike-slip. A butt-welded Thames raw watersteel pipeline 2.2 m in diameter crosses the Sapanca Segment of the North Anatolianfault and was damaged at the fault crossing. Damage was observed at three locationswhere a small surface leak was observed in the pipe at point near the fault crossing; asignificant leak occurred at yet another point and a minor leak happened at the bend ofpipe.

i) 1999, the Chichi Earthquake: In Taiwan many buried water and gas pipelines weredamaged at many sites. It was reported that buried gas pipelines underwent bendingdeformation due to ground displacement at a reverse fault near the Wushi Bridge about10 km south of Taichung. The bending deformation in a 100A-size pipeline was V -shaped, with the pipeline being bent at three points. The deformation of a 200A-sizepipeline was Z-shaped, with the pipeline being bent at two points. There have beenvirtually no cases of substantial deformation comparable to this case in gas pipelinescomprised of welded steel pipes.


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The main seismic hazards that are responsible for pipeline failure can be described as:

i) Seismic wave propagation

ii) Abrupt permanent ground displacement (faulting)

iii) Permanent ground deformation (PGD) related to soil failures

a) Longitudinal PGD

b) Transverse PGD

c) Landslide

iv) Buoyancy due to liquefaction

The main failure modes of both continuous and segmented pipelines are summarized inthe following.

5.1 Continuous pipeline

5.1.1 Tensile failure

Tensile strain in the pipeline can arise due to any of the seismic hazards (e.g., faulting,landslide, liquefaction, and relative ground motion) at pipe supports. Figure belowillustrates the effect of landslide on the pipeline resting high tensile strain.

Figure 4. Effect of landslide on pipeline resting tensile strain (ASCE, 1984).

5.1.2 Local buckling

Local buckling or wrinkling in pipeline occurs due to local instability of the pipe wall.Once the initiation of local shell wrinkling occurs, all subsequent wave propagation and


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geometric distortion caused by ground deformation tend to concentrate at thesewrinkles. Thus, the local curvature in pipe wall becomes large and leads tocircumferential cracking of the pipe wall and leakage. This is a common failure modefor steel pipes. Figure below illustrates local buckling of a 77 inch welded steel pipeduring the 1994 Northridge earthquake.

Figure 5. Locally buckling steel gas pipeline in the compression zone at North slope ofTerminal Hill in 1994 Northridge earthquake. (EERI, 1995)

5.1.3 Beam buckling

Beam buckling of a pipeline is similar to Euler buckling of a slender column; the pipeundergoes an upward displacement. The relative movement is distributed over a largedistance and hence the compressive strains in the pipeline are not too large and thepotential for tearing of the pipe wall is less. For this reason, beam buckling of a pipelinefor a ground compression zone is considered more desirable than local buckling. Beambuckling generally occurs in pipelines buried at shallow depths of about 3 feet or less.This can also happen during post-earthquake excavations, which are carried out

deliberately to relieve compressive strain in the pipes. Figure-4 shows beam buckling ofa water pipeline made of iron during the M7.8 San Francisco earthquake in 1906.

5.2 Segmented pipeline

5.2.1 Axial pull-out


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In the areas of tensile ground strain the common failure mechanism of a segmentedpipeline is axial pull-out at joints, since the shear strength of joint caulking material ismuch less than that of the pipe. Figure shows a 30cm diameter cast iron pipeline pulledapart 25cm during 1976 Tangshan earthquake.

Figure 6. Beam buckling of a water pipeline made of iron. (USGS Photo Library)

Figure 7. Axial pull-out at the joint of a water supply pipeline at Tangshan East WaterWorks in Tangshan Earthquake 1976 (EERL, 2004)


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5.2.2 Crushing of bell-and-spigot joints

In areas of compressive strain, crushing of bell-and-spigot joints is a very commonfailure mechanism. Figure shows the failure of a cast iron pipe due to failure of bell andspigot joint at Navlakhi port area during Bhuj earthquake of January-26, 2001.

Figure 8. Failed cast iron pipe due to failure of bell and spigot joint at Navlakhi port dueto lateral spread in 2001 Bhuj earthquake (ASCE, 2001)

5.2.3 Flanged joint failure

In the areas of tensile ground strain, flanged joint pipeline may fail at joint due to

breaking of the flange connection. Figure shows a flanged joint pipe failure due tohigher tensile strain.


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Figure 9. Flanged joint pipe failure. (ASCE, 1997)

5.2.4 Circumferential flexural failure and joint rotation

When a segmented pipeline is subjected to bending induced by lateral permanentground movement or seismic shaking, the ground curvature is accommodated by somecombination of rotation of joints and flexure in the pipe segments. The relativecontribution of these two mechanisms depends on the joint rotation and pipe segmentflexural stiffness. Figure shows the pipeline leaking at its joint due to excessive bendingin 2004 Sumatra earthquake.

Figure 10. Leaking at bell and spigot joint of water supply pipeline due to bending atShippy Ghat, Port Blair in M9.0 Sumatra earthquake of 2004 (Photo: Suresh R Dash)


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6. Vulnerability assessment of buried pipelines

6.1 Location 1-5

Today, underground conduits serve in diverse applications such as sewer lines, drain

lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, coalslurry lines, subway tunnels, and heat distribution lines. Among these seismic design ofburied pipeline has great importance in the field of lifeline engineering. The pipelinesare usually buried below ground for economic, aesthetic, safety and environmentalreasons. In certain circumstances it may be required to take those pipes above groundbut this case is relatively uncommon. Generally the oil and gas pipelines are designedand constructed as continuous pipelines, while water supply pipelines are constructedas segmented pipelines.

Failures have mostly been caused by large permanent soil displacements.

This section discusses seismic analysis method for buried pipes subjected to a strongearthquake. This can be used as a basis for evaluating the level of strengthening orincreased redundancy needed by existing facilities to improve their response duringseismic events. So this covers design criteria for wave propagation, fault crossing andpermanent ground deformation (PGD) due to liquefaction, lateral spreading, etc.

This analysis and design criteria require the following engineering information.

Pipeline information

a)

Pipe geometry (diameter, thickness);b) Type of joint;

c) Stress-strain relationship of pipe material;

d) Pipeline function and its post seismic performance requirement;

e) External pipe coating specification;

f) Operating pressure in the pipe;

g) Operational and installation temperature;

h) Pipeline alignment detail (plan, profile location of fittings, etc); and

i) Reduced strain limit for existing pipelines.

Site information


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a) Burial depth of the pipeline;

b) Basic soil properties (unit weight, cohesion, internal friction angle and in situdensity).

c)

Properties of backfill soil in the trench;

d) Depth of water table; and

Seismic hazard information

a) Expected amount of seismic ground motion at the site;

b) Expected amount and pattern of permanent ground deformation and its spatialextent;

c) Length of pipeline exposed to permanent ground deformation;

d) Active fault locations; expected magnitude of fault displacement, and orientationof pipeline with respect to direction of fault movement.

The seismic safety evaluation of a continuous oil pipeline as follows:

Location 01:

The continuous buried pipeline is designed to carry natural gas at a pressure of 9.3MPa.

The pipe is of API X-60 grade with 30-in (0.762m) diameter (D) and 0.0064 m wallthickness (t). The installation temperature and operating temperature of the pipeline are300 C and 650 C respectively. The pipeline is buried at 1.5m of soil cover. Poisson’s ratioand coefficient of thermal expansion of the pipe material can be considered as 0.3 and12 x 10-6 respectively. This pipeline is checked for four cases they are

Case I: Permanent ground displacement (PGD)

Case II: Buoyancy due to liquefaction

Case III: Fault crossing

Case IV: Seismic wave propagation

For API X-60 Grade pipe:

Yield stress of pipe material = σy = 413 MPa

Ramberg-Osgood parameters n = 10 and r =12.


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Pipe strain due to internal pressure is calculated as follows

The longitudinal stress induced in the pipe due to internal pressure will be

2t

PDµ=S p =

0.00642

0.30.7629300000

×

××

=166.09 x 106 N/m2 = 166.09MPa

Using Ramberg-Osgood’s stress-strain relationship the longitudinal strain in the pipewill be

r

y

p p

pσ

S

r +1

n+1

E

S=ε

=

×

×

×

× 12

6

6

11

6

1041310166.1

12+110+1

10210166.1

= 0.0008305 = 0.08305% (tensile)

Pipe strain due to temperature change:

The longitudinal stress induced in the pipe due to change in temperature will be

ST = Eα (T2 – T1)

= 2 x 1011

x 12 x 10-6

(65-30)

= 84 MPa


r

y

ttt

σ

S

r +1

n+1

E

S=ε

=

××

××

12

6

6

11

6

10413

1084

12+1

109+1102

1084

= 0.00042 = 0.042% (tensile)

The total strain in the continuous pipeline due to internal pressure and temperature is


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= 0.08305 + 0.042

= 0.125%.

Ignoring the strain in pipe due to installation imperfection or initial bending, the above

calculated strain can be considered as the operational strain in pipe (i.e., εoper = 0.125%).


The permanent ground deformation refers to the unrecoverable soil displacement dueto faulting, landslide, settlement or liquefaction induced lateral spreading.

Figure 11. a) Pipeline crossing parallel to the ground movement. b) Pipeline crossingtransverse to the ground movement

Here the length and width of PGD zone is 120m and 50m respectively. Soil is sandy soilwith an angle of friction (Φ) = 320 and effective unit weight of 18 kN/m3. The grounddisplacement (δl and δt) due to liquefaction can be taken as 2m.

The operational strain in pipeline = 0.125% (tensile)

Yield stress of pipe material σy = 413Ramberg-Osgood parameter (n) = 10Ramberg-Osgood parameter (r) = 12

Parallel crossing (Longitudinal PGD)


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The expected amount of permanent ground movement parallel to pipe axis = δl = 2m

The design ground movement = δl design = δl x Ip = 2 x 1.5 = 3mCase-1:The amount of ground movement (δl design) is considered to be large and the pipe strain

is controlled by length (L) of permanent ground deformation zone. The peak pipe strainis calculated as

r

y

uua

Dtσ

Lt

r +

n+

DtE

Lt =ε

2π11

2π

Wheretu = maximum axial soil force per unit length of pipe for soil condition.

The maximum axial soil resistance (tu) per unit length of pipe can be calculated as

1tan2

1δ

K +γπDH +πDcα=t 0

u

Where D = diameter of pipe = 0.762m

C = Coefficient of cohesion = 30kpa

α = Adhesion Factor

= 0.608-0.123 x 0.3 – 0.27/(0.33+1) + 0.695 /(0.33 +1)

= 0.99645

H = soil cover above the centre of the pipeline = 1.5m

Interface angle of friction between soil and pipe δ1 = f Φ

Here f = friction factor = 0.7 for smooth steel pipe

δ1 = f Φ = 0.7 x 32o = 22.4o

K0 = coefficient of soil pressure at rest= 1- sin 32o = 0.47

tu = ̟ x 0.762 x 30000 x 0.99645 + (̟ x 0.762 x 1.5 x 18000 x ((1+0.47)/2)tan22.4 o

= 91144N/m =91.144kN/m

×××××

×

×××××

× 12

611104130.00640.7622

12091144

121

101

1020.00640.7622

12091144

π ++

π =ε a

= 0.002023 = 0.2023%Case-2:The length (L) of permanent ground deformation zone is large, and the pipe strain iscontrolled by the amount of ground movement (δl design). The peak pipe strain for thiscase is calculated as


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r

y

eueua

Dtσ

Lt

r +

n+

DtE

Lt =ε

2π11

2π

WhereLe = Effective length of pipeline over which the friction force (tu) acts, which can be

calculated by the following equation.

r

y

eu2eul

designπDtσ

Lt

r +1

n

r +2

2+1

πDtE

Lt=δ

From this effective length of pipeline is calculated as Le = 100m

εa = 0.0015095

The design strain in pipe is taken as the least value between the two cases = εseismic =0.0015095

The operational strain in the pipeline = εoper = 0.00125

The total tensile strain in the pipeline = 0.0015095 + 0.00125 = 0.0027595

Total compression strain = 0.0015095 – 0.00125 = 0.0002595

The limiting strain in tension for permanent ground deformation is = 0.03

The total strain in pipe due to longitudinal strain is less than the allowable strain.

Transverse Crossing:

The expected amount of transverse permanent ground deformation (δt

) = 2m

The design transverse ground displacement = δt design = δt x Ip = 2 x 1.5 = 3m.

The maximum bending strain in the pipe is calculated as the least value of the followingtwo

A. ε b=±π Dδ

design

t

W 2

= ±̟

x 0.762 x 3 / 50 2

= ± 0.00287267

B. ε b=± P

uW

2

3π EtD2

WherePu = maximum resistance of soil in transverse direction.

The maximum transverse soil resistance per unit length of pipe is


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HDγ N+cD N=P qhchu

WhereNch = Horizontal bearing capacity factor for clay

( ) ( ) 911 32 ≤+ x

d

++ x

c

+bx+a= N ch

Wherex = H/D = 1.5/0.762 = 1.968503937

a = 6.752b = 0.065c = - 11.063d = 7.119Nch =6.752+ (0.065 x 1.96) + (-11.063/(1.96+1)2) + (7.119/(1.96+1)3)= 5.896

Nqh = Horizontal bearing capacity factor for sandy soilNqh = a + bx +cx2 + dx3 + ex4

Wherex = H/D = 1.5/0.762 = 1.968503937

a = 5.465b = 1.548c = - 0.1118d = 5.625 x 10-3

e = -1.2227 x 10-4

Hence,Nqh = 5.465 + (1.548 x 1.96) + (-0.1118 x 1.962) + (5.625 x 10-3 x 1.963) + (-1.2227 x 10-4 x1.964)

= 8.120HencePu =5.896 x 30000 x 0.762+ (8.120 x 18000 x 1.5 x 0.762)

= 301869N/m= 301.869kN/m

211

2

0.7620.00641023

50301869

×××××

×

π ±=εb

= 0.1077Hence, the maximum strain induced in the pipeline due to transverse PGD is taken as

Εseismic = ± 0.00287267 (tensile/compressive)


Total longitudinal strain in the pipe in tension 0.00287267+0.0013 = 0.004172

Total longitudinal strain in the pipe in compression = 0.00287267-0.0013 = 0.0016


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The allowable strain in tension for permanent ground deformation is = 3% = 0.03

The allowable strain in compression for steel pipe is

Εcr-c = 0.175t/R = 0.175 x 0.0064/0.381

= 0.00293

The total strain in pipe due to transverse PGD is less than the allowable strain for bothtension and compression.

Case II: Buoyancy due to liquefactionThe net upward force per unit length of pipeline can be calculated asThe extent of liquefaction Lb = 50m

( ) pipecontentsat2

b πDtγγγ4

πD=F −−

Fb = ̟ x 0.762 2/4 (18000-0)-̟ x 0.762 x 0.0064 x 78560= 7005.05N/m

It is assumed that the weight of gas flowing through pipe has negligible weight. Theunit weight of steel pipe (γpipe) is taken as 78560N/m3.The bending stress in the pipeline due to uplift force (Fb) can be calculated as

Z10

LF±=σ

2 b b

bf

WhereLb = length of pipe in buoyancy zoneZ = section modulus of pipe cross section

=( )

0.762

0.74920.762

32

44 −π

= 0.0028459m4

σbf = ± 7005.05 x 502/ (10 x 0.0028459)= 615360117N/m2

Maximum strain in pipe corresponding to the above bending stress calculated as

r

y

bf bf

σ

σ

r +1

n+1

E

σ=ε

=

××

10

611 10413

615360117

12+1

10+1

102

615360117

= 0.130705674


The total longitudinal strain in the pipe in tension = 0.130705674+ 0.0012505 = 0.1319562

The total longitudinal strain in the pipe in compression = 0.130705674- 0.0012505 =0.1294551


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The allowable strain in pipe in tension is = 3% =0.03

The allowable strain in pipe in compression is

Εcr-c = 0.175t/R = 0.175 x 0.0064/0.381

= 0.0029396

The maximum strain in the pipeline due to buoyancy effect is greater than the allowablestrain for steel pipes in tension and compression.

Case III: Fault Crossing

Here the pipeline crosses a normal slip fault with fault displacement of 1.5m and a dipangle of 350. The pipeline crosses the fault line at an angle of 400. The source to sitedistance can be considered as 20km.

The expected normal-slip fault displacement = δfn = 1.5m

Dip angle of the fault movement ψ = 350

The angle between pipeline and fault line β = 400

Component of fault displacement in the axial direction of the pipeline

δ fax=

δ fncos ψ sin β

= 1.5 cos 350 x sin 400 = 0.789811m

Component of fault displacement in transverse direction of pipeline:δ fax= δ

fncos ψ cos β = 1.5 cos 350 x cos 400 = 0.94126m

Importance factor for fault movement for pipe = Ip = 2.3

Applying importance factor,

The design fault displacement in axial direction becomes

= δfax – design = δfax x Ip = 0.789811 x 2.3 = 1.816565707m

The design fault displacement in transverse direction becomes

= δftr – design = δftr x Ip = 0.94126 x 2.3 = 2.164898707m

The average pipe strain due to fault movement in axial direction can be calculated as


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−−2

2L2

1

2L2

a

design ftr

a

design fax δ+

δ=ε

WhereLa = effective unanchored length of the pipeline in the fault zone

u

yi

at

πDt ε E = L

=2× 10

11× 0 .002× π × 0. 762× 0.0064

91144

= 67.238mOrLa =the actual length of anchorage = 120m

Hence, the anchored length to be considered is the lower the above two values. So La =67.238m

Axial strain in the pipe

×××

2

67.2382

2.164

2

1

67.2382

1.81652 +=ε

= 0.02728


Total strain in pipe in tension = 0.0306 + 0.0013 = 0.0285

The allowable strain in pipe in tension is 3% = 0.03

The total tensile strain in pipe due to fault crossing is less than the allowable strain.


The expected peak ground acceleration of the site at base rock layer = PGAr = 0.45g

For this soil Peak ground acceleration (PGA) at ground = 0.45g x Ig

= 0.45g x 0.9

= 0.405g

Converting the soil as soft and the magnitude of design basis earthquake (M) is equalsto 6.5, and distance of site from earthquake source is about 20km

PGV = 0.405 x 140 = 56.7cm/s


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Converting the soil as soft and the magnitude of design basis earthquake (M) is equalsto 6.5, and distance of site from earthquake source is about 20km

PGV = 0.405 x 140 = 56.7cm/s

Design peak ground velocity = Vg = PGV x Ip

= 56.7 x 1.5 = 85.05cm/sec =0.85m/s

Maximum axial strain in the pipe due to wave velocity can be calculated as

0.0002120002

0.85==

C α

V =ε

ε

g

a×

Maximum axial strain that can be transmitted by soil friction can be calculated as


0.0002120002

0.85==

C α

V =ε

ε

g

a×


εa=

t u λ

4 AE =91144× 1000

4× 0 .0151922× 2× 1011

= 0.00750

The calculated axial strain due to wave passage need not be larger than the straintransmitted by soil friction.


The total strain in pipe in tension = 0.00750 + 0.0013 = 0.00146


The maximum strain in pipe due to wave propagation pipe is less than the allowablestrain.


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Table 4. Maximum strains in the pipe in compression and tension in four cases

CaseMaximum strain

in pipe intension

Maximumstrain inpipe in

compression

Allowablestrain inpipe in

tension

Allowablestrain in pipe

in

compression

Safe/Unsafe

I 0.0027595 0.0002595 0.03 0.0029396 SafeII 0.131956 0.1294551 0.03 0.0029396 UnsafeIII 0.0285 -- 0.03 0.0029396 Safe

IV 0.00146 -- 0.03 0.0029396 Safe

Location 2:

The continuous buried pipeline is designed to carry natural gas at a pressure of 9.3MPa.

The pipe is of API X-60 grade with 30-in (0.762m) diameter (D) and 0.0103 m wallthickness (t). The installation temperature and operating temperature of the pipeline are300 C and 650 C respectively. The pipeline is buried at 1.5m of soil cover. Poisson’s ratioand coefficient of thermal expansion of the pipe material can be considered as 0.3 and12 x 10-6 respectively. This pipeline is checked for four cases they are



Case III: Fault crossing


For API X-60 Grade pipe:

Yield stress of pipe material = σy = 413 MPa

Ramberg-Osgood parameters n = 10 and r =12.

Pipe strain due to internal pressure is calculated as follows

The longitudinal stress induced in the pipe due to internal pressure will be

S p=

PD µ

2t = 0.01032

0.30.7629300000

×

××

=103.2 x 106 N/m2 = 103.2MPa


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r

y

p p

pσ

S

r +

n+

E

S =ε

11

=

×

×

×

× 12

6

6

11

6

10413

10103.2

12+1

10+1

102

10103.2

= 0.000516 = 0.0516% (tensile)

Pipe strain due to temperature change:

The longitudinal stress induced in the pipe due to change in temperature will be

ST = Eα (T2 – T1)

= 2 x 1011 x 12 x 10-6 (65-30)

= 84 MPa


r

y

t t

t σ

S

r +

n

+ E

S

=ε 11

=

×

×

×

× 12

6

6

11

6

10413

1084

121

1091

102

1084

++

= 0.00042 = 0.042% (tensile)

The total strain in the continuous pipeline due to internal pressure and temperature is

= 0.0516 + 0.042

= 0.0936%.

Ignoring the strain in pipe due to installation imperfection or initial bending, the abovecalculated strain can be considered as the operational strain in pipe (i.e., εoper =0.0936%).


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The permanent ground deformation refers to the unrecoverable soil displacement dueto faulting, landslide, settlement or liquefaction induced lateral spreading.

Figure 12. a) Pipeline crossing parallel to the ground movement. b) Pipeline crossingtransverse to the ground movement

Here the length and width of PGD zone is 120m and 50m respectively. Soil is sandy soilwith an angle of friction (Φ) = 320 and effective unit weight of 18 kN/m3. The grounddisplacement (δl and δt) due to liquefaction can be taken as 2m.

The operational strain in pipeline = 0.125% (tensile)

Yield stress of pipe material σy = 413Ramberg-Osgood parameter (n) = 10Ramberg-Osgood parameter (r) = 12

Parallel crossing (Longitudinal PGD)

The expected amount of permanent ground movement parallel to pipe axis = δl = 2m

The design ground movement = δl design = δl x Ip = 2 x 1.5 = 3mCase-1:The amount of ground movement (δl design) is considered to be large and the pipe strainis controlled by length (L) of permanent ground deformation zone. The peak pipe strainis calculated as


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r

y

uua

Dtσ

Lt

r +

n+

DtE

Lt =ε

2π11

2π

Wheretu = maximum axial soil force per unit length of pipe for soil condition.

The maximum axial soil resistance (tu) per unit length of pipe can be calculated as

1tan

2

1δ

K +γπDH +πDcα=t 0u

Where D = diameter of pipe = 0.762m

C = Coefficient of cohesion = 30kpa

α = Adhesion Factor

= 0.608-0.123 x 0.3 – 0.27/(0.33+1) + 0.695 /(0.33 +1)

= 0.99645

H = soil cover above the centre of the pipeline = 1.5m

Interface angle of friction between soil and pipe δ1 = f Φ

Here f = friction factor = 0.7 for smooth steel pipe

δ1 = f Φ = 0.7 x 32o = 22.4o

K0 = coefficient of soil pressure at rest= 1- sin 32o = 0.47

tu = ̟ x 0.762 x 30000 x 0.99645 + (̟ x 0.762 x 1.5 x 18000 x ((1+0.47)/2)tan22.4 o

= 91144N/m =91.144kN/m

×××××

×

×××××

× 12

611 104130.01030.7622

12091144

121

101

1020.01030.7622

12091144

π ++

π =ε a

= 0.001109 = 0.1109%Case-2:The length (L) of permanent ground deformation zone is large, and the pipe strain iscontrolled by the amount of ground movement (δl design). The peak pipe strain for thiscase is calculated as

r

y

eueua

Dtσ

Lt

r +

n+

DtE

Lt =ε

2π11

2π

WhereLe = Effective length of pipeline over which the friction force (tu) acts, which can becalculated by the following equation.


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r

y

eueul

designπDtσ

Lt

r +

n

r ++

πDtE

Lt =δ

12

21

2

From this effective length of pipeline is calculated as Le = 150m

εa = 0.0015095

The design strain in pipe is taken as the least value between the two cases = εseismic =0.001446


The total tensile strain in the pipeline = 0.001446 + 0.000936 = 0.00205

Total compression strain = 0.001446 – 0.000936 = 0.0001734

The limiting strain in tension for permanent ground deformation is = 0.03

The total strain in pipe due to longitudinal strain is less than the allowable strain.

Transverse Crossing:

The expected amount of transverse permanent ground deformation (δt) = 2m

The design transverse ground displacement = δt design = δt x Ip = 2 x 1.5 = 3m.

The maximum bending strain in the pipe is calculated as the least value of the followingtwo

a) 2W

πDδ±=ε

t

design

b

= ±̟

x 0.762 x 3 / 50 2

= ± 0.00287267

b) 2

ub

EtD

W P ±=ε3π

2

WherePu = maximum resistance of soil in transverse direction.

The maximum transverse soil resistance per unit length of pipe is

HDγ N +cD N = P qhchu

WhereNch = Horizontal bearing capacity factor for clay


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( ) ( ) 9

11 32 ≤+ x

d +

+ x

c+bx+a= N ch

Wherex = H/D = 1.5/0.762 = 1.968503937

a = 6.752b = 0.065c = - 11.063d = 7.119Nch =6.752+ (0.065 x 1.96) + (-11.063/(1.96+1)2) + (7.119/(1.96+1)3)= 5.896Nqh = Horizontal bearing capacity factor for sandy soilNqh = a + bx +cx2 + dx3 + ex4

Wherex = H/D = 1.5/0.762 = 1.968503937

a = 5.465b = 1.548c = - 0.1118d = 5.625 x 10-3

e = -1.2227 x 10-4

Hence,Nqh = 5.465 + (1.548 x 1.96) + (-0.1118 x 1.962) + (5.625 x 10-3 x 1.963) + (-1.2227 x 10-4 x1.964)

= 8.120Hence

Pu =5.896 x 30000 x 0.762+ (8.120 x 18000 x 1.5 x 0.762)= 301869N/m

= 301.869kN/m

εb=±

301869× 502

3× π × 2× 1011× 0.0103× 0.762

2

= 0.06694

Hence, the maximum strain induced in the pipeline due to transverse PGD is taken as

Εseismic = ± 0.00287267 (tensile/compressive)


Total longitudinal strain in the pipe in tension 0.00287267+0.000936= 0.0038

Total longitudinal strain in the pipe in compression = 0.00287267-0.000936= 0.0019

The allowable strain in tension for permanent ground deformation is = 3% = 0.03

The allowable strain in compression for steel pipe is


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Εcr-c = 0.175t/R = 0.175 x 0.0103/0.381

= 0.004731

The total strain in pipe due to transverse PGD is less than the allowable strain for bothtension and compression.


The net upward force per unit length of pipeline can be calculated asThe extent of liquefaction Lb = 50m

( ) pipecontent sat 2

b πDtγγγπD

= F −−4

Fb = ̟ x 0.762 2/4 (18000-0)-̟ x 0.762 x 0.0103 x 78560= 6271.60N/m

It is assumed that the weight of gas flowing through pipe has negligible weight. Theunit weight of steel pipe (γpipe) is taken as 78560N/m3.

The bending stress in the pipeline due to uplift force (Fb) can be calculated as

Z

L F ±=σ bbbf

10

2

WhereLb = length of pipe in buoyancy zoneZ = section modulus of pipe cross section

=π

32

0.7624− 0.7414

4

0.762

= 0.0045101m4

σbf = ± 7005.05 x 502/ (10 x 0.0045101)=347640990N/m2

Maximum strain in pipe corresponding to the above bending stress calculated as

r

y

bf bf

σ

σ

r +

n+

E

σ =ε

11

=

××

10

611 10413

347640990

12+1

10+1

102

347640990

= 0.001976968


The total longitudinal strain in the pipe in tension = 0.001976968+ 0.000936= 0.002913

The total longitudinal strain in the pipe in compression = 0.001976968- 0.000936=0.001041


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The allowable strain in pipe in tension is = 3% =0.03

The allowable strain in pipe in compression is

Εcr-c = 0.175t/R = 0.175 x 0.0103/0.381

= 0.004731

The maximum strain in the pipeline due to buoyancy effect is greater than the allowablestrain for steel pipes in tension and compression.

Case III: Fault Crossing

Here the pipeline crosses a normal slip fault with fault displacement of 1.5m and a dipangle of 350. The pipeline crosses the fault line at an angle of 400. The source to sitedistance can be considered as 20km.

The expected normal-slip fault displacement = δfn = 1.5m

Dip angle of the fault movement ψ = 350

The angle between pipeline and fault line β = 400

Component of fault displacement in the axial direction of the pipeline

δ fax=

δ fncos ψ sin β

= 1.5 cos 350 x sin 400 = 0.789811m

Component of fault displacement in transverse direction of pipeline:δ fax= δ

fncos ψ cos β = 1.5 cos 350 x cos 400 = 0.94126m

Importance factor for fault movement for pipe = Ip = 2.3

Applying importance factor,

The design fault displacement in axial direction becomes

= δfax – design = δfax x Ip = 0.789811 x 2.3 = 1.816565707m

The design fault displacement in transverse direction becomes

= δftr – design = δftr x Ip = 0.94126 x 2.3 = 2.164898707m

The average pipe strain due to fault movement in axial direction can be calculated as


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−−2

2L2

1

2L2

a

design ftr

a

design fax δ+

δ=ε

WhereLa = effective unanchored length of the pipeline in the fault zone

La=

E i ε y π Dt

t u

=91144

0.01030.7620.002102 11 ××××× π

= 108.212m

OrLa =the actual length of anchorage = 120m

Hence, the anchored length to be considered is the lower the above two values. So La =

108.21m

Axial strain in the pipe

×××

2

108.212

2.164

2

1

108.212

1.81652 +=ε

= 0.01689

The operational strain in the pipeline = εoper =0.00094

Total strain in pipe in tension = 0.01689+ 0.00094= 0.0178


The total tensile strain in pipe due to fault crossing is less than the allowable strain.


The expected peak ground acceleration of the site at base rock layer = PGAr = 0.45g

For this soil Peak ground acceleration (PGA) at ground = 0.45g x Ig

= 0.45g x 0.9

= 0.405gConverting the soil as soft and the magnitude of design basis earthquake (M) is equalsto 6.5, and distance of site from earthquake source is about 20km

PGV = 0.405 x 140 = 56.7cm/s

Design peak ground velocity = Vg = PGV x Ip

= 56.7 x 1.5 = 85.05cm/sec =0.85m/s


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0.0002120002

0.85==

C α

V =ε

ε

g

a×


111020.02432384

100091144

4 ×××

×=

E

λt =ε ua

= 0.00468

The calculated axial strain due to wave passage need not be larger than the straintransmitted by soil friction.


The total strain in pipe in tension = 0.00468 + 0.00094= 0.00146


The maximum strain in pipe due to wave propagation pipe is less than the allowablestrain.

Table 5. Maximum strains in the pipe in compression and tension in four cases

CaseMaximum strain

in pipe intension

Buried Pipelines

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