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ISSN 0340-3386 - K 1252 EISSN 0340-3386 - K 1252 E VULKAN VERLAVULKAN VERLAG

International

Journal fl for Pr Piping, E, Engineering, P, Practice

Special Edition 13/2004

Special Steel Pipelines Technology

Trenchless technologies in pipelineconstruction

Dipl.-Ing. Leopold Scheuble, Karlsruhe (G)

erschienen in 3R international Special Edition 13/2002

Vulkan-Verlag GmbH, Essen

Ansprechpartner: Nico Hülsdau, Telefon 0201/82002-33, E-Mail: [email protected]

3R international 43 (2004) Special Steel Pipel ine Technology2

1. Development and significanceof pipeline constructionPipelines are a rather economical andeco-friendly way of transporting liquidand gaseous fluids, like natural gas,water, oil or district heating, coveringlong distances. Pipelines transport hugeamounts of energy safely, quickly andeconomically. This is an extremely gentleand efficient way of transportation. Highdemands on operational safety and theequipment used, as well as regularintensive checks of the operatingprocess, applying the latest techniques,assure the high safety standards of thistransportation system.

If the water supply is nationwide, watergalleries and transport lines installedunderground connect the source to thestorage and distribution spots, which areoften far away.

Pipelines transport oil and gas from theexploitation area to the plants for furtherprocessing. The products are handed onto the industrial or private user via furthertransport and distribution lines ordistribution networks.

Producing countries and pipelines forwater, crude oil and natural gas havebeen in the spotlight of geo-politicalobjectives and development at all times;economical development and growth arebased on them, as well as dependencytowards trusts and politically motivateddecisions.

Mainly decisive for the concept,construction and operation of pipelinesare not always distances and technical oroperational expenditure, but ratheramounts of delivery, consumerscontracts or, finally, political decisions.

At least in Europe, cross-nationaleconomy pacts are founded, replacingnationally orientated autarky attempts.The EU tries to cross-link producers andconsumers of oil and gas products viapan-European transportation corridors,in order to guarantee the supply fromseveral different markets.

Drivers of the global energy monopolyare the international energy groups, whoact as multinational major coorporations,either under private or governmentaldirection, depending on their politicalbackground. Surely, it is difficult toseparate the area between governmentinterventions and independent decisionsmade by the group; crude oil and naturalgas have been the lubricants of theeconomy at all times, therefore they arealso the base of development in theproducing and consuming countries.

1.1 The first pipelines – historicreflections

According to a page in the internet, in theformer times of Greek civilisation, theprobably first „pipeline“ in history wasinstalled because the Cirò, one of theoldest Italian wines, was conducteddirectly to the hulls of the ships in specialceramic pipes.

Another excursion through the history ofpipeline construction leads us to a brineline between Reichenhall and Traunstein,which is seen as the oldest pipeline,according to our present definition of theword. This line, built between 1617 and1619, had a length of 31 km andconsisted of 8.500 pipes made of wood,each 4 m long. The 238 metres of heightbetween Reichenhall and Inzell weresurmounted by water wheels of 7 metresheight and driven by water power.

In the 19th century, 1860 important waterreservoirs were found in the region oftoday’s Grampian National Park inVictoria, Australia. There, between thevalleys of Mount Williams and the SierraRanges to Stawell, the first pipeline forpotable water was built, with a length ofmore than 30 km.

Another important line was also built inthe north-west of Australia, it is thelargest drinking water line in the world.The discovery of gold near Coolgardie in1892 and Kalgoorlie in 1893 lead to theconstruction of the Golden Pipeline. 566km of pipeline altogether, made from66,000 steel pipes, 760 mm in diameter,with lengths of 8.50 metres each, wereinstalled underground from 1898 till theofficial opening in 1903. To this day,approximately 350 km of the originalLock Bar Steel Pipe are still in use.

1.2 Oil – the Black Gold

The search for the black gold becamethe main driving power for adventurers

and businessmen alike to build pipelines.Since the 15th century, kerosene forlamps was gained from oil sources belowthe ground. It was in 1848, when the firstoil well of the world was drilled in Baku,followed by the first refinery in 1859, alsoin Baku. Modern oil production reallystarted in 1872; there is only oneproduction plant in Romania which is anolder one.

Baku had developed into one of thelargest industrial cities in Russia. At theend of the 19th century, the first oil boomin Baku broke out, when the Nobels andRothschilds came in to town to challengethe Standard Oil Company of JohnRockefellers. They built the first pipelinein 1897, running from the Caspian Sea tothe Black Sea. More than half of the oilon the world markets came from Baku100 years ago.

The first oil drills in the United Stateswere carried out in 1857. The firstpipeline in the USA was built in 1865,with a length of 8 km and a daily flow rateof 250 tons. As a result, the United Statesbecame the dominating producers untilthe mid 20th century, and were almostself-sufficient at that time.

Today’s structures in the producingcountries were established the middle ofthe last century, and it was not before1967 that the first crude oil from theNorth Sea could be processed by BritishPetroleum.

In 2005, huge pipeline systems, like theBTC- Baku - Tblissi - Ceyhan with alength of 1.760 km, will start service, tosupplement the current shipments withultra large carriers for oil. Parallel to theBTC-Pipeline, the South Caucasus GasPipeline (SCP) is being installed in thesame pipeline corridor between Bakuand Erzurum (Figure 1). Large projects,like the Alaska Pipeline, the MackenzieValley Project in Canada or the pipelinefrom Siberia to Japan and China, are allin various stages of preparation atpresent.

1.3 Natural gas – a further source ofenergy

Besides the mineral oil, with its differingchemical compositions and corres-ponding exploitation and conditioningexpenditure, natural gas is steadilygaining importance as a clean energy. Inearlier times, it was flared a wasteproduct during mineral oil production,but now it is gathered along or even

PIPILINE CONSTRUCTION

Trenchless technologies in pipelineconstruction

Dipl.-Ing.Leopold ScheubleKarlsruhe (G)Tel. +49(0)721/8306048Email: [email protected]

3R international 43 (2004) Special Steel Pipel ine Technology 3

searched with separate explorationbores.

At present, large gas deposits are foundand exploited in the traditional oilproducing regions, as well as in NorthAfrica, China, Australia and in the wholePacific Region (Figure 2).

Not only the producer and consumercountries, but also the transit countriesare in the direct focus of internationaldecisions. Turkey, for instance, is alreadyseen as a turntable for oil and gas fromthe Caspian Region and the Middle East,and also for gas from Egypt. With thehelp of new installations or theconnection of already existing pipelinesystems across the Balkan, these rawmaterials are planned as a part of theEuropean supply.

The gas supply between South andNorth America, just as between Australiaand China, is managed by liquid gas

transports, but more and more also bythe construction of new lines.

More feeder lines to new industrialcentres or distribution networks inChinese towns with more than a millionof inhabitants are being installed alongtransportation lines, i. e. the 4,000 kmlong West-East Pipeline, which is alreadyin use.

1.4 The beginnings of HDD in pipelineconstruction

The exploitation, but most of all, thetransportation of oil and gas would neverhave been accomplished without thedevelopment of the vertical drillingtechnique and the trenchless installationmethods.

We have heard of drilling attemptscarried out by the Chinese as far back intime as 600 B.C.; 1420 saw the first boretrials in Europe and at the end of thesame century, Leonardo da Vincideveloped the first machine forhorizontal drilling, which could drillthrough wooden trunks to produce waterpipes.

The vertical drilling technique, however,was improved immensely by theexploration of crude oil by the end of the19th century. Then, in 1920, the firstholes in horizontal direction were drilledin the German hard coal mines, non-steered application could achievelengths of up to 200 metres into the coalstratum.

The first horizontal river crossing beneaththe Pajara River near Watsonville inCalifornia was performed with an inclinedvertical drill rig by Martin Cherrington. Inthe time following this event, thecompany carried out 36 further crossingbores beneath rivers and traffic ways

until 1979. 1979 is also the year ofconstruction for the “prototype” of ahorizontal drilling unit for near-the-surface application, with a slanted drill rigfor installing pipelines.

Halfway into the eighties, the HDDtechnology came over to Germany andEurope from the States. Meanwhile, thefurther development of the drilling andsteering technique allows drills from afew metres up to 2 kilometres.

The well-known jack & bore methodshave established themselves for shorterdistances. With the TT technology, youcan drive pipes up to 4 metres indiameter. Microtunnelling machines withfully automatic control force open exactbore paths, and the plough techniquecan also be applied for smallerdimensioned lines.

The development of trenchlesstechnologies has added furthereconomical dimensions to pipelineinstallation, and our ecology also profitsfrom these techniques. For moreinformation concerning the current stateof technology, further developments andtheir application, contact themanufacturers and suppliers ofmachines, equipment and fuels.Institutions, like IPLOCA or DCCA andthe European sister association DCA areimportant forerunners of the HDDtechnology. The relevant professionalmagazines have always been importantsources of information on the latestevents and novelties, but also theinternet portals, like Nodig-construction.com or the portals of GSTTand ISTT.

2. Utilisation of trenchlessinstallation technologiesThe determination of a pipeline courseoften follows political motivations,especially when projects are crossingseveral countries, therefore it is notalways bound to be the most economicalversion. This may certainly lead totechnical constraints, which demand acertain analysis of the alignment withfocus on the installation technologies.The application of trenchless methodsmay be technically and economicallyreasonable in just these special cases. Itmust be the in the interest of all peopleinvolved to keep costs low bymaximising the share of trenchlesstechniques.

Precise observation can be worthwhile;in pipeline construction, like in otherbranches, economic constraintsdetermine the method of action, and inmany cases, the utilisation of thetechnical possibilities of trenchlesstechnology result in shorter workingtimes coupled with a more economical


Fig. 1: Overview of the caspian pipeline nets

Fig. 2: World natural gas reserves


installation than would be possible withopen trench methods.

Already the plough technique for linediameters up to approx. 350 mm hasimmense advantages, compared to theopen trench method. The ploughtechnique is also used in shallow waterregions.

The HDD technique makes trenchlessline installation possible and isincreasingly established in pipelineconstruction and for layingtransportation lines. It is mainly used

• crossing inshore waters, rivers, canalsand irrigation systems

• crossings beneath railway tracks,streets and highways,

• avoiding damaged terrains,

• protecting flora and fauna

• landscape protection and natureconservation regions especially,

• to overcome topographic obstacles ordifficult soil structures, e. g. rocks

• wherever obstacles or particularlysensitive parameters make theapplication of open-cut or othermethods like the cable ploughtechnique, difficult or even impossible

Thus the HDD technology is gaininggrowing economical and ecologicalimportance. A more recent statementconcerning the distribution of applicationareas of HDD technique is alsointeresting (Source: Undergroundconstruction 41, June 2004, Figure 3).

Particularly the linkage of offshore withonshore plants sees the open trenchconstruction, due to its negative effects,increasingly being replaced by the HDDtechnique. The sensitive transitionregion, with shallow water zones, stripsof shore and flood protection banks, issimply undercrossed from the shorewithout disturbing flora and fauna(Figure 4).

2.1 From the idea to installation

Years before being started, manypipeline projects already exist as an ideaor even as a detailed image. Changinggeneral economic conditions, politicaldecision processes, the struggle to findan ecological route or assuring thefinancial side are common reasons forlong time delays, before the execution ofthe project may commence.

At a definite time the required measures,from preparation to commissioning, canbe carried out within a tight timeschedule (see att. Baku – Tbilisi – Cehyan(BTC) – pipeline, Figure 5).

As soon as the political starting shotgoes off and a feasability study has beencarried out, the pipeline route, which isable to meet all the requirements of theconstruction phase and later service lifebest, is chosen from all possible courses.

This choice is based on theEnvironmental and Social ImpactAssessments (ESIA), accompanied bythe Government, the general public, theNGO’s and the financial backers, like theWorld Bank, EBRD or IFC. Thistransaction is time and moneyconsuming; drawing up the documents,their layout, the public meetings,hearings and inspections take a lot oftime. The ESIA documents of the BTC


Fig. 3:HDD-Applicationrange

Fig. 4:HDD offshoreapplication

Fig. 5: BTC-Pipeline time schedule


project comprise more than 11,000pages.

All persons concerned have their ownideas and regulations; to take them allinto account or to find compensation,often on a monetary base, is animportant step in the direction ofachieving the permission andapprovability of such a project.

At this stage of the project, it is alreadypossible to minimise many technical andeconomical risks by applying trenchlesstechnologies. Some examples for thisare:

• utilising the HDD technology forcrossing sections of the bore pathwhich includes the risk of landslides toavoid destabilisation, which is to beexpected with the open cut method

• undergoing inaccessible path sectionswith long distance installation, thissaves elaborate structural measuresfor establishing access roads

• crossing natural areas worthprotecting with the help ofunderground construction methods ingreater depths: time and moneyconsuming discussions with pressuregroups are avoided, the protection ofnature can truly and constantly beguaranteed

• In an actual case, the utilisation ofprivate property and the payment ofcompensation could be avoided byapplying the HDD method.

• The installation of a line with the HDDtechnique in great depths helps toavoid a limitation of the utilisation,which would be the natural result of anopen trench installation with the usualcover of only a few metres.

All these points show clearly that it ispossible to defuse environmentallyrelevant demands and other constraintsat an early stage with the trenchlessinstallation method and to guarantee thefeasability and viability of a project.

2.2 Conceptional and aspectsenvironmental

“Throughout the pipelines planningprocess we have worked to minimisenegative impacts on the environment andsociety”. This sentence in a BTCdocument already marks theresponsibility of all parties concerned atthe stage of conception. The basiccourse for installation and operation ofthe pipeline is already set at this stage,and this course suggests the trenchlessmethod for line installation.

Therefore, a few of the maximes shall bedrawn up, following the plan andconstruction of the BTC pipeline and theSCP following the same path some timelater on.

Economical and social goals are

• combustion emissions

• no loading or offloading emissions

• zero discharge of oil or chemicals toland or surface waters

• maximising efficiency of net energyexported

• minimizing project footprint (includingRight of way (ROW),temporaryfacilities and access roads)

• no net damage to protectedecological areas or archaeologicalsites

• no creation of access routes tootherwise inaccessible areas

• restoration of habitat and hydrologicalregimes

• no loss of containment of product

• no resettlement of local population

• no permanent disruption to thelivelihood of the local population

Concrete effects of these principles canbe seen in the fact that an examination ofthe flora and fauna, above and below thecrossing area of the river, is carried outbefore river crossings are established,and the effects of construction andoperation of the pipeline is drawn up inan evaluated scale. The decision, inwhich way the pipeline installation andother measures taken duringconstruction and operation shallcommence, is based on these results.The crossing types and the manner ofconstruction, for example, are defined inthis way.

2.3 Reflections on the trenchless part

In pipeline construction, the installationof lines in populated areas is generallydone underground, still mainly applyingopen trench methods. The trenchless,closed installation part of the completebore path length may not be relevant, butit is of great importance to realise thatmany projects – particularly those withlarge crossings of any kind – could not becarried out without the trenchlessmethod at all. A dense settlement andvaluable surfaces are disturbed in veryfew places alone, emissions are reducedor occur only on a small scale and smalllimitations of use are avoided.

The following recent examples may backup these statements. But even thepopulation in apparently unproblematicregions shows increasing sensitivitytowards the effects of above-groundconstruction methods – as is madetransparent by the ESIA transactionconcerning the BTC pipeline. Thisdevelopment almost forces us to applythe underground installation techniques.

The BTC pipeline, with its total length of

1,760 km (1,091 miles), is divided into445 km in Azerbaijan, 245 km in Georgiaand 1,070 km in Turkey. Crossings in thepipeline path concern

• rivers, canals and other inshorewaters

• public roads and pathways

• railway tracks

• underground lines of all kind

• special geological features (like activefaults etc.)

As a result, Azerbaijan has 350, Georgia250 and Turkey 300 crossings beneathrailways and roads, river crossings areAzerbaijan 30, Georgia 200 and Turkeyapprox. 600. Of course this includes allinshore waters, from the rivulet to thedried out wadi to the mountain stream inflood.

In most cases, namely in less sensitiveareas of minor importance, thesecrossings are done with the open trenchmethod. Figures from the BTC section inAzerbaijan clarify the relations betweenopen and trenchless installation: besidesseven HDD- crossings, this section with445 km in length requires theperformance of 21 auger borings. Here,the pipeline is installed inside the built-inprotection pipe, in order to avoid damageto roads and railway tracks and todisturb sensitive river regions and naturalareas as little as possible.

Definitely different relations can be seenin the example of the 354 km longproduct pipeline from Stade to the DOWChemical location in Teutschenthal. Forthis steel pipe, dimensions 273x5.6/8.8mm, with PE coating, 113 pressings, 9protection steelpipe pressings and 203steered HDD drills were carried out, 24 ofthem were larger crossings of rivers andnavigation canals.

When the Alliance Gas Pipeline in NorthAmerica (length 1,900 miles, 36-inch indiameter) was installed the relations wereas follows: more than half of the roadcrossings were executed in the road boretechnique. 13 large river crossings had tobe overcome additionally, the HDDcrossing of the Peace Rivers, with 3,600foot (1039 metres), being the mostchallenging of them all; ramming andHDD technique were combined for this.Microtunnelling machines were also usedfor the project.

When comparing the Trans AlaskaPipeline System (TAPS) to the Sakhalin IIPipeline, we also get insight intointeresting figures. Both lines run throughinhospitable arctic regions, but theirmodes of construction vary.

The TAPS is an oil pipeline, 1200 mm indiameter, pressure 70 bar and 1,280 kmlong; 673 km of these run above the



ground, 602 km are built conventionallyunderground, 6 km are equipped withspecial freeze-protection devices. Morethan 900 rivers and brooks, 70 of themsignificant, were crossed by 13 pipelinebridges or open trenches of 2.3 to 4.8metres, almost 15 metres deep in themost extreme case. No HDD crossingswere performed. At the beginning of theseventies this technique seemedunsuitable for such an extreme plan;also, large rocky boulders obstruct thearea of the bore path.

Recent experience in the U.S. Arctic(ARCO Colville River Crossing) has onlynow proved the technology in Permafrostconditions. This project was executed in1997/1998 and took seasons rather thanthe single season planned. The analysisof the crossing type (Bridge, trench,HDD) used similar methodology as usedby Sakhalin Energy. HDD was chosen asbeing least expensive (at the time, basedon a single season construction.

The Sakhalin II Pipeline consists of an oiland a gas pipeline, 500 mm in diametereach, 600 and 1200 mm in some parts,100 bar operation pressure and a totallength of 807 km. More than 1100 watercourses of all kinds, 63 of themparticularly sensitive, had to be crossed.Pipeline bridges were not built, instead,there were 8 HDD crossings with coversof up to 10 metres, the others weremainly achieved using the open cutmethod.

No part of the line was installed abovethe ground, as Permafrost is not aproblem there, and the Russianunderstanding of security and natureprotection is contrary to open lines:Technical failure, or even sabotage, canlead to great damage and permanentinterference, if oil emerges from the line.The TSUREN (Russian FederalRegulators) have also experienced, thatinstallations above the ground aresubject to massive technicalmaintenance and servicing, theirconstruction has proved an immense

strain on the environment – the exampleof the Kamchatka Pipeline has alreadyshown this.

Therefore HDD was applied for the rivercrossings, crossings in open trencheswere only allowed in the winter months,when the soil was deeply frozen.

Tacking stock we can say that the HDDtechnique, as it is today, is effective andeconomical in its application, even inextreme conditions.

3 Techniques Installation3.1 Open trench constructionNaturally, the open trench construction

takes the lion’s share of the total length.Figure 6 shows the typical situation.Before the beginning of work, the futurepath is determined and staked out. Afterthis, the working area is cleared, whichmeans, the removal of any trees andbushes standing within this area whichincludes the ‘right of way’ area (ROW).

In the case of the BTC, the workingspace is 32 meters because the SCP willfollow at a later date, but in the samecorridor a further expansion of merely 12m of the ‚right of way’ zone is necessary.Here, the principle of using the alreadyexisting corridor to protect humans andnature alike, is also applied.

The next step is to excavate a trench,approx. 2.5 m deep, in which the alreadywelded pipe string is lowered later on.Approx. 15 km of open trench are alwaysprepared at this stage. The trench shouldbe backfilled with the same material,especially the cover layer should be thesame as before. Then the surface islandscaped and restored.

In the way the building activities andregional transactions of this BTC pipelineproject should be organised, the buildingsite claims no more than a length of 60km during the complete time. Thebuilding activities should last for 6 to 8weeks in each region. During this time, allpossible efforts to minimise noise, dustand job site traffic should be taken.

3.1.1 Open Crossings

The crossings of roads, rivers, brooksand railway tracks is often performedusing the open trench method. Usuallyunpaved gravel roads are concerned,which are closed and crossed with theopen trench.

Minor roads and railway tracks arecrossed by working one half of the waywhile maintaining the other half for thetraffic.

Dry open-cut crossings of small rivers orirrigation canals is carried by means of aby-pass of the water course into pipes;otherwise, the flowing water is simplycrossed with an open trench. Decisivefactors are the amount of water, functionof the water course, effects of themeasure on the crossing anddownstream area as well as theexpenditure required for restoring theriverside and slope area.

Therefore, every crossing demandsthorough investigations to find out howto avoid too much disturbance forresidents and the environment, how tocarry out the measures as quickly aspossible and how to restore thedisturbed surfaces to their original statein the best possible way.

This kind of application naturally has astrong effect on all persons concernedand the surroundings of the civil works.Even under normal conditions elaboratejob site logistics for the parallel-runningprocesses of excavation, installation,back-filling and restoring works as wellas the required cross and longitudinaltransports in the area of the job site areindispensable. Heat, dust and, most ofall, precipitation aggravate the access tothe job site and turn work in deep terraininto a strain for man and equipmentAppointed time schedules set everyoneunder pressure, making additionalmeasures inevitable in order to ensurethe completion of the job in time. Here,trenchless technologies - assumed thejob site is accessible – are considerablyless sensitive; additional equipment ofthe machine technique allows work evenunder extreme conditions, i.e. largercooling aggregates for great heat orheated shelters built above the unit forcold temperatures.

Therefore, the application of trenchlesstechniques can prevent many negativeeffects of the open-cut construction,reduce the costs for restoring the originalcondition and save additionalmobilisation of resources for completingthe project.

3.2 Plough Technique

In comparison to the open trenchmethod, the pipe and cable ploughmethod is distinguished by reduced


Fig. 6:Open trenching -cross sectionalscheme


disturbance of the surface, very highdaily performance and economicefficiency. Particularly in rural regions,where often the distances are long, freeof obstacles and the geology isconsistent, this method is unbeatable.When applied under water, the plough ispulled across the sea bed by ship,opening a trench in which the pipe is laidand then backfilled again.

The conventional pipe and cable ploughcreates a V-shaped trench for installingthe pipe, back-fill is performed in thenext working step. Ploughs – made inUSA - with a pulling force of 330 tons,depths up to 6.5 ft can be achieved inone single working step. The dimensionsof this kind of plough: length 75 ft x width40 ft; pipes up to 45 inches in diametercan be installed.

Similar dimensions - approximately 70feet wide, 70 feet long and 30 feet high –are the specifications of a marinepipeline plough, which was used for theinstallation of a 24 inch pipeline with atotal length of 35 miles in the EastchesterExtension Project.

These plough methods require ratherlarge working space to the sides, whichrequire a lot of finishing work. Thecompany Georg Föckersperger GmbH,Aurachtal, has developed a basically newinstallation and pipe laying technique inGermany 30 years ago and is improvingthe method since then (Figure 7). Up tonow more than 50,000 km of pipeline,including steel pipe s up to 350 mm ODand casting lines up to ND 250, havebeen installed.

A dissertation from the year 2003determined the loads occurring duringinstallation and converted them into amathematical formula. Accordingly,pipelines can be laid in a way thateliminates damage to the pipe and near-by lines, allowing great single lengths tobe pulled in.

3.2.1 Special Plough – soil conditions

The soil-mechanical processes affectingcohesive and non-cohesive soils during

installation have been examined was partof the dissertation mentioned above.Result of this examination: the ideal soilfor applying the plough technique is wellcompactable and sufficiently stable.

Only slight lifting of the soil on the terrainsurface occurs , the required total pullingforce is low and stress during installationis not severe. Route sections containingboulders, fractured rocks or stones areunsuitable for this method. Soils of thiskind can neither be displaced norcompacted. Depending on the bedding,unfavourable loads may occur,influencing the functioning order or theservice life of the pipe in a bad way.

The investigation also proved, that theload on the cables and pipes isminimised in comparison to conventionalbuilding methods, because the soil isonly slightly disturbed. The applicationrange comprises non-cohesive andcohesive soils. Depending on theconsistency or ground compactness, theability to be displaced has an effect onthe pulling force during installation. Thefriction-reducing effects (which alsoreduce the power requirements) of aBentonite lubrication can also befavourable for the installation procedure.

Cohesive soils with a soft consistencytake longer to settle on the pipe being

installed than non-cohesive soils withtheir loose bedding, cast iron pipes withprotruding collar connections aretherefore hardly suitable for loose, sandysoils.

3.2.2 Special Plough – mode ofoperation

Supported by the cable-pulled specialplough, the pipeline is laid directly intothe void created by the displacementprocess, which is the advantage of thismethod. Here, we must differ betweenthe static or dynamic plough methodwith installation box – the line is leadoverhead to the plough share – and theplough towing method. Plough towingmeans that the line is inserted in thestarting pit and – as the word alreadysuggests – is towed underground into thealready created plough track.

Simply one little starting pit for settingand aligning the plough is required. Theplough blade can be precisely adjustedin its height by hydraulics, allowingprogressive adaptation of the ploughingdepth to the current needs down to 2.0m. The towing winch with its pulling forceof up to 140 t and a cable length of 130m is mounted to an off-road vehicle andbraces itself automatically when reachingthe target.


Fig. 7: Rocket plow – Scheme (Source: Föckersperger GmbH)

Fig. 8: Rocket plowapplication in themud flats (Source:FöckerspergerGmbH)


Plough and plough blade are mounted toa rig with special tyres which can beadjusted in height and track width bymeans of hydraulics, therefore,application is no problem even ininaccessible terrains or when crossingshallow offshore waters. In 2003, themost spectacular application took placeacross the north German mud-flats,when a 5 km long water line to the smallisland Nordstrandischmoor wasploughed in (Figure 8).

Lines with small diameters are alsoinstalled, even in bundles, with trackwarning tape and a daily performance ofup to 2000 – 3000 metres. The so-calledrocket plough is available for largerpipelines, steel lines up to OD 350 andcast iron pipelines up to ND 250 havebeen ploughed in until this day. In 2003, aspecial ATV-DVWK-M139 leaflet waspublished, which documents allapplication ranges, requirements andquality assurance.

The plough method is particularlysuitable for rural areas with a lowpopulation density, great pipeline lengthswith only a few connectionsunderground. Up to now, this methodhas only been used for pressure lines.Crossing small shallow waters andinstalling pipes in slopes is no technicalproblem due to the plough constructionwith universally adjustable wheelextensions.

The utilisation of the plough method hasproved its economic and eco-friendlyvalue for pipe installation below groundwater level. Unpaved terrain is a pre-condition and there should be no largerobstacles in the track. Before theinstallation can commence, the exactposition of crossing lines and theunderground conditions in the line pathmust be determined.

The method is remarkably efficient, time-saving and eco-friendly, because theexcavation of trenches is not necessary,the track of the plough is simplysmoothed down. A very economical,ecological, proven and versatiletechnique with only minimal undergroundimpact is offered to the customer anduser.

3.3 Trenchless Installation

There is a great number of techniquesand methods for underground andtrenchless installation. They all belong tothe category of ramming, fluid assisteddrilling and microtunnelling methods.Mainly roads and railway tracks arecrossed with ramming and drillingtechniques; the other method, HDD, isalso used for undercrossing larger riversand their foreland.

The trenchless method is the obviousalternative, not only when obstacles

occur along the pipeline course, but alsowhen sensitive natural habitats needcrossing and damage has to be avoided.The choice of the right method depends

mainly on pipe diameter, length of thebore, geology and geo-technicalconditions. The dimensions, depth,excavating and set-up of the start andtarget pits, the size (dimensions) of therequired working space as well as themeasures for ground water drainagediffer from one method to the other.

The composition and structure of theground in the geo-technical sense is thedecisive factor for the completion of anydrilling job, a fact, which has to beacknowledged by carrying out asufficient survey beforehand.

3.3.1 Auger Boring

his bore technique uses a protectionpipe which is pressed forward, while anauger removes the spoil at the sametime. This method can be used foralmost any soil type. However, it isnecessary to observe the stability of thesoil structure. Non-cohesive soils andlarger stones cause problems; the firsthave a tendency to flowthe second mustbe easily smashed to pieces to keep thepassages of the auger unblocked.

If the soil conditions are unstable, theauger flight must be pulled back behindthe cutting shoe in order to avoidbreakage of the position front. Otherwisethe auger can work directly in the cuttingshoe area or even be equipped with a

cutting head itself, to excavate the pathfor the protection pipe.

In reference to the size of drillableobstacles, the pipe diameter itself shouldbe either small enough to bore throughwithout upsetting the position, or largeenough to recover these obstacles. Theprotection pipes have lengths of 6 – 12metres and are welded togethersuccessively. You have to make sure ofthe roundness and a smooth surface ofthe pipe in order to keep the frictiondown.

An overcut or the application of pipelubrication can reduce the pipe frictioncaused by forward thrust. In extremecases, the friction forces and the jackingforces may lead to deformation of thepipe and stop the forward thrust.

In the starting pit, the thrust pipe isaligned exactly to the target and runsrelatively stable in its direction, if no outerforces affect the steel pipe. Anyoccurring intercalations or hard layerslying diagonally to the thrust directioncan divert the installation from thedesired direction. The installation takesthe course of the weakest resistance.Especially sliding upward makes it hardto keep the direction.

A larger bore diameter may be helpfulbecause it maintains the exact positionof the medium pipe which is going to beinstalled, the remaining annulus is filled incorrespondingly. If the thrust pipe getsstuck, however, over-boring in counter-heading may help to complete the bore.


Table 1: Soil type classification


If nothing else helps, the thrust must begiven up and filled back.

A certain control of the bore path ispossible when using a slanted drill pipe,which can be twisted by a hydraulicfacility (hydraulic wrench) in the startingpit to turn the pipe into the desireddirection. One-sided pressure applica-tion to the flexible thrust pipe is alsopossible (rudimentary articulation of thecasing near the head activated by rods)with suitable steering presses. Becauserefractions are to be expected, a supportwith laser only makes sense if the augerflight has its own protection pipe.

The use of water for discharging the soilshould be carried out by an experiencedcrew, or not at all. The risk of collapsingis very high, the stability of the roads orrailway tracks which are being crossed,can no longer be guaranteed. Largeamounts of water may flow out if acollapse like this happens beneath theriver bed.

The pits are rather large because theyhave to accommodate the pipe lengthand the forward thrust facility; the finishmay be elaborate, depending on thedepth, perhaps it will need water-proofshoring or drainage. It also means a lot ofwork to remove the bore cuttings fromthe often rather deep pits.

Typical application ranges are diametersfrom 8 – 50 inches, larger diametersshould be installed using the micro-tunnelling method because of thepositional accuracy, smaller diametersare handled best with the displacementmethod. Bore lengths are approximately250 ft; precision lies with +/- 1 percent ofthe driven length.

3.3.2 Ramming Method

The ramming method is an efficient,quickly accessible and feasible methodfor crossing streets, railway tracks andrivers. The pneumatically driven piperamming machines install open steelpipes as jacket or product pipes withdiameters up to 4000 mm and lengths upto 80 m without pressing abutments, insoil formations up to class 5 (partiallyeven through clastic rock), see Figure 9and Figure 10.

The rammer, driven by compressed air,has a cylindrical shape with a cone forconnecting add-on cones, cottersegments and/or soil removal cones oradapters which establish the tight-fittingconnection between the machine andthe pipe. Due to the two gaps in the soilremoval cones or adapters, part of thetension of the spoil which is carriedalong, is released. The application ofcotter segments prevents flaring up ofthe pipes and enables butt-welding ofthe single pipe lengths. The welding

beads of spiral welded pipes have to besmoothed level with the pipe material inthe area of the segment fitting depth inorder to prevent point pressure.

The casing friction of the inner or outerpipe is reduced by cutting shoes creatinga free-cut. Bentonite simplifies pipeinstallation by lubricating the pipe. Dueto its very small displacement volume inthe area around the cutting shoe, heaveof the ground or street surface can beruled out even for thin covers. Thismeans, work can commence even fromshallow pit depths.

Using a pneumatic lifting cushion, therammer is precisely positioned axiallybehind the pipe and tightly fastened withstraps. It is driven by a normal job sitecompressor. Due to the robust one-piececonstruction, an impact energy of 40000kN can be achieved with the largestTracto-Technik rammer at full capacity,which is passed on to the whole pipestring in an optimal way. The installationhas an average speed of 15 m/h. Afterthe ramming work is concluded, the pipeis emptied completely, using waterpressure in combination withcompressed air or water pressure alone -up to DN 500, this procedure is allowedwith compressed air only, after theappropriate security measures have

been taken care of. Larger pipediameters call for manual soil removalwith other auxiliary devices.

Typical for the ramming technique, nextto all the general advantages oftrenchless construction:

• simple, easy-to-transport equipment

• minimal job site set-up

• short equipping and propulsion times

• installation without elaborateabutments

• soil removal after the installation iscompleted

• relative aiming precision

Results of the advantages listed aboveand their consequent practicalimplementation: Due to the technicalpoint of view, the Deutsche Bahn AG(German Railway Company) prefers thismethod to other crossing methods. Andthe Ruhrgas AG, a large German gassupplier, rates the method asrecommendable.

3.3.3 Variations in RammingTechnology

The Ruhrgas AG has investigated thedirect installation of product pipes onseveral job sites. The impact energy andits effects as well as the occurring stress


Fig. 9: Steel pipe ramming – Scheme (Source: Tracto-Technik GmbH)

Fig. 10:Ramming largediameter teel pipes (max. ND 4000) (Source: Tracto-Technik GmbH)


of the thrust pipes was measured. Theevaluation proved that it is unnecessaryto add any additional design loads orprecaution correction values to thecalculation of the thrust pipes, the pipesare not damaged by this method. Wecome to the following conclusion: underconsideration of certain constructionalmeasures, this method is recom-mendable for pipe installation on a largescale. In order to go easy on the gaspipes, a reusable impact pipe should beplaced between the product pipe and thehorizontal rammer. Furthermore, careshould be taken, not to impair lines orbuildings in the neighbourhood byoccuring vibrations.

Another variation of the rammingtechnique is the so-called slick boring.This technique utilises a horizontalrammer to drive home a protection pipe.After removing the soil, the medium pipeis connected. With a winch, an excavatoror some other pulling facility, the borepipe is pulled and then the product pipetakes its place (Figure 11).

Decisive assets are the advantages ofthe ramming method mentioned above,in connection with the reusability of therammed pipes and the economical,direct, exact and gentle installation ofcoated pipeline pipes.

The pipe roofing method is anothervariety for crossing embankments. In thiscase, a protective roof and the contourfor the intended multi-pipe tunnel iscreated by pipe-to-pipe ramming. Afterthe excavated soil is removed and thesite-mixed concrete vault is prepared, apassage for laying several lines has beencreated.

3.3.4 Microtunnelling

Microtunnelling is a trenchless methodwhich is carried out as an unmannedpipe installation with fully automaticcontrol. The jacking pipes are also theproduct pipes; depending on their

function, they are mainly made of steelconcrete, stone ware, glass-fibrereinforced concrete, cast iron or steel.

Microtunnelling is the further deve-lopment of conventional pipe driving to aremotely controlled one. Originally it wasdeveloped for the unmanned, on-targetdriving for short distances of little morethan 100 metres, but meanwhile it resultsin the already mentioned diameters anddistances of several hundred metres.Typical driving lengths – withoutintermediate jacking stations – arebetween 100 and 250 metres. Themaximal driving lengths to be achieveddepend on the pipe type, bearable strainfrom the jacking propulsion forces, soilconditions, measures of possible frictionreduction and the thrust capacity of themain jacks.

At the beginning, the term micro-tunnelling was used as the description ofnon-accessible pipe driving up to DN800 / DN 900 in Germany; meanwhile,thanks to the further development of thistechnology, lines up to 4 metres indiameter can be driven with remotecontrol. The largest possible pipediameter to be transported along ourstreets is the upper limit of the diameter.

This development was made possible bythe application of highly sensitivemeasuring instruments, the installation ofreliable control devices and theadaptation of technologies used forexcavating huge tunnel constructionswith slurry and earth pressure balancedshields. It includes, among others, theexact detection of pressures, volumes,inclinations in the installation area and aprecise control via computer-aidedregulation and control facilities.

Microtunnelling was developed for thelinear and exactly steerable course of thepipe path in height and position, theseproperties are specially required withinthe area of gravity lines, where often onlya smooth inclination of the open channel

are required and the sewer pipe is theinstallation pipe at the same time. Withinthe range of large diameters, curveddrives are possible.

With the suitable choice of cutting tools awide soil spectrum can be excavated;there are suitable working techniquesfrom sand and gravel to rock. Decisivefactor is the service life of the tools,which must be long enough to reach thetarget shaft or at least the nextintermediate shaft. Long distance drivescan be carried out by using intermediatejacking stations.

Furthermore, there is little settlementwith this method. If handled properly, thepressure at the cutting face can be buildup against standing soil and waterpressure, the driven void is immediatelysecured by the thrust pipe. Bentonite isalso used as a drilling fluid for thistechnique. Its task is to support thecutting face, lubricate the annulusbetween pipe and soil and transport thesuspension charged with the cuttings.

Thus characteristic project parametersare the pipe diameter, driving length,topography, depth of the start and targetshafts and the soil condition. With thismethod, even geologically difficult terraincan be bored over long distances.

The job site set-up consists of the pipejacking equipment assembled in thestarting shaft, a container with power unitand control container, settlement tank,recycling unit for the soil-slurry-suspension and a pipe storage. The set-up can be flexibly adapted to theavailable space on sites. The standardshaft is 3.20 m in diameter and can beused for driving pipes up to ND 800 with2 m length; recovery of the unit makes atarget shaft of 2.0 m in diameternecessary. If the jacking frame is turnedaround, it can also be used as a two-sided driving shaft. Larger pipediameters require individual launchshafts, they are built for pipe lengths upto 3.5 m.


Fig. 11: Slickbore application: 1. Bore pipe ramming Slickbore application: 2. Pipe pulling (Source: Tracto-Technik GmbH)


The installation of the jacking pipes ismonitored by a laser beam from theprepared starting shaft. The operator inthe control container traces theinstallation on the monitor. Steeringmotions are carried out by the controlcylinders in the flexible bore head. Acutting wheel excavates the soil,supported by a slurry-water suspension.The suspension flows into the annulusbetween pipe and soil, reducing pipefriction; the outer walls of the followingpipes are also frequently lubricated withBentonite suspension by an automaticlubrication system to keep the frictionlow.

The suspension, mixed with the cuttingsis pumped up by means of its own fluidcirculation (supply and conveyor pipe) toa separation unit and, thus refreshed,returned to the conveying circulation,spoilt suspension is disposed.

Installation in ground water is possiblewithout lowering, because the jackingthrust pipe leaves the shaft through awaterproof seal and enters the preparedtarget shaft in the same manner. Theshafts themselves are established usinga lowering technique with underwaterexcavation, a waterproof ground plate isalso mounted (Figure 12).

The application of the microtunnel boringmachines (MTBM) can be adapted to thegeo-technical conditions; constructed asan earth pressure balanced or slurrymachine it combines a large number ofgreatly differing bore heads. Almost anysoil formation – finest loam, sand, gravelto rock - can be excavated

Of course, exact knowledge of thegeology and the groundwater conditionsis necessary to carry out the installationsuccessfully and without interruption.Important parameters are stability,particle size, water contents, plasticity,ground compactness, consistency andpermeability.

In pipeline construction, the microtun-nelling method is suitable for crossingdifficult terrain. Protection pipes areinstalled for the inserted product pipe.Establishing a so-called multipipeprotection pipe for installing severalsingle pipes could also be an option.

The longest installation of this kind everheard of was the shore approach of theStatoil gas pipelines through the mud-flats near Dornumer Siel. Reinforcedconcrete pipes were jacked beneath adyke and into the tie-in chamber in theNorth Sea. This was a long distanceheading with more than 2.8 km; theconcrete pipe, which accommodatestwo 1000 mm gas lines, has an OD of 3.8meters.

The advantages of microtunnelling canbe seen within the area of protection pipe

installation in urban regions with high-quality surfaces, in crossing difficultterrain with big covers, beneath highground water levels and everywhere else,where restricted spaces does not admitlarge installation areas.

3.3.5 Horizontal Directional Drilling(HDD)

When talking about HDD technology, thefirst thought concerns the drilling of largediameters covering gigantic distances.However, the HDD technique is alsosuitable for short distances and pipeswith just a few centimetres in diameter.Almost all pipe materials, particularlyplastic pipes, but also steel, cast iron andasbestos cement pipes can be pulled in.

Besides pipelines for the transportationand distribution of fluid and gaseousmedia, meanwhile also irrigation anddrainage lines, slope fortifications,contaminant detection, undergroundsanitation and the connection of off-shore plants are accomplished by meansof HDD.

But first of all, it is a method to installpipes underground – bypassing any kindof underground obstacles. Directionaldrilling is a construction method havingless negative impact on environment andnature than any open-cut method.. It isapplied in cases, where any other knowninstallation technique would be eitherimpossible or only possible with a fairlygreat expenditure.

Like any other trenchless method, thediameter and length of the pipeline aswell as the geology with its geo-technicaleffects play an important role. The drillingfluid has an important function – it isresponsible for the support of theexcavation, support and transportationof the soil, but also for reducing jacketfriction when the pipe is pulled in. Just asimportant , of course, is the location andcontrol of the drilling unit in order toperform the installation of the line in theintended path.

Corresponding to the complete range ofdiameters, lengths, materials andfunctions of the planned pipelines,drilling units of different sizes andcapacities are available, and naturallyalso recommendations, rules anddirections of the manufacturers, users,production engineers and contractors.

All kinds of different organisations – forexample the national associations fortrenchless techniques like the germanGSTT and the ISTT as its internationalumbrella organisation, or DCA-Europe(Drilling Contractors Association) and itsAmerican sister organisation DCCA – aredevoted to the task of drawing upguidelines and sharing experienceamongst all persons concerned with thehorizontal drilling technique.

3.3.5.1 The MethodThe HDD method installs hollow rodsunderground, using percussive rotationaland pressure forces. The slanted borehead or a drill bit with a bent sub ismounted to the tip. Via the hollow rodswhich are bored in a shooting manner, aBentonite suspension under pressure iscarried to the tip of the drill; if rock boringheads are applied, this suspension isalso used for driving the mud motors.

The so-called walk-over system is usedas location system for the pilot bore; thisis a transmitter (drill tip) – receivercombination (surface), working by meansof electro-magnetism to locate theposition of the bore head (Figure 13).Deviations are detected and corrected bya steering motion. The application rangeis only a few metres. For complex boreswith existing disturbing influences, aseparate magnetic field is build up.Larger units use the MWD principle(measurement while drilling); originally, itcomes from the deep bore technique andtransmits the data determined by thesensors lying directly behind the borehead back by cable.

The drilling fluid is a composition ofwater and Bentonite (a natural mineral)


Fig. 12: Microtunneling: schematic drawing


and special additives, if required. Itsupports loosening and movement of thesoil near the working face, reducesfriction of the rods and the pipe when it ispulled in and transports the cuttingsaway through the bore hole. Thesuspension loaded with spoil is recycledand freshened up above the ground andreturned to the fluid circulation oncemore.

The drilling fluid should fulfill its task evenin permeable undergound; additivesimprove the composition.

Normally drilling in ground water causesno problems. Still, the pressure and flowconditions should be watched closely inorder to avoid uncontrolled diffusion.Components, like minerals (salts) and thenature of groundwater (pH-value) mightaffect the stability and function of thedrilling fluid.

As soon as the pilot bore has beenestablished, the bore canal is upsized tothe required diameter in one or moreworking steps with additional drillingfluid. Upsizing tools chosen to match thesoil conditions are used; barrel reamersfor soft formations, fly cutters formedium-hard soils and hole openers for

hard rocky conditions. Forward reaming,for which the reaming tool is twistedforward from the side of the rig, using thepilot bore for guidance, is also popular.

The product pipe is pulled in with the lastreaming action. Depending on diameterand soil type, it is sometimes better toperform a stabilising reaming processwith the same diameter before pulling inthe pipe. A swivel is linked between thepipe string and the rotating rods whichallows transmission of the pulling forcesalone .

On the rig side, the site set-up consists

of the HDD rig itself, the power units,storing arrangements, a unit for mixingand recycling the drilling fluid as well asthe control stand (Figure 14). On the pipeside, the pipe string is laid out,connected and brought to the installationplace on suitable facilities (roller blocks,slide surfaces).

Drilling and pulling-in operations arecontinually carried out withoutinterruption, if possible. When the bore iscomplete, its course is measured andrecorded; then it is time for the requiredfinishing works. The site is cleared,abutments of the HDD rig are removed,collecting pits are emptied, refilled andsmoothed down, remains of the drillingfluid are disposed and the area isrestored to its original or previouslystipulated condition.

3.3.5.2 HDD – Machine Technique

The DCA provides 4 classes for HDD rigs(Table 2):

In each category, the bore rigs havedifferent substructures, i. e. an under-carriage (rubber tracks, wheels) with owndrive, a trailer or a steel frame mountedon supports; this is crucially decisive forthe mobility on site, lifting capacity, sizeof the transportation unit and assemblyand disassembly times.

The Grundodrill – Bore Rig 20 Smanufactured by Tracto-Technik, forexample, belongs to the midi class. Witha pushing and pulling force ofapproximately 20 t, pipe diameters up to600 mm and lengths up to 500 m can bepulled in. The built-in percussive hammerhas a capacity of 280 kN of additionalramming force; allowing installation ofthe rods even in rocky soils. With thispercussive unit, the application area ofthe rig is considerably larger thanwithout. Special equipment for solid rockboring with a functional rock drillingengine is also available (Figure 15).

Recently a contract for a 450 t HDDmega-class unit has been awarded toPrime Drilling; it is intended for projectsup to 2 km in length with pipe diametersup to 52“.


Fig. 13: HDD scheme: pilot bore, reaming bores, pipe pulling (Source: Tracto-Technik GmbH)

Fig. 14: Rig side work space

Table 2: HDD rig classification


3.3.5.3 HDD Projects - BasicsIn order to guarantee the feasibility andsuccess of a project, the client has toprovide basics concerning the place ofinstallation. One important point is thetopography with site layout, view fromthe top, terrain profile and the depths ofgroundwater levels. These parametersgive a first impression of the possiblebore path, the distance to certain fixedspots and the best way to arrange thejob site. The term geology includeshistoric surveys as well as viewing andevaluation of available documents whichallow conclusions concerning existingbuildings underground. Prospectivedrilling and sounding out give a goodinsight of the layers and composition ofthe soil; geo-physical investigationscomplement these results concerningthe boundaries of layers.

The following laboratory tests and theinterpretation of the results and findings,under consideration of the applicabledrilling technique, should lead to areliable statement in the groundexpertise concerning the feasibility of theproject in the building ground expertise.

Further statements concerning externallines, buildings underground andclimatologic and hydrographicalconditions and their characteristicswithin the site should also be available.

3.3.5.4 HDD Projects – ProjectConception

The basics of project conception [DCA],or the determination of the bore profileresult from

• entry and exit angles

• first and last bore section

• bending radii

• depth of coverage

• overcut factor

Detailed information concerning thepoints above can be found in the

technical standards of the DCA or theDCCA; however, a few of the standardvalues are listed below:

The entry and exit angles should bebetween 6 and 15 degrees; smallerangles for larger pipe diameters, largerangles for smaller bending radii of thepipe.

The first and last bore sections should bestraight and phase out without bendingradius; 10 – 20 m for large bores and 5 mfor smaller bores.

The type of load, drill rods or pipeline,has to be considered for the minimumbending radius; the bending radius of theupper bend must also be taken intoaccount when pulling in.

Regard the different definitions for thedepth of coverage. The 10 - 15 fold pipediameter is recommended for offshorewaters; due to the risk of blow-outs,values < 5 metres are critical. Country-relevant criteria concerning streets,landing runways and railway tracks mustbe maintained.

A factor of 1.2 (low-friction, stableunderground) to 1.5 (unstable soil withcaving-in tendency) is the approximatevalue for the relation pipe to borediameter [DCA].

According to the DCA, the calculation ofthe required pulling force can beconducted according to the NetherlandsStandard NEN 3651 or the AmericanAGA method. The greatest pulling forcemakes an appearance at the end of thepulling process, when the whole pipestring is almost completely underground.

When dimensioning the bore rig itselfaccording to the pulling force, otheroperation conditions must also beconsidered; for example, starting outafter longer standstill times during thepulling process, or when the bore holehas collapsed the required pulling forcemust be higher. The position of the

pipeline in the bore hole can alsocompulsory powers, depending on lift ordrift. Depending on the diameter and thegeological underground, the factor 2 – 3is recommended as the securitycorrection value.

3.3.5.5 HDD Projects – Aspects ofexecution

Permissions concerning building rights,environmental rights and crossingsshould be known and available at anearly stage. The content of thispermission must correspond exactly withthe chosen method, the appliedtechnique and the time schedule.

The contractor must procure thepermissions concerning traffic rights(transportation, import and exportregulations etc.), working rights (workingtimes, holidays, exceptional permitsetc.), environmental rights (water rights,withdrawal, discharge, disposal etc.) aswell as the country-specific rights on hisown accord.

Delivery and removal of the bore rig canbe a great logistic achievement becauseof the distances and often limitedaccessibility to the job sites. This is alsovalid for delivering spare parts to the site;water should be available in the nearestvicinity, energy is generated by thecorresponding diesel aggregates.

The right of way and access should beprovided by the customer at an earlystage; provision of the required area insufficient size and condition is alsoimportant. A surface of 50 x 50 metres onthe rig side is easily occupied, evenwithout the drilling fluid pits; on the pipeside, the length of the stretch withworking stripes for heavy machines onthe side and the working surface atpulling point at the heading have to bemaintained.

When pulling in the pipe, which isnormally made of steel, ductile cast ironor HDPE, the effects of the materialcharacteristics in the varying installationphases must be considered. Special caremust be taken to protect the pipe and toavoid damage to cover, coating or lining.Consideration of the bending degree,maintaining the bending radius, layingout the pipe line during the pullingprocess and providing a stable and clearbore hole are futher important factors

A major aspect is the composition andrecycling of the drilling fluid. The soilconditions determine the amount ofBentonite and possible additives. Thequality of the drilling fluid plays a hugepart in the success of the bore. Thebetter the drilling fluid is adapted to thesoil with regards to bearing capacity, gelstructure, flowing properties, lubrication,filtrate value and swelling capacity the


Fig. 15:HDD midirigGrundodrill 20 S:pilot bore


better the stabilising effect for the pilotbore and the upsized bore hole is, notforgetting the friction reduction when thepipe is pulled in. The water is either takenfrom waters nearby and filtered or it flowsdirectly from a hydrant or water tank.

Drilling fluids must have a high bearingcapacity together with the current, theymust prevent the sinking of the cuttingsalong the bore course. During circulation,sinking can be avoided by a sufficientviscosity; standstill times have a negativeeffect.

Manufacturers claim, that the stability ofthe bore hole can be improved, swellingof the soil avoided and stickiness of thetools prevented with the right additives.But the stability of the produced borecanal remains the most important factorfor low-friction and damage-free pipepulling.

A mixing unit, driven by electrics orhydraulics, can guarantee the supply ofhigh-quality drilling fluids for the drill rig.The interaction of the components drillrig and mixing and recycling unit must becompatible; the permanent supply withfresh suspension is a must for friction-free drilling action. The size of thecollecting basin, separation and buffingcapacity must also be adequate.Bentonite is available in big packs forlarge units.

For bores which require a large amountof suspension, i.e. rock boring, a

recycling unit makes sense or is evennecessary. The maximal drilling fluidvolume consists of

• volume of the bore (diameter x length)

• loss due to the filter cake

• loss due to precipitation

• volume of the mixing system

For a bore of 1,500 m length, 1066 mmsteelpipe and a bore diameter of 1600mm, this adds up to a volume of 4,000m3 and some 100 tons of Bentonite,which continually has to be separatedfrom the cuttings and completed again.

The practical performance can besupported by software tools like the PDsoftware „Drill Guard“, which is appliedfrom the projecting stage on. Based onthe data of fundamental investigationand planning, specific data of the HDD-rig, parameters of the pipeline andhandicaps due to existing constraints,the ideal bore path is determined.

The evaluation of the maximal pullingforces is helpful for choosing the mostsuitable HDD rig. The different operationconditions, caused by the alternatingfilling up of the pipe string while pulling,are also taken into consideration.

Calculation of the hydraulic parametersdetermine the required fluid, amount ofBentonite and additive, flowing speedand soil discharge quantity during thesingle reaming operations.

These data are entered into a calculationprogram. The entry of dead lines andtimes for every single working step, ofcosts for machines and staff give thetime limit and calculative values for thebuilding process.

3.3.5.6 Performance - Shore Crossing

HDD belongs to the favoured installationtechniques for pipelines in shore areas.The bore commences from the land sideand into the sea. Entry and exit points ofthe bore are positioned to keepdisruption of the surroundings as slightas possible.

In our example (Cliffhead DevelopmentProject) the job site is arrangedapproximately 400 metres behind thedunes; HDD drill rig, mixing, storage,pump and recycling unit, workshop andstem storage are accommodated on asurface of 50 x 50 metres (Figure 16).

On the sea side, the pilot bore emergesfrom the sea bed, approximately 600metres away from the shore, in a waterdepth of around 6 m; the backreamerand, after the reaming processes, themedium pipe also, enter the bore holefrom a swimming platform.

Another popular method is to place thehorizontal drill rig on a pontoon or abarge, in order to install the line inshallow water without trench and in greatsingle lengths – diameter-dependent upto 2000 metres.

3.3.6 Combination of Drill andRamming Technique

The co-operation between drill andramming technique has secured thecompletion of a HDD bore several timesbefore. The multiple applications are:

§ driving an auxiliary tunnel

§ supporting the pipe pull

§ pulling the drill rods

When the auxiliary tunnel method isused, the formations which cannot bebored are holed through and the spoil isremoved by an auger. The drill rods arepulled through the protection pipe andthe HDD rig carries out the further bore,protected by the partial pipe work.

A pilot bore running off course can alsobe “captured” from the target side. Theprotection pipe is rammed into the spacecreated by the bore head tip, clearedagain and then used as an auxiliarytunnel for the pilot bore to emerge in thedirection of the target area (Figure 17).

With the support of the rammingtechnology Grundoram, many HDDbores have already been preserved fromfailure of the bore or the pipe pulling. Theramming machine is placed onto the drillrods or medium pipe during pipe pulling,and helps to keep the drill rods or the


Fig. 16:Overview of HDDjobsite (Prime Drilling)


pipe passage continuously in motionwith its impact support.

If the drill rods break while reaming, forinstance, the ramming machine is placedonto the remaining rods and the courseof recovery is supported by impactenergy, while the excavator takes overthe pulling process.

3.4 Alternatives to HDD - Installation

Alternatives to the HDD technique arepipe driving techniques and crossings inopen trenches; these may be performedin flowing water, after the stream hasbeen by-passed (loop solution), or withbarriers on one side and the help of asheet piling box.

Lifting or floating the prepared pipe linesiphon into position requires extensivepreparations and elaborate equipment. Itmay even become necessary to buildbridges for the reception of the pipeline.Usually alternatives, for example thebridge solutions, are less economical oreven cause additional costs for serviceand maintenance.

It is also common knowledge that thesemethods cause disruption to thesurroundings, and often mar their beautypermanently. A further aspect is thepotential safety risk due to the influenceof third parties.

4. Underground Pipe DrivingMethods - Demands4.1 Maintaining the InternationalStandards

The regulations and the legal positionsnaturally are diverse. Political visionssometimes are able to enforce certaingoals. Due to the practice of integratinginternational financial institutions like theworld bank, IFC, EBRD etc. intransactions, certain regulating elements

are considered. EBRD or IFC, forinstance, have their guidelines forcarrying out their own “due diligence“ ofa project. Besides the economicalaspects, the financial backers also lookout for the results and recommendationscoming from the EIS – the EnvironmentalImpact Statements (e. g. FERC) and theEnvironmental and Social ImpactAssessments (ESIA) – see the example ofthe BTC project.

For the conception, construction,operation and maintenance of pipelines,the guidelines of the OPS (Office ofPipeline Safety), an organisation of theU.S. Department of Transportation, arevalid in the United States. TheDepartments for Energy andEnvironment are also involved. Furtherparties involved in the approving processare the FERC (Federal Energy RegulatoryCommission) or the national oil and gasinstitutions (API), or else they publishcorresponding standards, like the ASCE– American Society of Civil Engineers.The DVGW – Deutsche Gesellschaft desGas- und Wasserfaches – is one of theleading institutions of the Europeancountries, which not only draws up thevalid standards, but is also active ineducating and qualifying the drilling andsupervisory staff for pipeline installation.

In many countries of the world, there areguidelines for pipeline installation, whichlean on the regulations of the OPS. InEurope, the large pipeline operatingcompanies have their own installationrules. There is co-ordination within theinternational gas union and the nationalassociations like the DVGW in Germany.

Before concrete measures can be taken,a more or less intensive bureaucraticprocess, including the public, takesplace in almost all cases. All publicinstitutions which might be affected by

the building measures are involved, fromthe highest national level down to anyprivate association; maybe elsewhere theregional policy and compulsory approvalproceedings are not quite as intensive asin Germany. Whether the projectexecuting organization is the governmentor a company with private legal form,may also be crucial.

4.2 Bore Path Concept andPreparation/Building GroundInvestigation

Planning of the intended bore path andcalculation of the axis points cancommence, as soon as ownershipinformation relating to the path has beenobtained and the right of way can bediscussed.

The measurements accompanying theconstruction include staking out the pathpoints, line measurement in the opentrench, listing the welding seams andtheir presentation in cross-sectionsincluding the depth of coverage, they areused to document the new lineinstallation.

Taking stock, considering the giventopography and seeking informationconcerning existing lines in the bore patharea are preparations for drawing upinventory records according to DIN 2425,DIN 18702 and supplementingregulations of the customer.

In distributing line construction, anoverview building ground investigationfor the stretch selected to accommodatethe bore path is drawn up, no matter ifthe open-cut or the trenchless method isused. The investigation includes thesearch for karstic terrain, loam pocketsor voids close to the surface, soils with ahigh settling phenomenon, i.e. peatmoor, mud, coarse clay, sea clay, limnicchalk etc., slippery zones or groundwater deposits in the bore path. Now isalso the time to clarify the depth of theaverage and top ground water level(maximal level of the ground water), theunderground flow conditions and whereto evade spring and fountain watercollecting areas.

A course through mountain tracks mayrequire additional slope securingmeasures, tunnel tracks or descendinggradients may need additional detailedgeo-technical investigations.

When crossing waters, the waterregulations with the demanded minimumof coverage must be clarified, aninvestigation of the flow conditions,shoring and inclination of the banks isalso important. All regulations relevantfor the protection of forest and naturemust be heeded in forest regions, thedepth of the roots of the largest treesalso requires investigation. Possible


Fig. 17:Pipe rammingassisting pipepulling(Source: Tracto-Technik GmbH)


compensation areas within theaccompanying space around the pipeline path for inevitable impairment of thenatural balance must be included in theplans.

Already existing lines in the path area arehandled in a similar way. Previouslyinstalled utility lines require a certaindistance to the new line; co-ordinationwith the operator line owner is necessary.

Access roads to the bore path anddriving possibilities on site have to beconsidered, also the space for pipestorage, mass balance, assembly anddisassembly of the machines; final checkpaths, landscaping and access tocompressing and monitoring stations areincluded in the plan.

4.3 Pre-Conditions for Final Checks

The more detailed determination of thebore path course should also include thepossibility for constant pipeline check.Helicopter landing and constant pipelinechecks should be possible. Also, thepreconditions for installing parallel datalines and control cables, i. e. for theoperation and control of the stations,should be given from the beginning.

4.4 Building-TechnologicalAdvantages and Specifications

As soon as the parameters listed in point4.1 to 4.4 have been clarified, thedecision is made, whether the course isof poor surface quality and can beworked with open trench methods, orwhether their high-quality anddemanding surface is predestined for thehorizontal drilling technique.

Usually this is valid for all watercrossings, traffic way crossings, crossingof biotopes and nature conservationterrains, all tunnels and almost everyprecipice track. The horizontal drillingtechnique is also recommendable for allterrains with a high ground water leveland soils with a high settling behaviour, inorder to avoid unnecessary expenditure.In karstic terrains and regions withexposed rocks and poor vulnerable soils,the horizontal drilling technique is alsothe best choice.

The space requirements of the horizontaldrilling technique are usually smaller thanthose of soil moving machines, but iflarge drill rigs are used, the space fordrilling fluid recycling units, suspensionmaterial storage and sedimentationbasin must also be regarded. The accesstracks (set-ups of the bore) for siphonsand crossings must not be forgotten.Companies with exceptional drillingequipment naturally also offer planningand calculation software for horizontaldrilling projects.

5 Potentials of TrenchlessInstallation5.1 Comparative Reflections onConstruction Methods

When comparing different constructionmethods, the first aspect is always thefinancial one, namely the direct costs.Indirect costs which are generated by theimpact of humans, nature andenvironment are often ignored. Theemission of dust, noise and exhaust gasduring the complete working time is thefirst great disturbance factor.

These costs are not economicallyinteresting for a project, but the effectson the complete commercial life must notbe swept under the carpet; they togglemobility, cause delays, lead to loss insales, reduce productivity or evenendangering the earnings for a living. Allover the world, there are still regions withinhabitants who depend completely onan intact natural environment. Forfarmers in barren regions, themaintenance or unrestricted utilisation oftheir few fertile fields is vital; fishermenrely on their intact fishing grounds.

A further aspect are consequential costsdue to the work itself, which often occurwhen operations are not carried outcorrectly. Who is charged with the costsfor overhauling works on street surfaces,who pays for subsequent treatment dueto settlement of unprofessionalbackfilling, when the guarantee periodshave run out and the enterprises can nolonger be made liable for damage.

The open-cut construction methodcauses consequential costs, becausenormally stable soil formations aredisturbed by the building measures;damaged slopes start moving, erosionslead to earth movings, surfaces withoutvegetation are generated. Consequentialcosts due to the breakage of pipelinesalready in operation are hard to calculate.

Consequential costs are also caused byline operation: the Peace River wascrossed by a HDD bore of 3600 ft (1039m) in length and 36-in in diameter toinstall the Alliance Gas Pipeline - thedifficulty degree was generallyacknowledged; as a back-up option incase of a failure of the HDD bore, anelaborate and extremely expensivesuspension bridge (two pylons, mainspanning width 490 m, width of the twoside spannings 245 m each ) for thereception of the pipeline was planned,paired off with the costs for maintenanceand servicing for many years.

When confronted with the decision for aninstallation using the open-cut ortrenchless method, we must notcompare the costs alone, sometimes it isalso a question of building culture. Is itreally allowed to let residents and the

surrounding nature suffer from dust,noise and other deragations for manyweeks? How much is an adequatecompensation for frustration andannoyance due to the lost quality of life?

Without comparing exact figures or oneworking method directly to the other, weintuitively come to the immediateconclusion, that the trenchlessconstruction method prevents many ofthe previously discussed disadvantagesright from the start, also beforecommissioning the pipelines. Let us notforget the fact, that often there is noalternative to trenchless installation.

5.2 Economical Aspects

The crucial question, which method ismore economical, often has no simpleanswer. There are too many individualbuilding projects, the marginal conditionsare manifold.

Basically, drawing a comparisonbetween the different methods and theircosts for construction only makes sensefor a concrete project. Still the fewextensive examinations and attempts tomake the costs more transparent byevaluating documents and numerals arewell appreciated. Without going intodetails or trying to evaluate the method,the results of such examinations shall besummarized in the following.

One example is the examination carriedout by NRC – the National ResearchCouncil in Canada. This examinationfrom June 2002 is based on 174 projects;they all are projects of different lengthsand diameters, carried out with differentconstruction methods. In reference to theaverage costs per mm in diameter andmetre in length of all projects, therelations of the costs for HDD to pipejacking to micro-tunnelling are 1 : 1.44 :3.2; compared with open trenchmethods, the costs for the projectswhich have been carried out using theHDD technique lie 23% below the costsfor open trench methods. When onlydiameters were compared, thetrenchless projects up to 940 mm werealso always cheaper, but above 960 mm,some open trench projects were moreeconomical.

The Final Report of the King CountyProject also shows the cost advantagesof the HDD – technique clearly, whencompared to microtunnelling. Whensingle projects are compared, we cometo the conclusion, that the HDD methoddominates the installation of pressureand gradient lines, because the precisionof position and height is not so importantfor these lines. But don’t forgt there arealso the consequential charges and long-lasting life cycle costs

Trenchless Technologies have proved



their value in practice; the methods areup to the technical standard and haveshowed their economic advantages. Inorder to apply these techniquessuccessfully, their potentials but alsotheir limits have to be examined carefullyfor every new project.

5.3 A Contribution to the Availability ofEnergy

Beside transportation by ship, pipelinesassure the supply for the consumer.Trenchless techniques play a big part inpipeline construction; often they are thefocus of attention. They allow theinstallation of paths in topographic, geo-technical or technical conditions which

would make open-cut installationimpossible.

The economic aspect must not beforgotten – this installation method canactually save money while constructionand under operation. An determined borepath is often only possible because oftrenchless installation, detours areavoided, time and money consumingdiscussions are prevented, the utilisationof soil and grounds is only interrupted forthe residents in certain spots or not at all– expenditure for compensation isreduced.

Trenchless Technologies help to makepipeline installation more profitable andenable the safe and economic supply for

the consumer. A high-qualityunderground installation hardly disturbsthe building ground stability, thuspreventing breakage and damage to thepipelines and making their operationrelatively safe. Consequential damage ofthe surface or the environment is almostunlikely.

But not only large transportationpipelines are important, furtherdistribution networks are required forurban regions and cities. With growingpopulation, especially in urban regions,trenchless technologies becomeessential for installing lines for gas, waterand other media quickly, economicallyand safely.


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