Ptc 2016 Psarropoulos

7/25/2019 Ptc 2016 Psarropoulos

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A smart decision-support GIS-based tool for the optimization of pipeline routingtaking into consideration the potential geohazards

by

Prodromos N. PSARROPOULOS1, Stefanos TSOUGRANIS2,Andreas A. ANTONIOU

3

National Technical University, Athens, Greece

1Structural & Geotechnical Engineer, M.Sc., Ph.D.

2Surveying Engineer3

Geotechnical Engineer, Ph.D.

ABSTRACT

Many onshore and offshore oil and gas pipelines that will be constructed in the futuremay face various challenges related to the terrain or the seabed and the potentialgeohazards. Undoubtedly, in areas that are characterized by moderate or highseismicity, such as south-east Europe, north Africa, Middle East, etc., these challenges

may be greater. The experience from the past worldwide has shown that the qualitativeand especially the quantitative assessment of various geohazards, such as slopeinstabilities, active faults, soil liquefaction phenomena, is a key issue that may dominatethe routing, the design, and the construction of an onshore or offshore pipeline. On theother hand, it is evident that, the later the problematic areas are identified, the more theproblems may derive during the phases of design and/or construction. The currentpaper, after a short description of the main geohazards, describes a smart decision-support tool that has recently been developed by the authors in a geographicinformation system (GIS) for (a) the quantitative assessment of various geohazardsalong a pipeline route (i.e. the identification of the "problematic areas") and (b) theconsequent optimization of the pipeline routing. The tool may achieve the optimum

routing, taking into consideration various criteria apart from the geohazards, such asdistance minimization, avoidance of critical areas, land use, environmental constrains,etc. The tool has been verified through three case studies in south-east Europe, twoonshore pipelines and one offshore pipeline. The results demonstrate the capability ofthe tool to manipulate, analyze, and manage all the available spatial data that aredirectly or indirectly related to geohazards (i.e. topographical, geological, geotechnicaland seismological data) and to support the geoscientists and the pipeline engineers toavoid all the problematic areas as soon as possible.


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1. INTRODUCTION

Modern society demands increasing availability and reliability of energy and watersupply, together with improved environmental standards, all making for substantialchallenges. Regarding the oil & gas industry, major onshore or offshore pipelines willtraverse remote regions with extreme terrain or seabed. Many pipeline projects, existing

or planned, are in mountains and deserts, tropical jungles, in permafrost, wetlands ordeep waters. Each of these natural environments is associated with a range ofgeohazards. The term "geohazard" is used to describe any geological, hydro-geologicalor geomorphologic event or process that poses an immediate or potential risk that maylead to damage or uncontrolled risk, while the main geohazards may include landslides,soil erosion, karst, and/or river migration. In parallel, many guidelines and normsworldwide, recognize that the terrain or seabed, the soil types, and the geohazardstraversed by the pipelines are key factors to consider in the design, construction,operation and maintenance of a pipeline project.

Evidently, the identification of the geohazards during the very early stages of thepipeline design and the subsequent avoidance of the problematic areas is the optimumsolution. Nevertheless, since pipelines are usually long structures all geo-hazardousareas cannot be avoided. As shown in Figure 1a, any structure may be distressed byexternal loading, and/or induced permanent ground deformations (PGDs). Although thepipeline response and distress is dominated by the operational loading (i.e. gravity,internal and external pressures, and differences of the temperature), any PGDs mayalter substantially the pipeline strain levels, making thus the pipeline analysis anddesign a complicated problem of soil-structure interaction. Under this perspective, theterm "effective treatment" may have two meanings. From a geotechnical point of view,the treatment should aim to the elimination of the expected PGDs, while from astructural point of view, the treatment requires the pipeline verification and the increaseof its structural capacity.

Figure 1a. Sketch showing the main types of structural distress due to(a) external loading and/or (b) induced PGDs at the foundation level.


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Nevertheless, in areas that are characterized by moderate or high seismicity (and theinterrelated volcanism), earthquake-related geohazards may be present as well. Asshown in Figure 1b, the main earthquake-related geohazards are the strong groundmotion (or the seismic wave loading in the case of a buried pipeline) and mainly thePGDs due to active fault ruptures, soil liquefaction phenomena, and/or earthquake-

triggered slope instabilities. Note that strong ground motion and active fault ruptures aredirect threats to any pipeline, while soil liquefaction phenomena (i.e. pore pressurebuild-up, vertical settlements and/or later spreading) and slope instabilities are regardedas indirect threats to a pipeline as they are actually ground failures due to the strongground motion.

Figure 1b. Sketch showing the main earthquake-related geohazards (i.e. strong groundmotion, active-fault rupture, soil liquefaction phenomena and slope instabilities).

Figure 2 shows case histories of damaged pipelines in areas that are characterized byhigh seismicity (such as Turkey, Taiwan, USA, Japan), indicating that pipelines, mainly

the buried ones, are sensitive to earthquake-related geohazards and the consequentPGDs.

Figure 3 demonstrates the existing pipeline network in Europe versus the seismichazard in terms of peak ground acceleration at the rock outcrop or at the bedrock. It isevident that in north Europe, where plenty of onshore and offshore pipelines havealready been constructed, the seismic hazard is very low, while on the contrary, theseismic hazard is rather high in South Europe, where many new onshore and offshorepipelines are expected to transfer in the near future most of the hydrocarbons of north

Africa, Middle East, central Asia and Mediterranean Sea to central and north Europe.

As the occurrence of the design earthquake is an extreme phenomenon that is

expected to shake a wide area and it has a certain probability of occurrence dependingon the lifetime of the pipeline project (e.g. 50 years), the earthquake-related geohazardscannot be identified at an early stage of the design when the available data are ratherlimited, and therefore the geoscientists are capable to identify only qualitatively thepotentially problematic areas. In many cases where the avoidance of a potentiallyproblematic area is not feasible, the quantitative assessment and effective treatment ofan earthquake-related geohazard is a demanding and challenging issue directly relatedto the pipeline integrity.

hard rock

active - fault

rupture

stiff soil layers

lake

or sea

soft soil layers

slope

instabilitysoil

liquefaction

focus

seismic waves


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Figure 2. Case histories of damaged pipelines due to fault crossings and soilliquefaction during earthquakes: (a) 1999 Kocaeli, Turkey, (b) 1999 ChiChi, Taiwan, (c)

1971 San Fernando, USA, (d) 1993 Nansei-Oki, Japan.

Figure 3. The existing pipeline network in Europe versus the seismic hazard in terms ofpeak ground acceleration at the rock outcrop or at the bedrock.

ba

c d


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In parallel, according to the modern seismic philosophy and the related concept ofstrain-based design, that try to keep a balance between safety and economy, repairabledamages to a pipeline (i.e. exceedance of the yield strain) may be allowed or accepted,provided that the non-failure requirement has been fulfilled (i.e. non exceedance of thefailure strain). Obviously, the aforementioned are valid only in the cases of onshore or

shallow-water offshore pipelines, and not in the case of a deep water offshore pipelinewhere the repair of damages is rather impossible and therefore the exceedance of yieldstrain is unacceptable. Nevertheless, it has to be emphasized that, if the pipeline owner/ operator prefers conservatism to avoid the potential repairable damages and thesubsequent interruption of supply in the case of design earthquake, the treatment ofearthquake-related geohazards may increase substantially the construction time andcost.

Based to the aforementioned, it becomes evident that, the later the problematic areasare identified, the more the problems may derive during the phases of design and/orconstruction. The current paper, after a short description of the main geohazards,

describes a smart decision-support tool that has recently been developed by theauthors in a geographic information system (GIS) for (a) the quantitative assessment ofvarious geohazards along a pipeline route (i.e. the identification of the "problematicareas") and (b) the consequent optimization of the pipeline routing. The tool mayachieve the optimum routing, taking into consideration various criteria apart from thegeohazards, such as distance minimization, avoidance of critical areas, land use,environmental constrains, etc. The tool has been verified through three case studies insouth-east Europe, two onshore pipelines and one offshore pipeline. The resultsdemonstrate the capability of the tool to manipulate, analyze, and manage all theavailable spatial data that are directly or indirectly related to geohazards (i.e.topographical, geological, geotechnical and seismological data) and to support thegeoscientists and the pipeline engineers to avoid all the problematic areas as soon aspossible.

2. PIPELINE ROUTING AND GEOHAZARDS

Before the presentation of the smart tool, the need of determining the basic criteria ofthe optimum pipeline routing is evident. As described in IPLOCA (2013), the routeselection process described below is a typical approach of a pipeline routing betweenthe known start and end points and any intermediate off take points. A description

covering all potential options would be impossible since every pipeline routing selectionprocess is not similar to any other because of differences in location, land use, terrain,infrastructure, local permits and regulations, environment, and archeology. Furthermore,each route selection phase will depend on the project schedule. It is entirelyconceivable to complete and approve the final route in the project planning phase (i.e.FEED phase), whilst other projects may not do so until the project execution phase (i.e.detailed design phase). The final route selected must be safe, environmentallyacceptable, economical and practical.


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A pipeline route is a pivotal piece of information upon which the pipeline engineeringdepends. The route will define the pipeline size, terrain, soils, and engineering analysisrequirements. Engineering assessment based upon an agreed alignment selectioncriteria is an important part of a linear project. To be able to reach the best constructionline and optimize its components, the following phases should be studied in the given

order: Corridor

Defining route

Alignment

Construction line selection

The detailed pipeline route selection is preceded by defining a broad area of searchbetween the two fixed start and end points. That is, possible pipeline corridors. Theroute can then be filtered with consideration of public safety, pipeline integrity,environmental impact, consequences of escape of fluid, and based on social, economic,technical environmental grounds, constructability, land ownership, access, regulatory

requirements and cost. Economic, technical, environmental and safety considerationsshould be the primary factors governing the choice of pipeline routes. The shortest routemight not be the most suitable, and physical obstacles, environmental constraints andother factors, such as locations of intermediate off take points to end users along thepipeline route should be considered. Off take points may dictate mainline routing so asto minimize the need or impact of the off take lines or spurs. It should be noted thatmany route constraints will have technical solutions, and each will have an associatedcost.

Pipeline routing is an iterative process, which starts with a wide corridor of interest andthen narrows down to a more defined route at each design stage as more data is

acquired, to a final right of way (ROW). Initially, a number of alternative corridors withwidths up to 10 km wide are reviewed. Typically, the route alignment steps can bedescribed as shown below (see Figure 4). Each project will have its own specificcorridor-narrowing process depending on project size and location. Pipeline corridorsshould initially be selected to avoid key constraints. The route can then be furtherrefined through an iterative process, involving consultation with stakeholders andlandowners and a review of the criteria of environmental impact assessment, to avoidadditional identified constraints. The ultimate aim is to achieve an economically andenvironmentally-feasible route for construction.


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Figure 4. Narrowing down of pipeline corridor during project stages (after IPLOCA 2013)

As shown in Figure 4, the routing activities within project phases are presented below:

Route Corridor options [FEL 1, Appraise] : Involves the initial desk-top studies (e.g.topographical and geological maps) to identify route corridor options taking into accountknown key environmental and cultural sensitivities.

Route Selection [FEL 2, Select] : The desk study and visual appraisal, making use of allinformation available within the public domain, that should precede the adoption of aprovisional route within the selected route corridor. The included information regard

geological, archaeological and environmental features.Route investigation and consultation [FEL 3, Define, FEED]: This stage involvesgathering more detailed information, highlighting and mapping constraints within theroute corridor so as to assist in the selection of a preferred final route. This allows theproject to proceed onto the next stage of negotiations. All the constraints and potentialplanning problems that could affect the pipeline (e.g. timing or method of construction)should now be addressed and recorded. A traffic management plan should beproduced.


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Design and approval of final route [Project Execution Phase, detailed design] : This isthe final phase to define the best line and its components. Local planning authority andstatutory approvals, and landowner/tenant agreements, should now be finalized. Theroute of the pipeline should be identified by a locating system such as markers placedalong the route. Valve locations, AGI locations, river crossings, and geo-hazardous area

crossings should be investigated in detail, and readied for construction. The physicalbuilding and commissioning of the pipeline should now be able to commence inaccordance with the design criteria.

The geohazards under static conditions along the pipeline route define the "problematicareas" from a geotechnical point of view, where the PGDs and the consequent pipelinedistress will examine their "criticality" from a structural point of view. Thus, geohazardsunder static conditions should be identified at a very early stage (e.g. before FEEDphase) and they may dominate the pipeline routing.

Nevertheless, in areas characterized by moderate or high seismicity the geohazard

assessment requires the identification of all the hazards that are in some way related tothe seismic activity. In the case of a moderate or strong earthquake, the varying (both intime and space) seismic motion at the ground surface may impose additional distress tothe pipelines, which is usually described by the term seismic wave loading.Nevertheless, a seismic event may also aggravate the aforementioned gravity-relatedgeohazards by triggering a slope instability (such as a landslide or a rockfall) and/ormay cause additional geohazards to the pipeline (such as the rupture of an active faultor soil liquefaction phenomena). It has to be noted that the PGDs that may be causedby a fault rupture, soil liquefaction phenomena, and/or earthquake-triggered slopeinstabilities (i.e. pre-existing landslides or first-time failures) are of great importance inthe seismic design of a pipeline since they are regarded in general as a more severeloading than seismic wave loading. In the case of "earthquake-related geohazards"along the pipeline route, "potentially problematic areas" should be defined at an earlystage of the design, while these areas should be examined in the FEED phase (whenmore input data are available) in order to examine their possibility to become"problematic areas" in terms of PGDs or even "critical areas" in terms of pipeline strain.

Based on the aforementioned, Figure 5 summarizes the options for the optimum designof gas transmission projects (i.e. pipelines and compressor stations) against groundmovements. For the time being, the newly developed smart tool is capable to define the"problematic areas" and the "potentially problematic areas" (through the quantitativeassessment of safety factors) and to propose either the avoidance of these areas or theminimization of the pipeline crossings with them.

Nevertheless, the geohazard of slope instability has some peculiarities for variousreasons. Experienced geoscientists, judging from the prevailing topographical andgeological conditions, may identify a pre-existing landslide and/or estimate qualitativelythe risk of slope instability under static conditions, but, since geoscientists are ratherincapable to estimate realistically the impact of a moderate or a strong earthquake to


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the aforementioned risk (especially to a slope regarded as stable under staticconditions), they should rely on the modern seismic norms which require:

Figure 5. Flowchart showing the optimum design of gas transmission projects (i.e.pipelines and compressor stations) against ground movements.

a) the quantitative assessment of seismic slope instability potential (i.e. analyses inorder to estimate the anticipated safety factors of slope stability and the PGDs forthe pre-existing and the first-time failures), and

b) the consequent pipeline verifications (i.e. soil-structure interaction analyses in orderto estimate the anticipated pipeline strain levels).

More specifically, according to EN1998 Part 4, that refers to the seismic design ofonshore pipelines:

Buried pipelines crossing areas where soil failures or concentrated distortions arepossible, like lateral spreading, liquefaction, landslides and fault movements, shall bedesigned to resist these phenomena.

The segment of the pipeline deformed by the displacement of the ground caused by alandslide shall be verified not to exceed the available ductility of the material in tensionand not to buckle locally or globally in compression.The seismic design of buried pipeline systems shall take into account the permanentdeformations induced by earthquakes (such as seismic fault displacements, landslides,ground displacements induced by liquefaction)


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Based on available data and experience, reasoned assumptions should be used todefine a model for the hazard of permanent deformations.

The possibility of such phenomena (i.e. earthquake-induced ground movements)occurring at given sites shall be established and appropriate models shall be defined

(see EN1998Part 5)"

According to EN1998Part 5, that refers to the assessment of seismic slope instability:

A verification of ground stability shall be carried out for structures to be erected on ornear natural or artificial slopes, in order to ensure that the safety and/or serviceability ofthe structures is preserved under the design earthquake.

The response of ground slopes to the design earthquake shall be calculated either bymeans of established methods of dynamic analysis (such as finite elements or rigidblock models) or by simplified pseudo-static methods.

3. DESCRIPTION OF THE MODEL

After describing the physical framework of the problem that the tool aspires to solve, it isimportant to focus on the new GIS model and the software it was developed on.Specifically, the software used on making this model is ArcMap v.10.2.2, a part ofESRI's ArcGIS programme suite.

Geographic Information Systems (GIS) are scientific and technological tools that allowthe integration of data from different sources into a central database (geodatabase)from which they are formed and analyzed based on their spatial component. In thegeneral sense, the term describes any information system that integrates, stores,

processes, analyzes, distributes and displays geographic information. Their main aim isto understand the relationship between theoretically unconnected, data and patternsand trends are presented to them.

A GIS can relate, as mentioned earlier, unrelated information using as variable capital -key (key index variable) location. Locations or areas on earth spacetime can berecorded as dates and times of occurrence and / or as a set of three dimensionalcoordinates x, y and z, which represent the longitude, latitude and, usually geometric,height respectively. All reports of spatiotemporal location and extent of land should,ideally, be able to relate to each other and finally a "real" physical location or area. Thisbasic feature of GIS has begun to open new ground in many areas of scientific research

and makes it necessary to processes where spacetime plays an important role.Their main feature, however, is that these spatial data are associated with thosedescriptive data. This connectivity provides a more detailed view of spatial data, butalso a spatial substance of the descriptive data. The technology used for this operationis based on object-oriented data models, where both descriptive and spatial data aremerged into objects which model others with physical substance (e.g. Category ="street", Name = "St. Johns street" Geometry = "[X1, Y1], [X2, Y2] ..." Width = "20meters").


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The vast majority of the raw data in a current GIS are represented digitally, through thecollection using digital space surveying methods (Tracking Systems, Global Positioning/ GPS, Remote Sensing) or digitizing analog data (printed maps, etc.). Computersrepresent data in the form of binary digits 0 and 1, so any given point on the Earth'ssurface is eventually reduced by the GIS system to a combination of 0 and 1. In

particular, the data represent real entities (e.g., roads, land use, topography, trees,rivers, etc.), with the digital data to determine the final mixture. The real objects can bedivided into two categories, which are the two fundamental ways of geographicalrepresentation: discrete objects and continuous fields. The consideration of discreteobjects (e.g. a building) represents the geographical world in the form of objects withdefined boundaries in an otherwise empty space. Rather, the vision of continuous field(e.g. amount of rainfall, topography, etc.) represents the real world with a finite numberof variables, each of which is determined by the value in each possible position(Longley et al., 2010). The continuous field and the discrete objects, however, are twoconceptual considerations of geographic phenomena and do not solve theaforementioned issue of digital representation. The problem is that both considerations

contain infinite amount of information in the case of variable definition per each point,which cannot be represented due to technical limitations of computers. The twomethods used to limit the geographical phenomena in forms that can be encoded oncomputer data bases are mosaic (single raster) and vector representation (Figure 6a).Theoretically, both can be used to encode both the continuous and discrete entities, inpractice, however, the mosaic representation is associated with continuous fields andthe vector with the discrete objects.

Figure 6a. The difference of representation of real objects in the vector and rasterrepresentation respectively is evident.

The vector data model representation, as mentioned above, is based on the assumptionthat the earth's surface is composed of discrete objects such as trees, rivers, lakes, etc.These objects can be represented as a point, linear and polygonal bodies with well-defined boundaries. The boundaries of these entities are defined by pairs of coordinates

(x, y), both of which are mentioned in one place in the real world (Figure 7). Specifically: Point entities are defined by a pair of coordinates (x, y).

Linear entities defined as two or more coordinate pairs (x, y).

The polygonal entities defined by lines close to form the polygon.

In each vector representation model each entity is assigned a unique numericalidentifier value which is stored as a record in a list of attributes (attribute table). In the


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mosaic data representation Earth is represented as a grid of cells of equal size, to whichthey are assigned properties features. A single cell represents a portion of land to sizeand is the basic model parser (Figure 6b). Unlike the vector data model, wherein thecoordinate pairs (x, y) are used to define the shape and location of entities in the mosaicdata model only a pair (x, y) is substantially present, called the pair of origin and defines

the position of each cell. This pair can be referred to the center of the cell or one of itsedges. Also, each cell is assigned a numerical value, which may represent any kind ofinformation about a specific location such as altitude measurement (Figure 6b) or acode number identifying the type of vegetation.

Figure 6b: Pairs of Coordinates in a vector data model (left) and pairs of coordinates ina raster data model (right).

After the description of data models and their way of representation, it is appropriate tomention some basic concepts of GIS, which are key mechanisms and guidanceterminologies assist the overall view and understanding of subsequent case studies. Inparticular, as key concepts considered are:

Geographical position or location (location):A certain position on the earth's surface,defined under used geographic reference system.

Geographic reference system (geographical coordinate system):It is the geographiccoordinate system (latitude, longitude) to which they relate the data collected.

Spatial distribution:The order in which the objects, events, etc. located at the earthsurface are distributed in space.

Spatial geographical entities: It is defined geometric shapes that have a place inreality and depicted on maps in accordance with this (http://xsomaras.somweb.gr/,2013), and constitute the geographical space. They are divided into point, linear andpolygonal.

Topology: In the field of Geoinformatics (which include the GIS) means the sum of

the geometric rules that geographical information should follow, depending on itsnature. A typical example is a building polygon represented as a polygon, whoseboundaries do not coincide with those of neighboring polygons, ie avoid theirduplication.

Geodatabase or geographic database: It is a database in which to store a set ofgeographical and descriptive data, while providing the ability to edit and update.


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Table characteristics or properties (attribute table):Archives of the geodatabase thatcontains information about a set of geographic features, which are usually arrangedin tabular form (table). Each set (row) represents a single entity called record, andeach column represents an attribute of an entity, called the field. In data setsmosaics, each line of the attribute table corresponds to a specific range of cells that

have the same value. Note that the fields unique identifier number (ObjectID), area(Shape_Area) and plate length (Shape_Length) created and automatically populatedby the GIS software for vector data, while mosaics data fields unique identifiernumber (ObjectID), characteristic value and the number of alerts (Count).

Layer: The visual representation of a geographic dataset in any digital mapenvironment. Conceptually, it is a slice (slice) or a layer (stratum) geographic realityin a particular area and is approximately equivalent to a paper map (Figure 6c). In aroad map, for example, roads, national parks, political boundaries, rivers etc. can beregarded as different layers.

Figure 6c: An example of layer overlay, aiming to a realistic representation of real world.

Query:It is a user request of GIS software examining the list of characteristics basedon the specified criteria and displays those features or records that meet the criteria.

Structured Query Language (SQL): Reported as a special purpose programminglanguage SQL, is designed to manage the data in a database system (Forouzan andMosharraf, 2010). Based on formal algebra and relational calculus tuple (tuplerelational calculus), which expresses the relationship between a database data

(https://en.wikipedia.org/wiki/SQL, 2015).

After establishing what a GIS is and explaining some of its basic concepts andterminologies, the procedure of constructing the model that was used by the smart toolcan be further analyzed. Modeling real situations using GIS in order to obtainconclusions about the real world itself (GIS - Enabled Modeling), is a new andinnovative stream that is beginning to be explored and applied in many projects ofcomplex character. Having already emphasized the importance of geohazards andpresented the intricate and complicated problem of selecting and making a pipeline


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route, this paper investigates the usefulness of GIS on the definition of possibleoccurrence of geohazards areas and modeling of the path selection problem of apipeline, including the aforementioned criterion (hazardous areas).

The definition of the pipeline route was based on a multi-criteria analysis, which was,executed through creating and applying models that used the collected data. The

models are simulations of the real world, which operate with a subtract sense. At theprocess of removing from the available information excluded items are either notconsidered significant by the investigator to uncover the reality either simplify theframework within which take place the selected procedures. The models for each casestudy were constructed by using the Model Builder tool of Arcmap programme. Theirconstruction was introducing tools of the standard toolbox of ArcToolbox and supplyingthe data to the corresponding geodatabase as parametric values for their execution.Data input to a tool (input) and export results (output) this is the basic process ofmodeling, since the final form emerges as a logical sequence of such procedures: "Amodel is built by connecting processes".

Note that the models applied followed some logical steps which were:

Proper configuration of input data (vector or raster), depending on each toolsrestrictions

Definition of potentially dangerous areas through superposition of the data layers

Set start point and end of the pipeline route

Creating qualitative cost surface based on the overlay of thematic levels ofpossible occurrence of geohazards and distance costs

Ultimately making the best path based on the least total cost

4. CASE STUDIES

As mentioned before, the tool has been verified through three case studies of pipelinesin south-east Europe. The two case studies refer to onshore pipelines in west Greece,while the third refers to an offshore pipeline between Albania and Italy, in Adriatic Sea.

4.1. Case study 1: Onshore pipeline in north western Greece

The first case study refers to an onshore gas pipeline in north-western Greece (seeFigure 7). The wider area under examination is characterized by moderate to highseismicity and the main geohazard is the potential slope instabilities under static andseismic conditions. Since in this case study the pipeline routing has been finalized, the

smart tool is not used for route optimization, but for the quantitative assessment of slopeinstability and the identification of the "problematic areas". Figure 8 shows the availabletopographical information (i.e. Digital Elevation Model) and geotechnical information (i.e.soil categories and mechanical properties) that have been used as input data for thesmart tool. Figure 9 shows the results of the smart tool in terms of (a) safety factors ofslope stability under static conditions, and (b) critical acceleration.


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Note that a pre-existing geological study had tried to identify qualitatively the "potentiallyproblematic areas" under static conditions (i.e. the slopes characterized by low stability)and a geotechnical (earthquake) engineering study that had been performed by theauthors in the past had calculated the corresponding safety factors of slope stabilityunder static and seismic conditions. In the case of static conditions, the relatively good

comparison between (a) the "potentially problematic areas" of the geological study, (b)the "problematic areas" identified by the geotechnical engineering study, and (c) the"problematic areas" predicted by the smart tool demonstrates the capability of thedeveloped tool to support the work and the engineering judgment of the geoscientists.

Figure 7. Map showing the area of the first case study (onshore pipeline in north

western Greece).

Figure 8. Input data of the first case study: (a) topographical data (i.e. Digital ElevationModel), and (b) geotechnical data (i.e. soil categories and mechanical properties).


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Figure 9. Results of the smart tool for the first case study:(a) static safety factors, and (b) critical acceleration.

4.2. Case study 2: Onshore pipeline in the town of Preveza, western Greece

The second case study refers to an onshore pipeline that could hypothetically cross thesmall town of Preveza, western Greece (see Figure 10). In this case study the smarttool was utilized in order to obtain the optimum pipeline routing. Apart from the criteria ofdistance minimization and avoidance of certain areas (i.e. urban areas, archeologicalsites, and lakes), the smart tool may identify and avoid the problematic areas in terms ofgeohazards taking into account the potential slope instabilities and the hazard of soilliquefaction. Figures 11, 12 and 13 show the input data of this case study, while Figure14 shows the results of the optimum pipeline routing depending on the desiredcombination of the weights of each criterion.

Figure 10. Map showing the area of the second case study (onshore pipeline in thetown of Preveza, western Greece).


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Figure 11. Topographical data of the second case study (i.e. Digital Elevation Model).

Figure 12. Input data of the second case study: (a) land use (i.e. urban areas,archeological sites) and environmental constraints (i.e. lakes), and (b) soil categories.

Figure 13. Input data of the second case study: (a) ground water level, and (b)acceleration levels according to a microzonation study.


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Figure 14. Pipeline route optimization depending on the weights for the four criteria.Four different cases have been examined: (a) 25% to all criteria, (b) 40% to the criterion

of minimum distance and 20% to all the rest criteria, (c) 40% to the criterion ofavoidance of certain areas, 30% to the criterion of the avoidance of liquefiable areas,

and 15% to all the rest criteria, (d) 30% to the criterion of minimum distance and to thecriterion of avoidance of certain areas and 20% to all the rest criteria.

4.3. Case study 3: Offshore pipeline in the Adriatic Sea

The third case study refers to an offshore gas pipeline that could connect Albania andItaly, in the Adriatic Sea (see Figure 15). In this case study the smart tool was utilized inorder to obtain the optimum pipeline routing. The smart tool may identify, avoid orminimize the length of the pipeline crossings with the problematic areas in terms ofgeohazards taking into account the potential active faults and the hazard of soilliquefaction. Figures 16 show the input data of this case study, while Figure 17 showsthe results of the optimum pipeline routing depending on the desired combination of theweights of each criterion.

a b

dc


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Figure 15. Map showing the area of the third case study (offshore gas pipeline in the

Adriatic Sea).

Figure 16. Input data of the third case study: (a) areas of high concentration ofsediments, (b) potentially active faults, and (c) acceleration levels.

Figure 17. Pipeline route optimization depending on the weights for the two criteria.Two cases have been examined: (a) 30% to the criterion of avoidance of liquefiable

areas and 70% to the criterion of avoidance of active faults, (b) 70% to the criterion ofavoidance of liquefiable areas and 30% to the criterion of avoidance of active faults.


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5. CONCLUSIONS & FUTURE IMPROVEMENTS

The current study describes a smart decision-support GIS-based tool that has beendeveloped by the authors for the optimization of pipeline routing taking intoconsideration the potential geohazards, with special emphasis to the earthquake-related

geohazards (i.e. active fault ruptures, soil liquefaction phenomena and slopeinstabilities). The tool may achieve the optimum pipeline routing, taking intoconsideration various criteria apart from the geohazards, such as distance minimization,avoidance of critical areas, land use, environmental constrains, etc. The tool has beenverified through three case studies in south-east Europe, two onshore pipelines and oneoffshore pipeline. The results demonstrate the capability of the tool to manipulate,analyze, and manage all the available spatial data that are directly or indirectly relatedto geohazards (i.e. topographical, geological, geotechnical and seismological data) andto support the geoscientists and the pipeline engineers to avoid all the problematicareas.

Since the developed tool is based on analytical equations that estimate quantitatively,but empirically, the factors of safety for various geohazards (and thus to identify theproblematic areas), the smart tool is currently being improved with an automaticexternal communication with various geotechnical codes / programs capable to assessmore realistically the various geohazards (e.g. slope instability). In that case thecommunication includes the automatic generation of 2-D (or even 3-D) models atcertain locations of the terrain (or the seabed in the case of offshore pipelines) and therealistic assessment of the safety factors (and the potential PGDs).

As mentioned before, the qualitative assessment of geohazards may define the extendof the "potentially problematic areas", while the quantitative assessment may lead to thedeterministic identification of the "problematic areas". Nevertheless, since the structuralcapacity of the pipeline is an important factor that should be taken into consideration inorder to decide whether a "problematic area" is a "critical area" or not, an additionalpotential improvement of the smart tool would be the automatic external communicationwith various structural codes / programs. In that case the communication includes theautomatic generation of 2-D (or even 3-D) models of the pipeline in order to assessrealistically the anticipated soil-pipeline interaction and the pipeline distress (e.g.strains).

Finally, the tool could be upgraded in order to be utilized during the operation of apipeline project in two different ways. The first is to upgrade the tool as a DynamicBuilding Information Model (DBIM). In this way, during the life-time of a pipeline anychange of the initial information / data (i.e. topographical, geotechnical, seismological,etc.) would be incorporated into the tool (manually or even automatically) and a re-evaluation of the critical areas would be performed. The second upgrade could be thepotential connection of the tool with a remote field-monitoring system. The systemshould be installed at all critical areas (initially identified and updated) that are remotewith limited accessibility, and it could include the following:


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a) Accelerometers for the recording of the triggering mechanism (i.e. the ground motionat the ground surface).

b) Inclinometers, topographical instrumentation, etc. to measure the PGDs caused byvarious geohazards (e.g. slope instabilities, soil liquefaction, fault rupture).

c) Early warning systems connected with strain gauges, fibre optics, etc., to measure

the pipeline strain levels and react as soon as possible.

6. REFERENCES

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Forouzan, B. and Mosharraf, F. (2010), Foundations of Computer Science, London:Cengage Learning Inc.

Gazetas, G., Kallou, P. and Psarropoulos, P. (2001), Topography and Soil Effects inthe Ms 5.9 Parnitha (Athens) Earthquake: The Case of Adames, Natural Hazards,Volume 27, p. 133-169.

IPLOCA (2013), Onshore Pipelines - The Road to Success.

Kramer, S. (1996), Geotechnical Earthquake Engineering, Upper Saddle River: PrenticeHall.

Longley P., Goodchild M., Maguire D.J., Rhind D.W., (2010), Geographic InformationSystems and Science (GIS), England: John Wiley & Sons Ltd.

Moness, R. (2008), Pipeline GeoEnvironmental Design and Geohazard Management,New York: ASME.

Nyman, D., Lee E.M., Audibert J.M.E. (2008), Mitigating Geohazards for InternationalPipeline Projects: Challenges and Lessons Learned, 7thInternational PipelineConference, Calgary, Alberta, Canada.

O Rourke, Liu, J. (2012), Seismic Design of Buried and Offshore Pipelines, ew York:MCEER.

Ortigao, J., et al. (2004), Handbook of Slope Stabilization, New York: SpringerVerlagBerlin Heidelberg GmbH.

Psarropoulos P.N., Antoniou A.A. Designing onshore high-pressure gas pipelinesagainst the geohazard of earthquake-induced slope instabilities, Pipeline TechnologyJournal, ISSN 2196-4300, 66-85 (2014).

Slejko, D., et al. (1999), Seismic hazard assessment for Adria, Annals of Geophysics,Volume 42 (No.6), p. 10851105.

Somaras, . (2013), What are the geographic information systems,http://xsomaras.somweb.gr/?p=469, [accessed: 15/9/2015]

Wikipedia Project (2015), SQL: Structured Query Language,https://en.wikipedia.org/wiki/SQL, [accessed: 29/9/2015].

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Ptc 2016 Psarropoulos