ENERGY EFFICIENCY OF TUNNEL BORING MACHINES

ENERGY EFFICIENCY OF TUNNEL BORINGMACHINES

Vitaliy Grishenko

February 2014

TRITA-LWR Degree ProjectISSN 1651-064XLWR-EX-2014:03

Vitaliy Grishenko TRITA-LWR Degree Project, LWR-EX-2014:03

c© Vitaliy Grishenko 2014Degree Project at the Master’s LevelMaster Programme: Water System TechnologyDepartment of Land and Water Resources EngineeringRoyal Institute of Technology (KTH)SE-100 44 STOCKHOLM, SwedenReference to this publication should be written as: Grishenko, V. (2014) "Energy Efficiency of TunnelBoring Machines" TRITA-LWR Degree Project, LWR-EX-2014:03

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Energy Efficiency of Tunnel Boring Machines

SUMMARY IN SWEDISH

Herrenknecht AB är en tysk världsledande producent av tunnelborrmaskiner. Företaget tillverkaren rad olika tunnelborrmaskiner lämpade att användas i alla geologiska miljöer och leder även tun-nelprojekt över hela världen. Herrenknecht AB visar upp en stark medvetenhet och omsorg för demiljöfrågor som rör deras produkter, däribland energiframställning och de stödjer forskning kringenergieffektivitet som eftersträvar intelligent design av en "grön" tunnelborrmaskin.Syftet med denna studie är att framställa en "status quo"-rapport rörande energieffektivisering av tretyper av tunnelborrmaskiner utvecklade av Herrenknecht AB (Hardrock TBM, EPB TBM och Mix-shield TBM). Målen med studien är följande:

• Uppskatta kvaliteten på de tillgängliga dataloggarna, nödvändiga för energieffektivitetsstudien;

• Uppskatta energibesparingspotential med fokus på de huvudsakliga energikonsumenterna, tvåhuvudsakliga besparingsalternativ behandlas:

– Energieffektivitet genom design;– Effektiv energianvändning vid drift;

• Identifiera korrelation mellan energikonsumtion och förändringar i geologiska egenskaper för deprojekt där detaljerad geoteknisk information är tillgänglig.

Inom ramen för denna studie analyseras totalt 39 projekt, baserade på lagrade energikonsumtionslog-gar, specifikationer av maskiner och installerad utrustning såväl som geotekniska rapporter samt dådet är applicerbart geologiska profiler från tidigare tunnelbyggen. Rapporten innehåller också res-ultatet av tidigare behandlad data (genomfört av Benedikt Broda, tidigare trainee vid HerrenknechtAB). Metodologin baseras huvudsakligen på användandet av beräknings-, plottnings- och statistiskafunktioner i Microsoft Excel och MATLAB.Denna studie bekräftar att det finns datakvalitetsproblem och poängterar behovet av datakvalitetskon-troll. De övriga resultaten av analysen identifierade specifika skillnader mellan energikonsumtionhos de tre analyserade tunnelborrmaskinerna. Användningsanalysen betonar behovet av optimeringav utformandet av tunnelborrmaskinens energimatningsenheter och huvudkonsumenter. Studien avden geologiska påverkan på energikonsumtionen visade inte något generellt signifikant samband mel-lan energikonsumtionen för samma maskiner när de borrar genom sektioner i liknande geologiskamiljöer. Orsakerna till dessa observationer diskuteras i detalj.Sammanfattningsvis visar resultaten från denna studie att det finns en viss energibesparingspotential,vilken kan nås genom att till exempel bättre anpassa maskinernas utformning till lokala geologiskamiljöer och genom minskning av energikonsumtion då arbetet ligger nere. En strategi för en imple-mentering av energieffektivisering som indikerar fortsatt nödvändig forskning föreslås och diskuteras.

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SUMMARY IN ENGLISH

Herrenknecht AG is a German world-leading manufacturer of Tunnel Boring Machines. The com-pany produces a wide range of Tunnel Boring Machines, suitable for operation in all geological en-vironments and is leading tunnel construction projects worldwide. Herrenknecht AG demonstratesa strong awareness and concern regarding the environmental issues associated among others with en-ergy production and supports research on the Energy Efficiency (EE) of their products, aimed at thedevelopment of intelligent design for a green Tunnel Boring Machine.The aim of this project is to produce a ’status quo’ report on EE of three types of Tunnel BoringMachines developed by Herrenknecht AG (Hardrock, EPB and Mixshield TBM). The goals of theresearch are as follows:

• To assess the quality of the available data logs, necessary for the EE study;

• To assess energy saving potential with focus on the main energy consumers, covering two mainsaving options:

– EE by design;– Effective energy use at operation.

• To find correlations between energy consumption and changes in geological properties for theprojects where detailed geotechnical information is available.

In the framework of this research 39 projects in total are analysed, based on the filed energy consump-tion logs, specifications of the machines and the installed equipment as well as on the geotechnicalreports and when applicable geological profiles from previous tunnel construction projects. The pa-per also includes results of already processed data (conducted by Benedikt Broda, former trainee atHerrenknecht AG). The methodology is mainly based on utilisation of calculation tools, plotting andstatistical functionalities of Excel and Matlab.The findings of this study confirm the existence of data quality issue and highlight the necessity of dataquality control. The further outcomes of the analysis allowed identification of specific distinctionsbetween energy consumption of the three investigated TBM types. Moreover the utilisation analysisstresses the necessity for optimisation of the layout of TBMs energy supply units and main consumers.The study of geological influence on energy consumption generally did not demonstrate significantconformity between the energy consumption of the same machines boring through sections withsimilar geological environments. The reasons for these observations are discussed in detail.To sum up, the results of this survey suggest that there is a certain energy saving potential, which isachievable by e.g. better adjustment of the machines’ layout to the particular local geological envir-onments and through reduction of energy consumption during idle periods. An EE implementationstrategy, indicating further research needs, is suggested and discussed.

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ACKNOWLEDGEMENTS

First of all I would like to thank Andreas Kassel, my supervisor at Herrenknecht AG, for providingme with all the necessary information and advice especially during the familiarisation phase as well asfor his help on the refining of the report. I would also like to thank Prof. Bo Olofsson for his adviceand recommendations throughout the project. I am also indebted to Benedikt Broda, former traineeat Herrenknecht AG, who developed and documented the methodology I used for the substantialpart of the research. Special thanks also go out to Andre Heim, Martine Siefert, Florentine Stiefeland other representatives of Herrenknecht AG, who supported me on various issues along my stayin Schwanau. Moreover I would like to thank Erasmus Mundus TARGET project and its employeesfor enabling my studies at KTH. Last but not least I would like to thank my family, especially mymother, Valentina Grishenko, who’s invaluable support enabled me to be, where I am now, my wife,Ekaterina Golubina, for her love and support and my grandfather, Ivan Kabanov, for being a greatexample in my life.

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ABBREVIATIONS

CAI Cerchar Abrasiveness IndexEC Energy ConservationEDA Exploratory Data AnalysisEE Energy EfficiencyEIA Environmental Impact AssessmentEPB Earth Pressure Balance (Tunnel Boring Machine)GHG Green House GasHK Herrenknechtt AGKTH Kungliga Tekniska Hogskolan (Royal Institute of Technology, Sweden)MDB Main Distribution BoardN/A Not AvailableRMQ Rock Mass Quality (index)SME Small and Medium (medium sized) EnterprisesTBM Tunnel Boring MachineUCS Uniaxial Compressive StrengthUTS Uniaxial Tensile Strength

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SYMBOLS

Symbol Name UnitP active power [kW]τ torque [kNm], [MNm]ω rotational speed [rpm]Q flow rate [m3/hour]P pipeline pressure [bar]EF pump specific efficiency factor [-]Umean mean utilisation [%]Umax maximum utilisation [%]Vring ring volume [m3]Em energy consumption per excavation volume [kWh/m3]Pm active power per excavation volume [kWh/m3]k − value hydraulic conductivity [m/s]Cu not drained cohesion [kN/m3]UCS uniaxial compressive strength [MPa]RMR rock mass rating [-]CAI Cerchar abrasiveness index [-]RQD rock quality designation [%]

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Contents

SUMMARY IN SWEDISH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iiiSUMMARY IN ENGLISH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vACKNOWLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . viiABBREVIATIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ixSYMBOLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2 Aim and limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.3 Scope and methodology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 LITERATURE REVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1 Tunnel Boring Machines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2.1.1 Hardrock TBMs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42.1.2 Closed System TBMs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

2.2 Energy Efficiency of Tunnel Boring Machines . . . . . . . . . . . . . . . . . . . . . . 92.2.1 Boring system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.2.2 Thrust and clamping system . . . . . . . . . . . . . . . . . . . . . . . . . . . 102.2.3 Muck removal system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.2.4 Support system . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112.2.5 Research trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

2.3 Environmental impact and European legal framework . . . . . . . . . . . . . . . . . 132.3.1 Energy Efficiency and Energy Conservation . . . . . . . . . . . . . . . . . . 132.3.2 Legal framework in Europe . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

3 METHODOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.1 Data analysis software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153.2 Data analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

3.2.1 Calculation of the active power . . . . . . . . . . . . . . . . . . . . . . . . . 163.2.2 Power utilisation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.2.3 Energy consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.2.4 Exploratory Data Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173.2.5 Ansari-Bradley test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183.2.6 Kruskal-Wallis test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

4 DATA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.1 Geotechnical information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184.2 Energy consumption data assessment . . . . . . . . . . . . . . . . . . . . . . . . . . 204.3 Additional sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

5 RESULTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.1 EDA Analysis of Hardrock TBM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205.2 EDA Analysis of EPB TBM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225.3 EDA Analysis of Mixshield TBM . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235.4 Comparison of the investigated machine types . . . . . . . . . . . . . . . . . . . . . 25

5.4.1 Summary of utilisation analysis . . . . . . . . . . . . . . . . . . . . . . . . . 25

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5.4.2 Energy consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265.5 Influence of geological conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

6 DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286.1 Energy saving potential . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

6.1.1 Effective energy use at operation . . . . . . . . . . . . . . . . . . . . . . . . . 286.1.2 EE by design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

6.2 Geology dependence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316.3 Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

6.3.1 Safety issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326.3.2 Productivity losses and consumer awareness . . . . . . . . . . . . . . . . . . 326.3.3 On-site operation techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

6.4 EE implementation strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327 CONCLUSIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36OTHER REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

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ABSTRACT

Herrenknecht AG is a German world-leading Tunnel Boring Machines manufacturer showing strongawareness and concern regarding environmental issues. The company supports research on the EnergyEfficiency (EE) of their products, aimed at the development of intelligent design for a green TunnelBoring Machine. The aim of this project is to produce a ’status quo’ report on EE of three typesof Tunnel Boring Machines (Hardrock, EPB and Mixshield TBM). In the framework of this research39 projects are analysed using calculation tools, plotting and statistical functionalities of Excel andMatlab. The findings of this study inter alia confirm the existence of data quality issue and highlightthe necessity of data quality control, allow identification of specific distinctions between energy con-sumption of the three investigated TBM types, and stress the necessity for optimisation of the layoutof TBMs energy supply units and main consumers. Moreover the results of the survey suggest thatthere is a certain energy saving potential, which is achievable by e.g. an adequate selection of themachine type prior to start of a given project and better adjustment of the machines’ layout to theparticular local geological environments. An EE implementation strategy, indicating further researchneeds, is suggested and discussed.

Keywords: Energy Efficiency; Gripper TBM; Single Shield TBM; Double Shield TBM; DoubleShield TBM; Earth Pressure Balance TBM; Mixshield TBM; Herrenknecht AG

1 INTRODUCTION

The acknowledged scarcity of natural resourcesresulted in general trend towards the greenproduction and environmental friendliness ofthe products and services. This trend isstrongly supported by various legal documentson international, regional and national levels.In European Union a number of documentsand policies were developed in order to pro-mote and support green products and services.EUROPE 2020: A strategy for smart, sustain-able and inclusive growth, EE Plan 2011 andEE Directive 2012/27/EU are some of the ex-amples of such papers dedicated to improve theEE throughout the European Union.Herrenknecht AG is one of the world leadingTunnel Boring Machines production compan-ies, located in Germany. The company pro-duces a wide range of Tunnel Boring Machines,suitable for operation in all geological environ-ments and is leading tunnel construction pro-jects worldwide. Herrenknecht AG demon-strates a strong awareness and concern regard-ing the environmental issues and among otherssupports research on the EE of their products,aimed at the development of intelligent designfor a green Tunnel Boring Machine.

1.1 BackgroundAround 5000 years ago the humankind startedto work on construction of tunnels for vari-

ous purposes. The tunnels were, for example,built in order to protect the goods and people,to secure secret underground passes and to en-able mining or improvement of transportationroutes (Maidl et al., 2012).The rapid development of tunnelling techno-logy started during the industrialisation age inthe beginning of the 19th century, when therailway network was extensively built. Drillingand blasting method was mainly used in thehard rock environments and the developmentof tunnelling was strongly influenced by thedevelopment of drilling equipment for drillingholes for the explosives. At the same time therewere attempts to excavate the rock completelyby machine (Maidl et al., 2008).The first mechanised full face TBM was paten-ted in 1876 by John Dickinson Brunton andGeorge Brunton (Maidl et al., 2012). The con-struction scheme of this machine and a shortdescription are demonstrated in the figure 1.’The shield had a hemispherical rotating cut-ting head built up of single plates. The cut ma-terial was intended to fall into mucking buck-ets mounted radially on the cutting head. Thebuckets threw the excavated material onto aconveyor belt, which transported it backwardsout of the shield. The cutting head itselfwas turned by six hydraulic cylinders, whichworked against a ratchet ring fixed to the cut-ting head’ (Maidl et al., 2012).

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Figure 1: First mechanised full face TBM de-veloped by J.D. Brunton and G. Brunton, pat-ented in 1876. Source: Maidl et al. (2012).

In the first half of the 20th century, tunnellingmachines were effectively used for driving gal-leries in potash mines. As a result a number ofmachines were developed, showing a strong de-velopment trend between machine generationswith increased quality and boring capacity (e.g.advance rates) of the modern machines of thattime. The breakthrough to the development ofthe today’s TBMs did not occur until the 1950s,when the first open gripper TBM with disc cut-ters as its only tools was developed (Maidl et al.,2008).With a small delay the tunnel boring ma-chines technology has started its developmentin Europe, with such German manufacturers asDemag and Wirth, which began building TBMsof North American type in the 1960s. Themachines were mostly intended for hard rock.Only the developments of 1970s and 1980s al-lowed for driving tunnels through brittle rockand the enlargement of tunnel sections. At thisstage the consideration of the stand-up time ofthe soil/rock becomes particularly important.This has also led to the necessity in support sys-tems, causing their gradual development fromsteel installations, anchors and mesh-reinforcedshortcrete to segmental lining (Maidl et al.,2008).The various underground constructionsnowadays are widely used. The types ofapplication include placement of undergroundtraffic constructions, connections for energyproduction sites, storage laboratories (e.g.

for highly radioactive materials) and securityrooms, walk-in passages as well as utilisations(e.g. electric supply, communications, watersupply and sewage removal). The necessity inunderground constructions is especially highin densely populated areas, where the space onsurface is limited (Maidl et al., 2012).As a result of the high demand in effective tun-nelling the tunnel boring technology has de-veloped further over the period of the last dec-ades, which is evidenced by both the high levelof development of the conventional boring ma-chines and by the appearance of a wide rangeof new TBMs featured with improved equip-ment allowing for tunnelling in problematicgeological environments. According to Maidlet al. (2008) the shielded TBMs have in mean-while reached a state of perfection in Switzer-land, which is indicated by the high advancerates even in changeable geological conditions.In this research three main types of TBMs willbe investigated:1. Hardrock TBMs (Gripper TBM, SingleShield TBM and Double Shield TBM);2. Earth Pressure Balance Shields TBM;3. Mixshield TBM.The main principles behind the operation ofeach of these TBM types and general designfeatures are described in the literature reviewsection under the respective headings. Eachof these machine types is suitable for a cer-tain range of geological conditions. In generalone can say, that Gripper TBMs are suitablefor good rock with high stand-up time and lowfracturing, Single and Double Shield TBMs aremore suitable for low water content fracturedhard rock, whereas EPB and Mixshield TBMsare designed especially for soft rock, soil andhighly fractured hardrock especially with highwater contents. The difference between thelast two is that Mixshield TBMs are more suit-able for the geological environments containinglarge amounts of groundwater.There are several issues concerning EE ofTBMs, which are caused by different applica-tion practices. For example according to Kassel(2013) the clients tend to choose the equipmentbased on their working experience, giving pri-ority to the machines they used before and gen-erally ignoring the desirable adaption of thesolution to the particular geological environ-

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ments. This may often negatively influence theadvance rates and cause higher total costs of atunnel construction project. Moreover it dra-matically deteriorates the EE of a project. Theenergy costs are however minimal when com-pared with the total costs of the TBM machinesand thus represent rather an insignificant sharein the overall costs of a project (Kassel, 2013).As a result the costumers generally neglect en-ergy costs and do not try to implement energyeffective boring techniques.

1.2 Aim and limitationsThe aim of this project is to produce a ’statusquo’ report on the EE of three types of TunnelBoring Machines developed by HerrenknechtAG (Hardrock TBMs, EPB and MixshieldTBM). The research is based on the filed en-ergy consumption logs, specifications of the ma-chines and the installed equipment as well as onthe geotechnical reports and when applicablegeological profiles from previous tunnel con-struction projects. It should include the res-ults of already processed data (conducted by Be-nedikt Broda, former trainee at HerrenknechtAG) and the new data from 2011-2012 to be pro-cessed within this master thesis.The goals of the research are as follows:

1. To assess the quality of the available datalogs, necessary for the EE study;

2. To assess energy saving potential with fo-cus on the main energy consumers, cover-ing two main saving options:

(a) EE by design (optimisation of theinstalled power of the main con-sumers);

(b) Effective energy use at operation (idlehardware deactivation).

3. To find correlations between energy con-sumption and changes in geological prop-erties for the projects where detailed geo-technical information is available.

The given research has a number of limitations.These include e.g. the absence of data of applic-ation of different machines in the same or evensimilar geological environments (a quality, sig-nificantly affecting advance rates), pre-processed

nature of the studied datasets, low share of en-ergy costs in the overall construction project ex-panses and relatively low energy costs in gen-eral.

1.3 Scope and methodologyIn total 39 previous tunnelling project cases areto be analysed in the framework of this mas-ter degree project, including 15 Hardrock TBMs(Gripper TBM, Single Shield TBM, DoubleShield TBM), 19 Earth Pressure Balance ShieldTBMs, and 5 Mixshield TBMs.The data on energy consumption, descrip-tions of the respective geological environmentsas well as necessary information about thedesign of the machines under investigationare collected from various representatives ofHerrenknecht AG personnel responsible for therespective projects. For the collection and pre-liminary analysis of the data internal softwareand network tools were used. The data is ana-lysed using calculation tools, plotting and stat-istical functionalities of Excel and Matlab.The research project is limited to the analysisof 39 preselected previous tunnel constructioncases and includes the results of further 24 pro-jects, analysed by Benedikt Broda. Duringthe selection the availability and the quality ofthe data is considered giving higher priority tothe projects with available energy consumptiondata and geotechnical information.

2 LITERATURE REVIEW

2.1 Tunnel Boring MachinesThere are a wide variety of Tunnel Boring Ma-chine types (Fig. 2). The diversity of TBMsis determined by the variety of geological andgeotechnical conditions the machines are oper-ating in. Many of the TBM types can be ap-plied in various geological environments, butmost of the introduced developments allow fora better fit to the particular often more diffi-cult conditions. As a result some of the TBMsare more adapted for certain geological envir-onments then the others and there is no univer-sal TBM. For instance, Gripper TBMs are nor-mally used in good hardrock conditions withlittle fractures and low water content. In thisrock type, where the stand-up time of the rockis relatively high, there is no or rather little riskof water inflow or rock falling. Closed system

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Tunneling

Machines

...

Tunnel

Boring

Machines

(TBM)

...

TBMs with

full-face

excavation

Shield

TBMs

Gripper

TBMs

TBMs with

cutting

wheel

shield

TBMs with

roof shield

and side

steering

shoes

TBMs with

roof shield

Open TBMs

Closed

systems

Double

shield

TBMs

Single

shield

TBMs

Earth

Pressure

Balance

support

(EPB)

Fluid

support

application

(Mixshield)

Figure 2: Overview of tunnel driving machines according to Maidl et al. (2008) (modified).

tunnel boring machines (such as Mixshield andEPB) on the other hand are best suitable for op-eration in unstable soil, fractured soft and hardrock containing groundwater.

In case of unforeseen geological conditionschange certain risks occur and special engineer-ing solutions need to be applied. The examplesof such solutions include freezing of groundwa-ter with liquid nitrogen in order to shortly stopgroundwater inflow, installation of additionalshield protection in order to secure safe work-ing environment for the TBM crew in fracturedrock or installation of additional lining supportsystems in order to enable secure tunnel con-struction. Many of such measures need to beimplemented in combination with the others.This might cause substantial cost increase of thetunnel construction project.

The selection of a particular TBM solution isthus always a trade-off between the initial costsof the machine and additional costs, which canoccur during the tunnelling. In order to makean informed decision many aspects should be

taken into account. This is probably one ofthe main reasons for an extensive geophysicalinvestigation of the planned construction site,which has to be conducted prior to the selec-tion of the suitable TBM.The figure 2 is a modified compilation fromDAUB (2010) and DAUB (1997). In this re-search only full face excavation tunnel boringmachines will be taken into account, with aparticular focus on Gripper TBM, Single shieldTBMs, Double shield TBMs, Earth PressureBalance Support TBMs and Mixshield TBMs(denoted with bold text in the figure 2).

2.1.1 Hardrock TBMsThis subdivision of Gripper TBM, Single andDouble shield TBMs into the Hardrock TBMsection is rather subjective. Both closed systemsTBMs considered in this research can also beused in hard rock. This will however requirea certain level of modification especially onthe cutter wheel, which has to sustain higherstresses when applied to hard rock. The facts,descriptions and further thoughts presented in

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Figure 3: Overview of various machine sys-tems of tunnel boring machines with full-faceexcavation. Source: Maidl et al. (2008).

this subsection of the report are mainly basedon the information gained from Maidl et al.(2008).

Gripper TBMGripper TBM is a classic example of a TBM ma-chine. The name originates from the clampingunits aka grippers. There are several variationsof Gripper TBM, including open TBM, roofshield TBM, roof shield and side steering shoesTBM, and cutter head shield TBM (Fig. 3). TheGripper machines are in general applied in hardrock conditions with medium to high stand-uptime and have rather less sophisticated design.Open TBMs have no static protection againstfalling rock behind the cutter head. This typeof TBMs is nowadays used only for construc-tion of tunnels with small diameter. Roof shieldTBM contains partial static protection roofs se-curing the safe working conditions for the crew.It is applied in stable hard rock, where only

minor rock-falls are to be expected. An exampleof a roof shield Gripper TBM during assemblyis demonstrated on the figure 4. The side steer-ing shoes provide additional protection of thefront part of the machine during advance andallow steering of the cutter wheel prior to andduring the boring process. The cutter headshield TBMs provide protection from the fall-ing rock for the area in the direct proximity ofthe cutting wheel.In order to produce the necessary thrust forcebehind the cutter head, clamping units aka grip-pers of the machine are used. These are hy-draulically pressed against the tunnel walls inradial directions. Although clamping forces ex-erted through clamping units, especially grip-pers, may negatively impact the stability ofthe surrounding rock, various sources (DAUB(2010), Maidl et al. (2008), Olofsson (2012))insist that TBMs are generally more environ-mentally friendly due to the low impact of cut-ter head on the surrounding rock, especiallywhen compared to such conventional methodsas drilling and blasting.The application of Gripper TBM is especiallyeconomically effective in the rock environ-ments where no or little rock support isnecessary. In fractured rock with low stabilitythe installation of steal mesh, anchors and othersupport constructions should be conductedas close to the cutting wheel as possible. Thegrouting on the other hand should take placein the gentry area in order to reduce fouling(DAUB, 2010). According to Maidl et al. (2008)the development of rock support installation

Figure 4: Roof shield Gripper TBM ø 3.8 mdeveloped by Herrenknecht AG during the as-sembly in Schwanau (Germany).

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systems has the highest potential for theimprovement of overall increase in advancerates of Gripper TBMs, whereas the furtherreduction of the boring time would only leadto minor improvement.

Single ShieldThe Single shield Tunnel Boring Machines arewidely used in hard rock with short stand-uptime and in fractured rock. The machine isequipped with a shield covering the entire ma-chine area starting from cutter head (Fig. 3).The Single shield machines are equipped with asupport installation system. The support can beeither permanent or temporary and representsa tube made of reinforced concrete. The tube isbuilt from segments, the number of which de-pends on the machine design, the diameter ofthe tunnel face and other project specifications.The lining segments are installed under the pro-tection of the shield.In contrast to Gripper TBM the thrust forcesare exerted onto the existing tunnel supportconstruction. The properties of the last shouldcorrespond the geological environments thetunnel is being advanced through in order toprevent segments from cracking and fracturing.Cutting wheel as well as most other designelements is similar to those of a Gripper TBM.

Double ShieldThe Double Shield tunnel boring machines areapplied in the conditions similar to those ofsingle shields. Double shield machines how-ever have some important constructional differ-ences. First of all, the Double shield TBMs con-sist, as one can anticipate from the name, of twoshields (Fig. 3). The front shield covers the areafrom cutting wheel to the connecting telescopicjacks. The rear shield also called gripper, or themain shield, contains clamping units. The ma-chine can either use tunnel support in order topush off and create necessary thrust and torque(in soft geological environments) or the clamp-ing units of the gripper shield to radially pushto the tunnel walls.As a result of such design in good rock condi-tions the machine can move forward transfer-ring the thrust and torque forces either to sup-port lining or via the rear gripper unit. Thisenables continuous operation and installation

of lining and thus allows increasing advancerates. This design however has its disadvant-ages in some cases, when the rear shield getsblocked due to the fractured rock material en-tering the telescopic jacks. Moreover the ad-vantages of Double shield machines can be lim-ited in certain geological conditions. For ex-ample, in stable rock types the construction oftunnel support can be excluded (DAUB, 2010)and thus only gripper unit can be used. Softrock, on the other hand, only allows operationof tunnel support clamping units and thus grip-per unit remains idle.

2.1.2 Closed System TBMsThe closed system Tunnel Boring Machines aredesigned to sustain difficult geological environ-ments consisting of e.g. soil, unstable or frac-tured soft or hard rock with very short stand-uptime, often containing high amounts of ground-water.Special equipment systems are used in order tooppose groundwater and earth pressure and pre-vent tunnel face from uncontrolled falling orgroundwater from massive inflow. The closedsystem TBMs can be classified further based onthe type of tunnel face support system utilised.In this report only two categories will be takeninto consideration: Earth Pressure Balance Sup-port TBMs (EPB) and Mixshield TBMs (fluidsupport application).The application of closed system TBMs al-lows reducing negative environmental impactof tunnelling due to their ability to operate ingroundwater rich geological conditions, wherethe reduction of groundwater level is either im-possible or forbidden (DAUB, 2010).This subsection of the report is written mainlybased on the information found in the book(Maidl et al., 2012). When otherwise thesources are indicated after the respective bits oftext.

Mixshield Tunnel Boring MachinesThe shielded TBMs with fluid support applica-tion aka Mixshield TBMs use pressurised fluidas medium in order to provide support to thetunnel face. The main elements of a MixshieldTBM are (Fig. 5):

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Figure 5: Schematic design of Mixshield Tun-nel Boring Machines (Source: HerrenknechtAG).

(1) Cutting wheel or cutter head (main excava-tion tool);(2) Excavation chamber (the area of the shield,where the cutting wheel rotates);(3) Pressure bulkhead (separates the section ofthe shield under atmospheric pressure fromworking chamber);(4) Feed line (supplies bentonite suspension);(5) Air bubble (injects the bentonite suspensioninto the excavation chamber);(6) Submerged wall (separates the excavationchamber from the working chamber);(7) Reinforced lining segments (secure the sta-bility of the tunnel);(8) Erectors (install the reinforced lining seg-ments).During the application of a Mixshield TBMboth the existing earth and groundwater pres-sures are compensated (Fig. 6). This type of sup-port systems is mostly utilised in coarse-grainedand mixed-grained soil types. The groundwa-ter level should be located at a considerable dis-tance above the tunnel roof.In order to protect tunnel face working cham-ber is separated from the tunnel by a bulk-head. The required face support pressure canbe very precisely regulated using the installedsubmerged wall, delivery rate of feed pump andremoval rate of the slurry pump. Prior to oper-ation the face support pressure has to be calcu-lated for the entire length of the tunnel (DAUB,2010).The soil is excavated by the cutting wheel andhydraulically removed from the tunnel. The

Figure 6: Main principle of the slurry (fluid)support. Source: Maidl et al. (2012).

stones and boulders, which cannot be pumpedout, are ground by the stone crusher. The sep-aration of the excavated soil from the supportfluid is necessary (DAUB, 2010). It is usuallyconducted outside from the tunnel as it is de-picted on the figure 7.

The density and respective viscosity of thefluid medium should be variable, dependingon permeability of the geological environment.Bentonite suspensions are often applied as con-ditioners for this purpose (DAUB, 2010). Thebasic idea behind the introduction of the sup-port medium is to build an impermeable mem-brane between the suspension and the soil. Thisprocess strongly depends on the permeability ofthe soil. In low permeability soils and with ap-propriate amount of bentonite, the suspensionunder the pressure difference penetrates the soil,building the impermeable membrane (Fig. 8: a).This is a rapid process that takes approximately1 to 2 seconds.

In the highly permeable soil conditions (per-meability over 5x10−3[m/s]) the developmentof a membrane on the tunnel surface ishampered by the uncontrollable flow of benton-ite suspension into the surrounding ground(Fig. 8: b). Adding fine-grained material orother compounds, allowing the improvement ofrheological properties of the fluid, can solve thisproblem.

In stable rock with long stand-up time the fluidsupport system can be run in the open modewithout application of pressure using water asa support medium (DAUB, 2010).

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Figure 7: Hydraulic muck removal during the excavation of the Radau header. Source: Maidl et al.(2008).

Earth Pressure Balance Shields Tunnel BoringMachines

The Earth Pressure Shield TBMs have struc-tural similarities with Mixshield TBMs.However there are some substantial differences.As shown on the figure 9 the main elements ofthe EPB TBMs are:(1) Cutting wheel (main excavation tool);(2) Excavation chamber (the area of the shield,where the cutting wheel rotates);(3) Pressure bulkhead (separates the section ofthe shield under atmospheric pressure fromexcavation chamber);(4) Thrust cylinders (push the machine further,creating pressure and enabling the excavation);

Figure 8: Membrane build-up and penetrationmodels. Source: Maidl et al. (2012).

(5) Screw conveyor (removing the excav-ated muck from the excavation chamber);(6) Erectors (install the reinforced lining seg-ments);(7) Reinforced lining segments (secure thestability of the tunnel).

In EPBs the excavation chamber (2) is separatedfrom the tunnel by the pressure bulkhead (3).The mixing units located on both the backsideof the cutting wheel and on the bulkhead securethe proper consistency of the excavated muck.The pressure sensors located on the front sideof the bulkhead allow the pressure control. Theexcavated material is transported from the ex-

Figure 9: Schematic design of an EPB TunnelBoring Machines. Source: Herrenknecht AG.

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Figure 10: System groups of a Tunnel Boring Machine. Source: Maidl et al. (2008).

cavation chamber by a pressure-tight screw con-veyor (5).The support pressure in the working chamberis controlled by changing the screw conveyorrotation speed or via volume of injected condi-tioning matter (DAUB, 2010). The apt pressurelevel should be created in the excavated muck,so it gets in equilibrium with the forces exertedon the tunnel face.The main principle of tunnel face support israther similar to that realised in the machineswith fluid support system. However there aresubstantial differences in support pressure con-trolling as well as in muck transportation tech-niques. Moreover for the machines with EarthPressure Balance the support pressure mediumshould have higher density and viscosity.In the EPBs the tunnel face support is provideddirectly by the excavation material. This on onehand creates some limitations for soil propertiesin which EPBs can be applied. The ideal soilshould have soft to stiff plastic consistency orbe easily converted to mass of this kind. Thefraction of fine-grained materials (smaller then0,06 mm) has a substantial influence and shouldnot be smaller then 30%. On the other hand theapplication area of EPBs can be expended by theuse of soil conditioners, such as bentonite, poly-mers or foam. It is important to mention thatin coarse-grained and mix-grained soil types aswell as in hard rock along with increase of facesupport pressure there is a disproportional in-crease in face contact force and torque. Thiscan lead to the substantial increase in energy de-mand.

Due to the structural similarities between thepresented close systems TBMs, in practice thereare examples of machines, which can be relat-ively easily transformed from one type to an-other, depending on the anticipated geologicalconditions. These are however not presentedamong the projects considered in the frame-work of this research.

2.2 Energy Efficiency of Tunnel BoringMachines

In order to discuss EE of TBMs the basic designelements should be discussed. These include:cutting wheel, cutting wheel carrier with thecutting wheel drive motors, the machine frame,as well as the clamping and driving equipment.The control facility and auxiliary equipmentare usually connected to this construction onone or more trailers. (Maidl et al., 2008)The main system groups featured in a TBM arepresented on the figure 10 and include (Maidlet al., 2008):- Boring system (denoted with 1);- Thrust and clamping system (denoted with 2);- Muck removal system (denoted with 3);- Support system (denoted with 4).

2.2.1 Boring system

The boring system is the most important part,determining the performance of a TBM. Mainelements of the boring system are the cutterhousings with disc cutters mounted on a cut-ter head (also known as cutting wheel). Cuttingwheels can be designed in various ways in orderto better fit the geological conditions and im-

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Figure 11: Main cutter head construction elements. Source: Maidl et al. (2008).

prove performance rates. Thus the spatial dis-tribution of the disc cutters, reamers and muckremoval buckets, as well as size and amount ofthese elements generally depend on the geolo-gical conditions, in which the machine is inten-ded to operate. (Maidl et al., 2008)Main cutter head construction elements are de-picted on the figure 11. Disk cutters are usedto exert pressure on the rock material causingits breaking. Because the disc cutters to vari-ous extent exposed to wearing, these are moun-ted on special housing, which enables more ef-fective replacement of the worn cutters on thecutter head. The excavated muck is then collec-ted through the buckets (Maidl et al., 2008). Onthe TBMs operating in fractured soft rock andsoils further excavation tools such as scrapers,drag picks, flat and round chisels and rippersare mounted onto the cutter head (Maidl et al.,2012).

2.2.2 Thrust and clamping system

Thrust and clamping system also influences theperformance of a TBM. The total thrust cre-ating the necessary cutting wheel loadings andcounteracting the friction forces from the shieldof the machine (which depend on its type) isto be provided, in order to enable sufficientpenetration rate during the tunnel advance pro-cess. Hydraulic cylinders a TBM is equippedwith create the required pressure. The length of

the piston of the thrust cylinder determines themaximum stroke, or the length of one advancestep. (Maidl et al., 2008)

The schematic design of a single gripper clamp-ing system developed by Herrenknecht AG isdemonstrated on the figure 12. It shows the po-sition of gripper units and propulsion cylindersin relation to the other parts of the TBM.

Clamping system is used in order to exert thetotal thrust forces axially either directly to thetunnel walls (Gripper TBM, Fig. 12), whichrequires a very good (stable) rock to be boredthrough, or to the previously installed tunnelsupport, built of reinforced segments. The lat-ter must have the capacity to withstand the totalthrust forces. The number of the segments gen-erally depends on the diameter of the tunnel.

The tunnel advance process can be divided intotwo main stages with respect to function of thethrust and clamping system. During the firststage (the boring process) the clamping units arepushed against the tunnel walls or the tunnelsupport, rotating cutter head is pressed againstthe tunnel face. This stage continues until thelimit of the thrust cylinder pistol length limit isreached. During the second stage the clampingunits are loosened, moved to the new positionand braced against the tunnel walls again. Thetunnel support if at all is generally built duringthis stage as well.

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Figure 12: TBM with single gripper clamping system (Main Beam TBM S-167 by Herrenknecht, ø9.43). Source: Maidl et al. (2008).

2.2.3 Muck removal systemThe removal of the excavated materials is an im-portant task, which has to be fulfilled continu-ously in order to prevent idle times during thetunnel construction. The muck removal startsfrom the tunnel face and continues up to abovethe ground level. In Hardrock TBMs materialtransportation starts with buckets, which col-lect the excavated muck and transport it to theconveyor. In case of Earth Pressure BalanceSupport TBMs the high-density muck is re-moved from the excavation chamber by a screwconveyor (Fig. 13). In Mixshield TBMs low-density material is transported by slurry pump.Thus transportation method used is highly de-pendant on the properties of the excavated ma-terial. (Maidl et al., 2012)Moreover energy consumption strongly de-pends on the transportation method in use, e.g.screw conveyors and slurry pumps belong tothe main energy consumers on the respectiveTBM types.There are various types of material transportsystems through the tunnel, which in generalcan be divided into two main groups: opentransport and piped transport (Maidl et al.,2012).Open transport is mainly suitable for the trans-portation of hard rock material, dry material orhigh-density slurry. The nowadays most com-monly used open transport type is belt con-

veyor. This technology has developed to a highlevel, allowing for example to even operate intunnels up to 6 km long and with curves. Otheropen transport techniques include rail trans-portation systems (mainly suitable for large dia-meter tunnels), and muck cars. (Maidl et al.,2008), (Maidl et al., 2012)Piped transport is generally used on MixshieldTBMs. It is suitable for low-density materialtransportation, since in this method the muckis pumped out from the excavation chamber toabove the ground level, where the slurry goesthrough a special treatment process. Duringthis process excavated sludge is removed and theconditioner, e.g. water, can be reused. (Maidlet al., 2012)

2.2.4 Support systemThe support system of a TBM is used in orderto install tunnel lining. The role of the tunnellining is to secure structural safety, durabilityand serviceability for the entire period of tun-

Figure 13: Screw with and without centralshaft. Source: Maidl et al. (2012).

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Figure 14: Installation of crown arch sup-port with mesh reinforcement and anchor drill.Source: Maidl et al. (2008).

nel life (Maidl et al., 2012). There are varioustypes of lining, including grouting, installationof anchors, steel arches, steel rings, meshes or acombination of these (Fig. 14), as well as linerplates and segmental lining.The type of lining required strongly dependson the quality of the rock the tunnel is be-ing advanced through. Here a parameter calledstand-up time is of the highest importance. Ingeological conditions with long stand-up time,generally low fractured and non-weathered hardrock, none or minor lining, such as grouting,needs to be installed. In case of highly frac-tured hard and soft rock, where rock falling isto be expected the installation of anchors oftenin combination with meshes and steel arches orsteel rings is required. In highly fractured rockwith high water content the installation of seg-mental lining is preferable in order to secure thetunnel and avoid decrease of groundwater levelhaving highly negative environmental impact aswell as negative impact on above ground con-structions due to subsidence. In soils with orwithout water content the installation of seg-ment lining is inevitable in order to secure sta-bility of the tunnel and avoid water inflow.The design and constructional features of aTBM are rather complicated and cannot becovered within this report. Thus by interestoriginal sources, mainly Maidl et al. (2008) andMaidl et al. (2012) should be referred to.

2.2.5 Research trendsGenerally one can state that over the periodof TBM technology development many stud-

ies were (and still are) focusing on the improve-ment of TBM performance, especially with re-spect to the boring process (Bilgin et al., 2012).Other researches implemented in this area in-clude e.g. investigation of correlations betweenvarious geotechnical properties of the rock andthe applied machinery, in order to predict theperformance of a TBM in various geological en-vironments and to secure a better fit betweenthese two (Nishioka et al., 1997), (Zhao et al.,2007), (Balci, 2009), (Hassanpour et al., 2010). Anumber of computational models were createdfor this purpose (Acaroglu et al., 2008).

At the same time little attention seems to bepaid to the EE issues when it comes to TBMequipment. One of the possible reasons isthe still relatively low energy expenses espe-cially when compared with the overall costs ofthe tunnel construction projects, as was men-tioned before. Another reason, which some-how originates from the first, is the difficultyin motivating clients to purchase machines withlower capacities. However the lack of publishedmaterials on this subject should not necessarymean that no work is being done in this field.Taking into consideration the growing globalconcerns regarding EE one can assume that theTBM producers are conducting some researchactivities in this area, but their results are notpublicly available.

EE with regard to TBMs is a very wide andcomplex topic, which has to deal with widerange of issues, such as geological and hydro-geological and geotechnical influence, techno-logical influence and influence of driving ap-proach of the TBM crew. Another problem-atic issue, which is worth mentioning here,is the widespread re-use of sometimes energyinefficient or not particularly suitable in EEsense equipment pieces (e.g. main distributionboards of higher capacity then required, inef-ficient slurry pumps). And whereas the re-usedoes make (environmental) sense, this practisesometimes leads to the construction of over-powered TBMs with higher energy consump-tion then necessary. Taking into considerationthe complexity of the topic, tons of high qualitydata (including energy consumption logs, geo-technical information including high-resolutiongeology profiles, reliable information on layoutof the machines as well as the conditions un-

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der which these operate, e.g. electricity supplycharacteristics) need to be analysed in order toachieve solid and reliable results.

2.3 Environmental impact andEuropean legal framework

2.3.1 Energy Efficiency and Energy Conser-vation

According to (Croucher, 2011) there is a dis-tinct difference between terms Energy Effi-ciency (EE) and Energy Conservation (EC). EEgenerally focuses on adjusting directly input re-quirements (electricity) for a given output de-cision (goods and services) with the aim to re-duce the energy demands of electricity intens-ive production or utilisation process. EC onthe other hand focuses on reducing the overalloutput decisions, leading to reduction of the re-quired amount of energy. An example of ECis switching of the light, when it is not needed.Both of the practices strive to achieve the samegoal of rationalised energy consumption andtherefore are closely related.Over 40 years ago with the oil crisis in 1970sthe policy-makers in many industrialised coun-tries demonstrated understanding of the ne-cessity in efficient use of energy by givingpriority to the subject (Chai & Yeo, 2012).Nowadays efficient use of energy is a must anda very hot topic, spiced by scarcity of fossilfuels, limitations of natural resources and a vari-ety of environmental issues associated amongothers with energy production and utilisation.The parallelism between energy consumption

1980 1985 1990 1995 2000 2005 2010 20151.5

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Figure 15: Total CO2 emission from energyconsumption vs. total primary energy con-sumption. Data source: U.S. Energy Inform-ation Administration, 2011.

Nuclear, 12.96%

Hydroelectric, 16.82%

Geothermal, 0.33%

Wind, 1.69%

Solar, Tide and Wave, 0.15%

Biomass and Waste, 1.55%

Total Conven+onal Thermal, 66.62%

Hydroelectric Pumped Storage,

-‐0.11%

Worldwide electricity net genera+on by type (2010)

Figure 16: Worldwide electricity net genera-tion by type as for 2010. Data source: U.S.Energy Information Administration, 2011.

and carbon emissions denoted by (Linares &Labandeira, 2010) for the industrialised coun-tries from 1990-2007 is also notable when plot-ting worldwide data for the period 1980-2011 ac-quired from (U.S. Energy Information Admin-istration, 2011) (Fig. 15).Current electricity production is among oth-ers very dependant on fossil fuels, especiallycoal and gas. Over 65% of electricity generatedglobally originates from conventional thermalpower plants (Fig. 16 ), requiring fossil fuelsin order to generate heat and produce steam,which drives the turbine allowing to generateelectricity.According to (McLean-Conner, 2009) successfulimplementation of EE provides following bene-fits:

• Lower energy costs (the less energy is util-ised the lower are the energy bills coupledwith a better control and understanding ofenergy usage patterns on the side of thecostumer);

• Cost-effective investment (investments inEE have impact on the future costs of en-ergy);

• Fast and significant energy savings (as a res-ult of EE implementation);

• Environmental benefits (reduction of en-ergy consumption decreases the anthropo-logical stress exerted on the natural sys-tems);

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• Faster economic development (e.g. morecompetitive position of companies invest-ing in EE, creation of new jobs in EE sec-tor).

However despite steady progress in the tech-nical efficiency the global energy consumptioncontinues to increase (Moriarty & Honnery,2012). This phenomenon could be partiallyexplained by the constant population growthleading to increasing energy demand. Anotherimportant reason is relatively low penetrationrate of seemingly cost-effective EE technologies,which is described in EE literature as EE gap(Croucher, 2011).According to (Croucher, 2011) EE gap can beexplained by the following reasons:

• Additional investments (implied when re-placing less energy efficient technologicalsolution with a better one);

• Higher discount rates of the customers(when calculating net present value of agiven option);

• Lack of information (customers do nothave sufficient information about EE fea-tures of the products);

• Loss aversion (customers are more satisfiedwhen saving at purchase then when expect-ing gain from reduced energy costs);

• Liquidity constraints (lack of access tocredit markets or high interest rates of thebanks);

• Principal-agent problem (one group makesthe investment decision and another ac-quires benefits).

In order to achieve the benefits of EE the abovenamed barriers need to be dealt with by ap-plying specific means, e.g. investing in devel-opment or purchase of more energy efficienttechnologies, clearly demonstrating the advant-ages of EE products, making necessary inform-ation available for the clients preferably in theirnative language and close interaction with thecustomers, partners and other stakeholders, act-ively promoting EE solutions.Moreover organisations advocating EE prin-ciples can be contacted and implicated into the

implementation process for the new energy ef-ficient products in order to secure effective co-operation, public relations, promotion and lob-bying among the respective stakeholders, aswell as proper labelling of the EE products.The EE gap, its barriers and limitations aswell as principles and practices to overcomethese and promote EE solutions are furtherdiscussed in McLean-Conner (2009), Linares& Labandeira (2010), Chai & Yeo (2012) andCroucher (2011).

2.3.2 Legal framework in EuropeEnergy is an important commodity for exist-ence and development of any country or re-gion. European Union as one of the most pro-gressive parts of the world is not an exception.Most of the energy consumed in EU today isbeing imported from other locations. Rapidlygrowing prices for energy sources along with in-creasing emissions of carbon dioxide and otherGHGs pushing forward the already progressingclimate change have created the conditions inwhich counteraction is inevitable (Capros et al.,2011).As a result wide range of legal documents andpolicies was adopted, including Action Planfor EE (2007-12), Ecodesign for energy-usingappliances 2009/125/EC, Promotion of the useof energy from renewable sources 2009/28/EC,Product energy consumption: Informationand labelling 2010/30/EU, EUROPE 2020: Astrategy for smart, sustainable and inclusivegrowth (2010), EE Plan 2011 and EE Directive2012/27/EU to name a few. The full assessmentof legal framework for EE in European Unionis beyond the scope of this paper. Only EE Plan2011 as the most relevant document to the fieldof this study is presented and shortly discussedbelow. In order to avoid misinterpretationof EE Plan 2011 the further text generallyrepresents copied bits from the original paper.

EE Plan 2011The EE Plan passed by the European Commis-sion in 2011 is a supplement for the Europe2020 Strategy and is meant to assist in realisa-tion of the strategy with regard to EE concept,its targets and practices, as described in thestrategy.According to the (Commission, 2011) ’EEmeasures will be implemented as part of the

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EU’s wider resource efficiency goal encom-passing efficient use of all natural resourcesand ensuring high standards of environmentalprotection’.

Buildings and constructions’The greatest energy saving potential lies inbuildings. The plan focuses on instruments totrigger the renovation process in public andprivate buildings and to improve the energyperformance of the components and appliancesused in them. It promotes the exemplary roleof the public sector, proposing to accelerate therefurbishment rate of public buildings througha binding target and to introduce EE criteria inpublic spending. It also foresees obligations forutilities to enable their customers to cut theirenergy consumption’ (Commission, 2011).

Transportation’Transport has the second largest potential.This issue is addressed by the White Paperon Transport (2011), seeking to develop acompetitive and resource efficient transportsystem throughout European Union. TheWhite Paper on Transport defines a strategy forimproving the efficiency of the transport sectorthat includes e.g. the introduction of advancedtraffic management systems in all modes,infrastructure investment and the creation ofa Single European Transport Area to promotemultimodal transport’ (Commission, 2011).

Industry’About 20% of the EU’s primary energy con-sumption is accounted for by industry. EE inindustry will be tackled through EE require-ments for industrial equipment, improved in-formation provision and development of appro-priate incentives for SMEs, measures to intro-duce energy audits and incentives to introduceenergy management systems for large compan-ies’ (Commission, 2011).’Building on the success of ecodesign meas-ures as an effective tool to stimulate innov-ation in energy efficient European technolo-gies, the Commission is investigating whetherand which energy performance (ecodesign) re-quirements would be suitable for standard in-dustrial equipment such as industrial motors,large pumps, compressed air, drying, melting,

casting, distillation and furnaces’ (Commission,2011).Moreover ’in order to support technologicalinnovation, the Commission will continue tofoster the development, testing and deploymentof new energy-efficient technologies’ (Commis-sion, 2011).’Improvements to the energy performance ofdevices used by consumers - such as appliancesand smart meters - should play a greater rolein monitoring or optimising their energy con-sumption, allowing for possible cost savings. Tothis end the Commission will ensure that con-sumer interests are properly taken into accountin technical work on labelling, energy saving in-formation, metering and the use of ICT’ (Com-mission, 2011).

3 METHODOLOGY

In this research the total number of 39 tun-nelling projects conducted with HerrenknechtAG machinery were analysed. This includes19 Earth Pressure Balance Support TBMs, 15hardrock machines (including Gripper TBM,Single Shield TBM and Double Shield TBM)and 5 Mixshield TBMs. Moreover the resultsof analysis conducted by Benedikt Broda, whichincluded 24 projects: 13 Earth Pressure SupportTBMs, 8 Mixshield TBMs and 3 Gripper TBMs,are also included in this research.A number of various electronic solutions fordata and information storage as well as for dataanalysis have been used. These are more in de-tail described in the respective sections below.

3.1 Data analysis software

In order to effectively conduct calculations andanalysis of the available data software productswere used. These mainly include Matlab andExcel.

3.2 Data analysis

The data analysis encompassed various stepsfrom pre-analysis or the data quality assessmentas described above to a number of calculations,generalisations, statistical tests as well as graph-ical visualisations. These data manipulations aredescribed in detail in the respective subsectionsbelow.

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3.2.1 Calculation of the active powerEnergy flow in a system can be described withthe following terms: active power, whichis the useful power producing work (heat,motion etc.), reactive power, which does nottransfer energy and represents energy losses,and complex power, which is a sum vector ofthe previous two. The minimisation of lossesdue to reactive power is out of the scope ofthis research. The actual useful power vector,known as active power, is considered as anindicator. Active power is used to calculatepower utilisation and energy consumption asdescribed in sections 3.4.2. Power utilisationand 3.4.3. Energy consumption respectively.

Cutting wheelThe equation used for calculation of the activepower is derived from general equation for thecalculation of power:

P = τ ∗ ω (1)

where τ is torque and ω is angular velocity ofthe rotating object.Since instead of angular velocity expressed inradians per time unit, rotational speed (ω) ex-pressed in rotations per minute is used, the rightside of the Eq. 1 is multiplied with 2π. Thetorque is usually expressed in [MNm]. In orderto acquire active power in [kW ] a conversionfactor is added as well (Eq. 2).

Pcw = 2π ∗ τ ∗ ω ∗ 1000/60 (2)

Screw conveyorScrew conveyors belong to the main energyconsumers on the Earth Pressure Balance Sup-port TBMs. An equation similar to Eq. 2is used for the calculation of the active powerfor screw conveyor. The torque is usually ex-pressed in [KNm]. Thus the conversion factoris slightly different (Eq. 3). As a result the unitfor active power is also [kW ].

Psc =2π ∗ τ ∗ ω

60(3)

PumpsSlurry pumps are often main energy consumerson the Mixshield TBMs. The active power ofthe slurry pumps is calculated using the Eq. 4:

Psp =Q ∗ PEF

∗ 100

3600(4)

where Q is the flow rate expressed in[m3/hour], P is the pipeline pressure expressedin bar, and EF is the pump specific efficiencyfactor obtained from pump performance curve(Fig. 17). The last term in the equation is theconversion factor added in order to obtain theresult in [kW ].

3.2.2 Power utilisationPower utilisation analysis is an important partof this research, which was conducted in or-der to determine the adequacy of the installedpower capacities. The power utilisation is as-sessed as mean and maximum utilisation and iscalculated for all main consumers of the TBMsof concern.Mean power utilisation is the relation betweenthe mean active power over the advance processand the installed capacity of the respective con-sumer (Eq. 5). The mean power is calculatedfrom the current values by integration of act-ive power dataset over the entire project periodusing integration functionality in Matlab. Theresult was then divided by time in order to ob-tain mean values in [kW ]. The stops duringthe construction were excluded from the ana-lysis.

Umean =Pmean

Pinstalled(5)

Maximum power utilisation is, on the otherhand, the relation between the maximum activepower and the installed capacity of the respect-ive consumer (Eq. 6). The maximum value foractive power in each dataset was identified witha special Matlab command.

Umax =Pmax

Pinstalled(6)

The reserve (R) is the percentage of the installedpower, which is not in use. The reserve is calcu-lated with following simple equation:

R = 1− U (7)

The reserve is used in order to prepare mean-ingful pie charts, demonstrating the mean andmaximum utilisation for the main consumers ineach individual project.

16


Figure 17: Application of pump performance efficiency curve.

3.2.3 Energy consumptionEnergy consumption analysis is another im-portant part of the research project. It was con-ducted in order to compare energy consump-tion between different TBM types with variousdiameters.In order to calculate the energy consumptionper unit volume [m3], the volume per ring hasto be calculated. The following equation is usedfor this purpose:

Vring = r2 ∗ π ∗ Segmentlength (8)

In case of Gripper TBMs, where segmental lin-ing is not constructed, a modification of this for-mula is used:

Vring = r2 ∗ π ∗ Tunnelmeter (9)

Energy consumption per excavated volume isthe most unified and meaningful result for com-parison of energy consumption between differ-ent machine types. Eq. 10 is used to calculatethe energy consumption per excavated volume(Em):

Em =P ∗ t

V ∗ 3600(10)

where P is the mean active power, t is the meanadvance time, and V is the volume of one ring,calculated in the previous step.

Energy consumption per ring is rather subject-ive value due to the variation in diameters andslight variation in segmental lengths betweenthe projects. Eq. 11 was used in order to cal-culate the energy consumption per ring (Er).

Er =P ∗ t3600

(11)

In addition active power per excavated volumefor both MDB and cutting wheel was calculatedusing Eq. 12 demonstrated below.

Pm =P

V(12)

3.2.4 Exploratory Data Analysis

Statistical data analysis provides means to bet-ter understand the data. There are two generalways to accomplish this task: through visualisa-tion and more formal statistical methods. Ex-ploratory Data Analysis implies the visualisa-tion of large and cumbersome data into easilyunderstandable graphical displays. (Reimannet al., 2011)The tools of EDA were among others imple-mented within this research, in which variousgraphical data representations were prepared inorder to explore the data itself and the correla-tions between different datasets. These includee.g. histograms, various distribution functionplots, boxplots and their various combinations.

17


According to Reimann et al. (2011) even ingraphical data analysis mathematical data trans-formations are necessary in order to providebetter visibility. A typical example is logar-ithmic transformation, which is aimed at inclu-sion of unusually high or low values. The log-arithmic transformation is e.g. used in the box-plots.

3.2.5 Ansari-Bradley test

F-test is applied to compare the variance of twodifferent datasets. A normal F-test requires nor-mal distribution and independent samples inboth tested datasets (Reimann et al., 2011). Tak-ing into consideration the fact that the data en-countered in this research is generally not nor-mally distributed a non-parametric modifica-tion of the F-test is necessary.

Ansari-Bradley test is a non-parametric versionof the F-test, developed by Ansari and Bradleyin 1960. It only requires independent samplesin the tested groups. Based on the derived p-value a conclusion about the equality of vari-ances of the tested datasets can be made. It isimportant to mention that p-value representsprobability and significance level is the prob-ability that the null hypothesis, although beingcorrect, is wrongly rejected (usually significancelevel is 0.05, or 5%). In case p-value is smallerthan the chosen significance level, the null hy-pothesis of the test is rejected. (Reimann et al.,2011)

3.2.6 Kruskal-Wallis test

T-test is appropriate for comparison of the cent-ral values of several datasets. It requires inde-pendent and normally distributed data in eachgroup, as well as equal variances for all groups(Reimann et al., 2011). For the same reasonstated in the previous section, a non-parametricversion of T-test is necessary.

Kruskal-Wallis test is a non-parametric versionof T-test, developed by Kruskal and Wallis in1952. The requirements of the test are inde-pendence of the data in the groups and continu-ous distribution in each tested dataset (Reimannet al., 2011). The resulting p-value can be usedto either support or reject the null-hypothesisas described in the previous section for Ansari-Bradley test.

4 DATA

This research encompassed a wide range of dataoriginating from various sources. The data in-cludes energy consumption logs, general geo-technical information in some cases accompan-ied with detailed geological profiles, informa-tion on machinery design features, and vari-ous project specifications. This section is intro-duced in order to provide the reader with anoverview over the data used, characterise themain data sources and in case of energy con-sumption logs present the results of data integ-rity and quality assessment.

4.1 Geotechnical informationThere are several phenomena having a strongnegative effect on energy consumption of aTBM. These generally include primary and sec-ondary wear of excavation tools and clogging.Both of these phenomena decrease the effective-ness of TBM application by deteriorating the ef-ficiency of muck excavation and transportationtools and increasing idle times required for re-pair or removal of the excavation material fromclogged machinery parts.The key rock and soil characteristics relevantfor the energy consumption assessment include:

• Rock quality (RQD or Rock QualityDesignation Index, RMR or Rock MassRating, UCS or Uniaxial CompressiveStrength, and UTS or Uniaxial TensileStrength) describing the strength and de-gradability of the rock mass;

• Abrasivity (CAI or Cerchar Abrasivity In-dex), causing the wear of excavation tools(e.g. disc-cutters, cutter head, screw con-veyor);

• Clay content (adhesion, cohesion, dens-ity, hydraulic conductivity) indicating theclogging problem potential.

The information presented here representsshort summaries from geotechnical reports ofthe respective projects with the focus on themost influential parameters, as described above.The only exception is the project C-2, wherealong with summarised geotechnical reports amore detailed description of geologies based onthe available geological profiles is used. The

18


Table 1: Tunnel specifications A-4.

TBM type Single ShieldLength tunnel trace 4840 mTunnel diameter (exc.) 9.36 mMin radius of the trace 2000 mMax/min gradient 0.54%Max cover crown ∼ 1700 mMin cover crown ∼ 700 m

projects had undergone anonymisation proced-ure, as a result A stands for Hardrock TBM, B -for EPB TBM and C - for Mixshield machines.Not all of the relevant parameters are availablefor the presented projects, thus the projects donot have a unified geotechnical descriptions.A-4Limy Schists containing alternating contents ofmarble and phyllites predominantly representthe geology. This formation covers approxim-ately 99% of the tunnel trace. Ca. 1% ofthe trace is located in massive anhydrite. Bothformations are almost impermeable. Only littlewater inflow can be expected. Depending onthe ice coverage of the mountains and long rain-fall periods, inflow of 30 to 60 [l/s] in faultzones is possible. Maximum UCS of forma-tion a is up to 150 [MPa], of formation b - upto 60 [MPa]. With CAI values between 1 and2 the formations can be characterised as me-dium abrasive. Further details can be found inAppendix I.Mineral composition of the limy Schist includes65% calcite, 15%, 10% of muscovite and chlor-ite, as well as accessory albite, zoisite, epidote,pyrite and graphite.For statements about the swelling pressures andtendency to adhesion a more detailed invest-igation is required. Further geological risksinclude: high convergences between 2850 and4150 [m] (up to 45 [cm]), rock burst possiblebetween 2850 [m] and the end of the tunneltrace, rack fall after 3350 [m], water inrush at150 [m], fault zones at different points as well ashealth threatening gases hydrogen sulphide andradon along the entire trace. For tunnel spe-cifications please refer to Table 1.B-16Geology is generally presented by cohesiveformations like clay, silty clay, as well as clayeyand silty sand. Very little information is avail-

Table 2: Tunnel specifications B-16.

TBM type EPBLength tunnel trace 8120 mTunnel diameter (exc.) 4.94 mMin radius of the trace ∼ 1000 mMax/min gradient 0.11%Max cover bottom ∼ 35 mMin cover bottom ∼ 10 m

able about the rock quality, rock strength andabrasiveness. According to the informationfrom the customer the max UCS of the rockis 80 to 100 [MPa]. Some further details can befound in Appendix II.Since there is no information on abrasiveness(e.g. CAI), no assessment of wearing is possible.In the clay and silt section abrasivity shouldnot be important. In the sandstone section therock is more abrasive (estimated CAI of 2.5to 4), thus secondary wear in screw conveyorshould be expected in those areas. Maximumwater level at invert in soil section is ∼25 [m],with maximum water pressure at this level of2.5 [bar]. Being mainly excavated in clays ofhigh plasticity, clogging may represent a prob-lem. During the tunnel construction maximumground settlement allowed was 50 [mm]. Fortunnel specifications please refer to Table 2.C-2The geology of the area originates from qua-ternary and tertiary and is represented predom-inantly by mica-rich silt and clay with local en-claves of mica-rich sands. Ground moraine andsands also significantly influence the geologicalconditions in the area. Further details can befound in Appendix III.Bedding of the soils can be estimated assemisolid to solid. Consistency is soft to solid.Due to availability of highly cohesive mater-

Table 3: Tunnel specifications C-2.

TBM type MixshieldLength tunnel trace 2 x 2811 mTunnel diameter (exc.) 6.3 mMin radius of the trace 300 mMax gradient +5.0%Min gradient + 0.1%Max water pressure (invert) ∼ 3.5 barMax cover crown ∼ 32 m

19


ials (mica-rich silts and clays) there is a highprobability of clogging. Moreover high wearrate is expected, caused by abrasive till compon-ents, hard magmatic plutonic rocks and meta-morphic rocks in form of erratic blocks andboulders (e.g. granite, diorite and gneiss).Both parallel tunnel traces were bored in thesame direction. For tunnel specifications pleaserefer to Table 3.Based on the geological profiles the main sec-tions with relatively unified geological condi-tions are identified and demonstrated in theAppendix IV. The cross-sections represent gen-eralised and interpolated information fromtaken samples. Colours represent the expec-ted energy demand from more energy intensiveconditions (darker tints) to less energy intensiveconditions (lighter tints). This classification isvery generalised and subjective and thus shouldbe used for basic orientation only.The sections with similar and different geolo-gies are compared in terms of TBM energy con-sumption using Ansari-Bradley and Kruskal-Wallis tests.

4.2 Energy consumption data assess-ment

The quality of the data selected for the researchwas given high priority. In total 15 hardrockTBMs, 19 EPB TBMs and 5 Mixshield TBMswere preselected. In order to secure requiredlevel of data quality, data check was conducted.The datasets required for the EE analysis areTBM type specific. In the framework of theproject all of the collected datasets were invest-igated in order to assess their quality with focuson data integrity and plausibility. As a result ofthis procedure a significant number of projectswere rejected from further analysis due to baddata quality: systematic error, significant gapsin data or complete absence of the required data.Random data error in form of spikes has alsobeen identified in some projects. In cases wherespikes were significant they were removed fromthe datasets.

4.3 Additional sourcesAdditional sources of information used in thisresearch are:

• Power lists containing information aboutthe equipment installed on a TBM (used toidentify main energy consumers);

• Pump efficiency curves (used to acquiremean efficiency factor of the pumps forMixshield TBM projects);

• Electric schemes were used to identify en-ergy sources of the main energy consumers(MDB1, MDB2 etc.).

5 RESULTS

Only part of the analysed projects is presen-ted here due to KTH/LWR restrictions for themaximum number of pages in a master thesisproject. In the summary sections as well as inDiscussion all analysed projects are presentedand discussed. Conclusions also cover all invest-igated machines.

5.1 EDA Analysis of Hardrock TBMA-4

A large gap in logged data occurs from approx-imately the middle of the project implement-ation time. There are multiple idle periodsduring the tunnel advance process (Fig. 18)expressed through a "comb-like" shape of theplot. During the idle periods energy is beingconsumed at lower rates (0 to 500 [kW]). Atthe end of the project period the tunnel ad-vance becomes more intensive, which is indic-ated through more active cutting wheel opera-tion.

7.347 7.348 7.349 7.35 7.351 7.352

x 105

0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

P [kW

]

Time [Serial Date Number]

MDB total active power

Cutting wheel active power

Figure 18: MDB total vs. cutting wheel activepower from A-4.

20


0 500 1000 1500 2000 2500 3000 3500 4000 4500

1

2

3

4

5

6

x 105

P [kW]

Fre

quency [−

]


Figure 19: Histogram of MDB total activepower from A-4.

The high amount of values within the range0 to 500 [kW] is also evidenced in figure 19.77.4% of the values lie within this range. Atthe same time median and mean of the cuttingwheel active power are 2157.1 and 1727.7 [kW]respectively. Thus most of the values within therange 0 to 500 [kW] are not associated with cut-ting wheel operation and might represent idlerunning muck transportation conveyor, light-ing or operation of other minor consumers. Acloser look at the distribution of loads amongMDBs (Fig. 20, Fig. 21) allows further interest-ing observations. The MDB1 is loaded to onlyhalf of its full capacity, which is 2200 [kVA] (or1980 [kW], assumed power factor value is 0.9,acquired from HK AG).MDB2 and MDB3, responsible for powersupply for equal amount of cutting wheel

100 200 300 400 500 600 700 800 900 10000

0.5

1

1.5

2

2.5

3

3.5

4

x 105

P [kW]

Fre

quency [−

]

MDB1 active power

Figure 20: Histogram of MDB1 active powerfrom A-4.

Figure 21: Histogram of MDB2 and MDB3 act-ive power from A-4.

drives, show very similar patterns. BothMDBs also have similar maximum loads(2000±50 [kW]), which do not reach their fullcapacity (2800 [kVA] or 2520 [kW]). The highamount of values beyond 500 kW is character-istic for both MDBs. The results of Ansari-Bradley and Kruskal-Wallis tests also revealsome similarity between these two sets (p=6.9e-142 and p=3.4e-108 respectively), however theextremely small p values suggest rather a verygeneral similarity.

The box plot (Fig. 22) confirms the featuresidentified from previous figures and suggestsfurther observations. Sample medians (red linesin the boxes) of MDB2 and MDB3 are very close(900±15 [kW]). The medians are not centred inthe box, which shows samples’ skewness. Out-liers (red crosses) are characteristic for MDB1.However these probably represent correct val-

21


0

500

1000

1500

2000

2500

MDB1 MDB2 MDB3

P [kW

]

Figure 22: Box plot of MDB1, MDB2 andMDB3 active power variations from A-4.

ues, since they lie within the capacity range ofMDB1.Figure 23 shows a clear positive correlationbetween the active power of the cutting wheeland advance speed of the TBM.

5.2 EDA Analysis of EPB TBMB-16Figure 24 demonstrates the distribution of val-ues logged on MDB during the tunnel advanceprocess. The maximum capacity of the MDBis 1500 [kVA] or ca. 1350 [kW], whereas max-imum utilised capacity is 850±25 [kW]. Asone can see many values lie within range 0 to200 [kW] (68.1%), whereas the most frequentrange is 75 to 100 [kW] (13.9%).Figure 25 demonstrates the total active powerof the MDB against the active powers of the

Figure 23: Active power of the cutting wheelvs. advance speed from A-4.

0 100 200 300 400 500 600 700 800 900

1

2

3

4

5

6

7

8

x 105

P [kW]

Fre

quency [−

]

MDB active power

Figure 24: Histogram of MDB total activepower from B-16.

main consumers. There is a gap in the loggeddata from 22-01-2012 (734890 Serial Date Num-ber) to 02-03-2012 (734930 Serial Date Num-ber). Based on the advance ring number, notunnel advance has taken place during this stage.Right before this idle period the screw conveyorenergy consumption becomes steady and veryhigh (275±25 [kW]), whereas the maximum ca-pacity of the screw conveyor is 132 [kW].On a zoomed-in version of this section of thegraph (Fig. 26) one can see that the frequentoverloads of the screw conveyor is a constantfeature from 14-09-2011 to 22-01-2012 (the startof the idle period).The box plots demonstrated on the figure 27show the interquartile ranges of the act-ive power logged on the cutting wheel andthe screw conveyor. The graph suggeststhat the interquartile range of the cutting

7.3465 7.347 7.3475 7.348 7.3485 7.349 7.3495 7.35 7.3505 7.351

x 105

0

200

400

600

800

1000

1200


P [kW

]



Screw conveyor active power

Figure 25: MDB total active power vs. mainconsumers from B-16.

22


7.3483 7.3483 7.3483 7.3483 7.3483 7.3483 7.3483 7.3483

x 105

100

200

300

400

500

600

700


P [kW

]



Screw conveyor active power

Figure 26: MDB total active power vs. mainconsumers from B-16 (zoomed-in).

wheel active power is from 100±15 [kW] to180±15 [kW], whereas this for screw conveyoris from 0±5 [kW] to 80±10 [kW]. The out-liers marked as red crosses on the graph liewithin 700±25 [kW] for the cutting wheel(which is within its maximum capacity) andfrom 200±15 [kW] to 310±10 [kW] for thescrew conveyor (which is far beyond its max-imum capacity). The upper 25% of the val-ues for active power of the screw conveyor arepartly within and partly beyond the capacity ofthe equipment (80±10 [kW] to 200±5 [kW]).

5.3 EDA Analysis of Mixshield TBMC-2Figure 28 demonstrates the overall active powerflows and advance ring number during the pro-

0

100

200

300

400

500

600

700

Pcw Psc

P [kW

]

Figure 27: Box plot of cutting wheel activepower vs. screw conveyor active power fromB-16.

Figure 28: Plots of MDB active power vs.slurry pump active power, cutting wheel act-ive power and advance ring number over timefrom C-2 on trace#1 (above) and on trace#2(below).

ject C-2 on trace#1 and trace#2. As figuresuggests there are more long-term stops dur-ing the construction of trace#1. Based on thedocumentation slurry pump installed on themachine has higher power capacity (723 [kW])than cutting wheel (75 [kW] x 6 or 450 [kW]),which is also obvious from the graphs.Figure 29 reveals similarities between MDB act-ive power distributions from both traces. Theshares of the values in the range 25 to 200 [kW]are relatively similar for both traces and repres-ent some 22%. Trace#1 also contains largeramount of 0 values than the trace#2, which arenot depicted on the histogram.Figure 31 illustrates the comparison of activepower variations on the cutting wheel betweentrace#1 and trace#2. Trace#1 has a longerset of values, and smaller median active power(32 [kW] against 92.6 [kW] in trace#2). Thus

23


Figure 29: Histogram of MDB active powerfrom C-2: trace#1 (above) and trace#2 (be-low).

tunnel advance process was longer but withsmaller active power per unit time during theadvance of the trace#1. The interquartile rangefor the cutting wheel active power in trace#1lies within range 0 to 140±5 [kW], in trace#2 -0 to 160±5 [kW]. The furthest outliers withinboth traces lie slightly above the maximum ca-pacity.

The comparison of active power of the slurrypump on the two traces is illustrated in thefigure 30. The median value for slurry pumpactive power is 255 [kW] for the trace#1 and344 [kW] for the trace#2. The interquartileranges lie between 50±5 [kW] and 380±10 [kW]and 225±5 [kW] and 420±5 [kW] respectively.All registered values lie within capacity rangewith minor episodic exceeding.

The figure 32 demonstrates the comparison ofactive power variations on the MDBs between

0

100

200

300

400

500

600

700

800

Trace#1 Trace#2

Psp [kW

]

Figure 30: Comparison of active power vari-ations on the slurry pump between trace#1and trace#2.

trace#1 and trace#2 and confirms previous ob-servations.

The visual demonstration of time spent on theconstruction of two tunnels is featured in thefigure 33. The two traces have approximatelythe same length.

There is no clear correlation between registeredadvance speed and active power of neither thecutting wheel nor slurry pump in either trace.

0

100

200

300

400

500

Trace#1 Trace#2

Pcw

[kW

]

Figure 31: Comparison of active power vari-ations on the cutting wheel between trace#1and trace#2.

24


Table 4: Averaged degree of mean and max utilisation of the MDB and the main consumers permachine type.

5.4 Comparison of the investigated ma-chine types

5.4.1 Summary of utilisation analysis

The Table 4 provides information about themean and max utilisation of MDBs and respect-ive main consumers averaged for each type ofstudied TBMs. In general the table suggests thatMDB is underused on all types of the machines,cutting wheel is slightly to medium overused(especially on EPBs), screw conveyor of EPBmachines is often overused and slurry pumps ofMixshields are generally loaded to a very goodextent. However the last statement is not ne-cessary correct, since max utilisation of slurrypump is not available for the most of Mixshieldprojects under consideration Appendix X.The figures (Appendix V, Appendix VI) provideinsights into the mean and max utilisation ofMDBs in the studied projects. Mean utilisa-tion for Hardrock machines is between 8% and

0

200

400

600

800

1000

1200

1400

1600

1800

Trace#1 Trace#2

P [kW

]

Figure 32: Comparison of active power vari-ations on the MDB between trace#1 andtrace#2.

22%, for EPBs - between 14% and 65%, for Mix-shields - between 22% and 54%. The highermean values for EPB and Mixshield TBMs canbe explained by the higher amount of main con-sumers in the last two machine types.

The maximum utilisation values of HardrockTBMs lie in range between 55% and 90%, ofEPB TBMs - 38% and 95% and of MixshieldTBMs - 42% and 90%. As one can see max MDButilisation never reaches 100% level. Moreoverseveral machines (B-3, C-6) have maximum loadless then 50% of their total capacity.

Further two figures (Appendix VII,Appendix VIII) demonstrate mean andmax utilisation summary for cutting wheelsof the respective projects. The Appendix VIIsuggests that mean utilisation of the cuttingwheel within Hardrock TBMs varies between5% and 40%. The same range for EPB TBMs is14 to 82% and for Mixshield TBMs - 6 to 45%.

0 500 1000 1500 20007.334

7.336

7.338

7.34

7.342

7.344

7.346x 10

5

Advance ring number [−]

Tim

e [S

erial D

ate

Num

ber]

Trace#1

Trace#2

Figure 33: Correlation between time and ad-vance ring installation within the constructionof trace#1 and trace#2.

25


Table 5: Averaged energy consumption calculated for MDB(s) and cutting wheel per machine type.

Maximum utilisation of the cutting wheel indic-ates rather significant overuse especially in someprojects (Appendix VIII). An extreme case is theproject B-7, where the maximum registered act-ive power exceeds the total capacity of the cut-ter head nearly three times. In many other pro-jects the maximum logged active power is re-markably higher then the nominal capacity ofthe cutting wheel, e.g. in some Hardrock ma-chines (A-1, A-2), EPB machines (B-1, B-2, B-5,B-10, B-13, B-20 and B-21) and Mixshield ma-chines (C-4, C-5, C-8, C-9).The mean and max utilisation rates of screwconveyor were not available for many pre-viously analysed projects. The projects fea-tured with this data are demonstrated on theAppendix IX. As one can see in 3 out of 9 pro-jects the screw conveyor is significantly over-used (up to 250% of its capacity). Out of 9 pro-jects 5 are well balanced and the capacity of thescrew conveyor is used to its full extent. Onlyin 1 project the screw conveyor was used to halfof its capacity.Slurry pump utilisation rates on Mixshield ma-chines with available data are shown on theAppendix X. Out of 9 presented projects 5did not contain values for maximum utilisation.Mean utilisation of all 9 projects is around 50%.The overuse of slurry pump capacity reachessome 150±10% of the full equipment capacity.

5.4.2 Energy consumption

Energy consumption rates averaged for MDBsand cutting wheel from the studied projects permachine type are demonstrated in the Table 5.Taking into the account that the advance ringshave widely different dimensions (diameter,

tubing segment length and thus volume), onlyenergy consumption per unit volume is a uni-fied value to be compared.

According to the Table 5 the average energyconsumption per cubic metre is the highest forMixshield TBMs (18 [kWh]), followed by EPB(15.2 [kWh]) and Hardrock TBM (11.6 [kWh]).When comparing the active power per excava-tion volume an exact opposite situation is wit-nessed. Hardrock TBMs require the most act-ive power (19.9 [kW/m3]), followed by EPBTBMs (17.4 [kW/m3]) and Mixshield TBMs(14.8 [kW/m3]). Thus Hardrock TBMs requirethe most active power in order to break thehardrock, whereas EPB TBMs and even moreMixshield TBMs require less power, but moreoperation time for tunnel construction. EPBTBMs and Hardrock TBMs require the mostenergy for cutting wheel (ca. 9 [kWh/m3]).This value for Mixshield machines is signific-antly smaller (ca. 4 [kWh/m3]). Again themost cutting wheel power needed for tunnel ad-vance is characteristic for Hardrock machines15 [kW/m3] against 10 [kW/m3] (EPBs) and4 [kW/m3] (Mixshields). Thus cutting wheelon EPBs requires less power, but more opera-tion time.

Energy consumption of the machine types un-der consideration per tunnel diameter is shownin the Appendix XI. There are three projects(2 EPBs: B-9, B-13 and 1 Mixshield: C-2.1, C-2.2) showing significantly higher energy con-sumption rates (35, 38, 40 and 41 [kWh/m3] re-spectively). In general the energy consumptionof Hardrock machines varies between 4 and20 [kWh/m3], this of EPBs - 6 to 22 [kWh/m3],and of Mixshields - 4 to 20 [kWh/m3]. There is

26


0 200 400 600 800 1000 1200 1400 1600 1800 20000

2

4

6

8

10

12

14

Advance ring number [−]

Advance tim

e [h]

Trace#1

Trace#2

Figure 34: Advance time plotted against advance ring number for trace#1 (blue line) and trace#2(red line) with in project C-2.

no clear correlation between energy consump-tion per cubic volume and diameter of the tun-nel, which was also validated with a specificscatter plot (not included here).Appendix XII suggests an overview of themean active power per cubic metre, plottedover the diameter of the projects. Activepower of the Hardrock TBMs vary between7 and 33 [kW/m3], of the EBPs between 8and 26 [kW/m3], and of Mixshields - 7 to23 [kW/m3].The following two figures (Appendix XIII,Appendix XIV) provide insights into the samecalculation results, but for the cutting wheel.Energy consumption on the cutting wheelof Hardrock machines varies between 4 and17 [kWh/m3], of EBP - 3 and 21 [kWh/m3],and of Mixshield - 4 to 7 [kWh/m3].Active power on the other hand lies withinrange 4 to 27 [kW/m3] on Hardrock TBMs,4 to 16 [kW/m3] on EBP TBMs and 1 to11 [kW/m3] on Mixshield TBMs.

5.5 Influence of geological conditionsThe figure 34 indicates the relationship betweenconstruction times of the two traces. There is avisible correlation between the two time data-sets, however trace#1 indicates higher time de-mands on section between ring number 200 and1000. The p-value from Ansari-Bradley test is1.8e-88 and from Kruskal-Wallis test - 9.7e-04,

which confirms the significant difference. Thetotal construction time of the trace#1 is 472.6hours longer than that of trace#2, which equalsto almost 20 days. Taking into considera-tion the local geology this probably is a clog-ging problem, which operating crew adapted toand/or machinery was adjusted to.As a result the same machine demonstratesno conformity in either of the selected energyconsumption parameters in similar geologicalenvironments (Appendix XV, Appendix XVI,Appendix XVII).

1 2

0

50

100

150

200

250

300

350

400

Pcw

[kW

]

Figure 35: Comparison of cutting wheel activepower values logged on section A of trace#1and trace#2 (project C-2).

27


1 2 3

0

50

100

150

200

250

300

350P

cw

[kW

]

Figure 36: Comparison of cutting wheel activepower from sections A, B and C (trace#1).

There is a certain conformity between mediansin A section from trace#1 and trace#2, indic-ated by a high p-value resulted from Kruskal-Wallis test (0.1032). The actual median val-ues are 36.7 and 35.8 [kW] respectively. How-ever there is a significant difference between themeans (47.2 and 80.9 [kW] respectively).Figure 35 provides more insights into the vari-ances and medians of the registered values,showing high difference between the compareddatasets.There is no conformity between thelogged slurry pump active power values(Appendix XVII).Further tests conducted include comparison ofcutting wheel active power datasets, collectedin different geological conditions along trace#1and trace#2. Similar tests were conducted withslurry pump active power datasets. None ofthese tests has revealed any significant conform-ity. However when comparing the active powerof the cutting wheel from different geologicalconditions within one trace, as depicted on thefigure 36 the positive correlation between ex-pected increase in hardness of geological condi-tions and increased active power of the cuttingwheel was found.

6 DISCUSSION

6.1 Energy saving potentialThe results of conducted analysis allow identify-ing several measures to reduce the energy con-sumption of the TBM types under considera-tion. The two major measures are optimisation

of energy consumption during operation andadjustment of TBM design to better address thelocal geological conditions. Both of the meas-ures are critical elements of the overall strategyaimed at improvement of EE of the TBMs andshould be implemented in combination.

6.1.1 Effective energy use at operation

Hardrock TBMThe results of the analysis of A-4 project sug-gest that a very large share of logged entries(78%) is within range 0 to 500 [kW]. The me-dian (2157.1 [kW]) and the mean (1727.7 [kW])of the cutting wheel active power confirm thatmost of these values are not associated withthe operation of the cutting wheel and thusmight represent idle running muck transport-ation conveyor, lighting or operation of otherminor consumers. The project implementationprocess included large number of idle periods.This is a sign of insufficient adaptation of themachine or the crew to the local geology. Withthe geotechnical information in hand the pos-sible problems include: convergence, unexpec-ted water inflows, hazardous gases, rock fall etc.

The analysis of A-6 project shows similar res-ults. Large share of registered values (59%) re-mains in the range between 50 and 1000 [kW].At the same time median and mean of act-ive power of the cutting wheel are 2363.4 and2128.4 [kW] respectively. Thus less then in caseof A-4 but yet large amount of logged entries arenot associated with the cutting wheel operation.As demonstrated in Results energy consump-tion during the numerous idle periods contin-ues on MDB1. Thus minor consumers connec-ted to this power supply unit should be inspec-ted and analysed more in detail. No reasonablearguments for idle periods could be found ingeotechnical report, except of high wear ratesin some sections.

EPB TBMBoth B-14 and B-15 machines (similar design,same geology) indicate high share of activepower data within the range 0 to 200 [kW](82.6%). There are major stops during whichenergy consumption continues to take place inboth projects, which is an indicator for possiblyserious operational problems. The geology is inthe area of concern is highly diverse with chan-ging groundwater conditions, abrasivity and co-

28


hesiveness of the soils, which could cause waterinflow, clogging and wear of the machinery.

A similar situation is faced in B-16 project,where 68.1% of the registered active power val-ues lie within range 0 to 200 [kW], and 13.9% -within range 75 to 100 [kW]. The median of thecutting wheel active power is 130±10 and thisof screw conveyor is 40±5 [kW]. Thus the ma-jority of the registered active power values rep-resent the cutting wheel and screw conveyor op-eration. There is one major idle period, wherethe energy consumption data is missing. Be-fore the idle period the screw conveyor showsconstant overloads, which probably caused themajor damage and required repair. No energyconsumption is registered during the reparationperiod. The geotechnical report lacks crucialinformation on abrasivity and rock quality, butsecondary wearing of the screw conveyor is re-ported. Apart from the overloaded and presum-ably broken screw conveyor, the project can beassessed as energy efficient due to low energylosses.

In B-17 and B-18 the large share of registeredvalues (59.5% and 67.3% respectively) is withinrange 0 to 400 [kW]. Since the capacity of thescrew conveyor is 315 [kW], a portion of thesevalues represents its operation. There are manystops during the project, with the major onefrom 20-07-2012 to 30-07-2012. Generally onlyduring the major idle period the energy con-sumption is taking place, which indicates crew’sattempt to reduce energy consumption. Pos-sible reasons for the stops include water inflows(permeability of the rock is not investigated,karst and cavities are expected) and hazardousgases occurrence (methane, hydrogen sulphide,oxygen, carbon dioxide and carbon monoxide).

B-20 and B-21 is another example of two ma-chines with the same design operating in similargeological conditions. Both machines demon-strate skewness in load allocation not character-istic for other analysed projects, where MDB1has higher loads. Apart from supplying thehalf of the cutting wheel drives (the other halfis connected to MDB2), MDB1 probably al-locates part of its capacity for screw conveyorand other rather minor consumers. The ac-quired histograms support this hypothesis. Themost frequent range for MDB1 on B-20 is 0 to250 [kW] (73.5%), for MDB2 - 0 to 175 [kW]

(71%). Medians are 130.7 and 32.8 [kW] re-spectively. B-21 shows very similar observa-tions. The higher median on MDB1 is a resultof screw conveyor supply (maximum capacity400 [kW]). Further inspection of the data allowsconfirming energy consumption during stops.Mixshield TBMThe only Mixshield project with available es-sential data is C-2. In this project the sameMixshield TBM has driven two parallel tracesof the same length. It is remarkable that thefirst trace has more idle periods with generallylonger duration. In total the construction ofthe first trace required additional 472.6 hoursor almost 20 days. The share of the values inthe range 25 to 200 [kW] are relatively sim-ilar for both traces and represent some 22%.Trace#1 has a longer set of values, and smal-ler median active power (32 [kW]) when com-pared to trace#2 (92.6 [kW]). Thus tunnel ad-vance process was longer but with smaller act-ive power per unit time during the advance ofthe trace#1. The higher values are also charac-teristic for the slurry pump.

The longer time, required for the constructionof the trace#1 might indicate adaptation of themachine and crew operation to better addresspeculiarities of local geology. This points outthe necessity and positive influence of geotech-nical data availability for tunnel constructionprojects also discussed in (B. Maidl L. S., 2008).At the same time the energy consumption res-ults described in the following section indicateslightly higher energy consumption during theconstruction of trace#2. This might mean thatfaster construction requires higher energy con-sumption. However there is another possiblereason for this. During the calculation of en-ergy consumption idle times were excluded, asdescribed in the methodology section. Thusthis methodology could be the reason for thelowered energy consumption during the con-struction of the trace#1.

To conclude, based on the analysis of the invest-igated TBMs the main energy saving potentialis in the better adjustment of the machinery tothe local geology (requiring sound geophysicalinvestigation prior to development of machinedesign) and as a result minimisation of idle peri-ods during the construction, implementation ofeither automatic or manned deactivation of idle

29


running tools as well as overall improvement ofproject management with the focus on EE.

6.1.2 EE by designHardrock TBMIn A-4 the maximum load including minor out-liers is approximately 1250 [kW], whereas thefull capacity of the MDB1 is 2200 [kVA] (or1980 [kW]). MDB2 and MDB3 are used to theirfull capacity, maximum load of 2400±50 kW,full capacity is 2800 [kVA] or 2520 [kW]. Asa result at least 25% of the total capacity re-mains idle during the entire project. The cut-ting wheel drives capacity is very well balancedand the entire installed power is used.The MDB1 installed on A-6 indicates the loadsof up too 1000±50, whereas the full capacityis 2250 [kW]. MDB2 and MDB3 are also usedto almost their full capacity (3000±25 from3240 [kW]) and as a result at least 25% of thetotal capacity remains idle. The cutting wheeldrives capacity is very well balanced. Thus theresults of the analysis of both Hardrock TBMsallow the same observations.The results of utilisation analysis of all stud-ied machines reveal that mean MDB utilisa-tion for Hardrock machines is between 8 and22%, whereas maximum utilisation is in rangebetween 55 and 90%. It is important to mentionthat only total MDB capacity is considered herewith no distinction of installed MDBs contrib-uting to the total capacity. Mean utilisation ofthe cutting wheel within Hardrock TBMs variesbetween 5 and 40%, whereas the maximum util-isation in many projects is remarkably higherthen the nominal capacity of the cutting wheel.The examples of such Hardrock machines areA-1 and A-2 with max cutting wheel utilisationof 180 and 150% respectively.EBP TBMsMost of the EPB machines investigated in detailshow very good MDB total active power util-isation patterns. Both sister machines B-14 andB-15 show a balanced utilisation pattern withmaximum utilised capacity of 1600±25 out of1800 [kW] (12% reserve), B-16 1200±50 out of1350 [kW] (9% reserve), B-20 and B-21 1600±50out of 1800 [kW] (16% reserve). The resultsof the analysis of B-17 and B-18 projects sug-gest overpowered MDBs. Only 1500 out of2700 [kW] is utilised (42% reserve). B-16 indic-ates another flaw of constant overload of screw

conveyor, presumably leading to a long-termstop, as discussed previously. Moreover screwconveyor is overloaded on B-14, B-15 and B-16.Overload of the cutting wheel takes place ononly B-20 and B-21, whereas in other projectsthe cutting wheel demonstrates rather remain-ing reserve (10 to 20%).

The comparison of utilisation patterns amongall studied machines confirms the previousstatement. Mean utilisation of the MDB isbetween 14 and 65%, whereas max utilisationvaries between 38 and 95%. Mean utilisation ofthe cutting wheel power is in range 14 to 82%,whereas maximum utilisation often exceeds themaximum capacity (B-1, B-2, B-5, B-10, B-13,B-20 and B-21). Moreover the overload of thescrew conveyor takes place in several of the in-vestigated projects.

Mixshield TBMsThe utilisation analysis of the C-1 Mixshieldproject confirms already stated hypothesis thatthe same machines or machines with similardesign show similar utilisation patterns in thesame geological conditions. Both traces boredthroughout C-1 indicate well-balanced MDButilisation (3 and 14% reserve on trace#1 andtrace#2 respectively) as well as slight overloadof cutting wheel (-21 and -7% reserve) and screwconveyor (-11 and -14% reserve). Despite higheroverall advance rate and generally higher activepower values on both MDB and cutting wheelfor trace#2 as presented in Results section, thepick values are higher for the trace #1, whichmight indicate wear or reported clogging prob-lem.

The comparison with all other investigated pro-jects suggests that mean MDB utilisation ofMixshield TBMs is between 22 and 54%, maxMDB utilisation - 42 and 90%. Mean cuttingwheel utilisation ranges from 5 to 40%, and maxutilisation often exceeds the capacity.

The overloads of the machinery lead to break-age and as a result cause expensive and energyconsuming idle periods, discussed in the previ-ous section of this report. Thus in order to im-prove the EE the optimisation of the machinesdesign is required. This will allow the adjustingof energy suppliers and excavation tools to bet-ter address the local geological conditions andas a result minimise expensive idle periods.

30


6.2 Geology dependenceThe results of the geology dependence studyinvolved two Mixshield projects with two par-allel traces of the same length. Generally thestudy did not confirm significant conformitybetween the torques and energy consumptionlogs from the MDBs, cutting wheel and slurrypump logged on the same machines during tun-nel construction in similar geologies. In C-1there is a certain degree of conformity in vari-ances, whereas there is no or very little con-formity in medians. In C-2, on the other hand,no conformity is witnessed.There are several main reasons explaining lowlevel or absence of conformity within these pro-jects:

1. Highly heterogeneous and anisotropicconditions in the geological environmentsencountered in both projects. Themain geological formations include glacialtill with various inclusions (coarse sand,gravel, fine sand etc.), ground morainewith various inclusions (glacial loams, till,gravel etc.). The conditions in such form-ations are very directionally dependant,which affects the energy consumption.

2. Level of adaptation of the operating crewbased on the availability of detailed in-formation about the confronted geologicalconditions and the ability to cope with thechallenges and risks of the local geology(clogging, water inflows, hazardous gasesetc.). This variable exerts influence on theintensity and EE of the construction pro-ject.

3. Level of adjustment of the machinery.During the construction of the tunnelchanges are often being made to theTBM in order to improve its perform-ance, change of the cutting wheel elements,transportation tools etc. Such improve-ments are meant to better address the localconditions and might significantly affectthe EE.

4. In geological conditions with certainamount of abrasive materials the excava-tion and transportation tools are exertedto stresses, which cause primary and sec-ondary wearing of the excavation tools and

thus gradually, but constantly deterioratethe TBMs’ performance. This also affectsthe energy consumption patterns as well asEE in general.

5. Time constraints. Every project has estim-ated implementation time and in case ofdelays local authorities or other costumersmight exert pressure on the personnel inorder to intensify the construction processand meet the deadline, which also has aneffect on energy consumption and EE.

At the same time there is evidence found thatsupport the hypothesis of influence of geo-logy on energy consumption along the sametrace. This however requires further invest-igation, since it is not characteristic for allstudied cases. Moreover attention should bepaid to which datasets are considered importantand significant for geology dependence analysis,as discussed in previous study (Heim, 2007).Moreover according to this research a direct at-tribution of the logged datasets to the geotech-nical parameters is desirable, but not possibledue to lack of high-definition data. The report(Heim, 2007) suggests that apart from torque,clamping force should be taken into consid-eration, since during the increasing clampingforce/contact force there is an increase in torqueand volume of the excavated muck. Thus formore detailed and precise results all relevantparameters (e.g. torque, clamping force andamount of excavated materials, calculated fromlogs of slurry pump) should be taken into con-sideration. Several sensors should demonstraterelevant correlations at the same tunnel metrein order to allow identification of geological in-fluence (Heim, 2007). A comprehensive ana-lysis of this kind is beyond the scope of thisproject. However for further endeavours in thisarea these recommendations should be takeninto consideration.

6.3 LimitationsThe given research has a number of limitations.When comparing the EE of various machinetypes it is normally not possible to acquire thedata of application of different machines in thesame or even similar geological environments.This however is a very important factor, whichaffects the TBM operation, its advance rates andthus EE of a TBM dramatically. In this research

31


project an attempt is made to whenever possibleconsider the peculiarities of different geologicalenvironments and their implications on the op-erational efficiency of the TBMs under consid-eration.Most of the data used in the research repres-ent pre-processed and calculated values, includ-ing geotechnical descriptions, torque and activepower of the MDBs as well as active power val-ues of the main energy consumers. In this re-search the attempt is made to eliminate any mis-takes in the processed data through the extens-ive data quality and integrity assessment. Thedata however still remains a close approxima-tion and should be treated as such.The location of the TBM in space is measuredin 1D based on front/rear reference point oris calculated based on the support rings num-ber (advance ring number) and its’ length. Ittherefore does not account for the differencesin effects of radial forces in hardrock and in softmaterials, which can have strong influence espe-cially in traces with a tight radius (Gesellschaftfür Vermessungstechnik, 2005).

6.3.1 Safety issuesSome potential energy saving measures mightlead to a reduction of safety level during theoperation of a TBM. This should be investig-ated more in detail, paying special attention tominor energy consumers, which were out of thescope of this report.Such potential safety issues can be associatedwith e.g.:

• Lighting of the TBM area. The energyfor tunnel maintenance such as ventila-tion, lightning of the tunnel, power supplyof auxiliary machines and tools, includingwhere applicable railway muck transport-ers and traffic lights is secured by MDBs in-stalled outside of the TBM, usually on thesurface at the start point. However lightsilluminating the TBM area are poweredfrom internal MDB. In such cases EE prac-tices can only include replacement of en-ergy demanding equipment with more en-ergy efficient analogues (LED lamps), butnot full deactivation of the consumer dur-ing periods of manned operation.

• Analysis conducted by Benedikt Brodarevealed idle running slurry pumps on

some Mixshield projects. The deactiva-tion of the pumps during long-term stopsis desirable. However continuous deac-tivation/reactivation of some energy con-sumers may lead to accelerate performancedeterioration and should be avoided. Aninvestigation aiming at definition of long-and short-term stops as well as deactiva-tion/reactivation mechanisms for such idlyrunning consumers is required.

6.3.2 Productivity losses and consumerawareness

Due to the high costs of TBMs and rather lowshare of energy costs in the overall constructionproject expanses, the consumers are in generalinterested in high penetration (the advance perrotation rate) and advance rates (Maidl et al.,2008) and thus might not be willing to reducethe installed power. This is one of the mainlimitations for the implementation of the greenTBM concept.

6.3.3 On-site operation techniques

Another implication of relatively low energycosts is the on-site operation techniques used bythe TBM crew, which may not give high prior-ity to energy saving measures during the opera-tion. This is however one of the most import-ant stages for an effective energy usage duringan application of TBM.

6.4 EE implementation strategyTo tackle the challenges of EE implementationas well as both of the problems described in6.3.2 and 6.3.3 an EE implementation strategyoffer, including the recommendations from(McLean-Conner, 2009) shortly presented inthe literature review, is developed and describedbelow. It is based on three main arches: dataacquisition and analysis, capacity building, andmarketing (Fig. 37 and Fig. 38).

I. Data acquisition and analysisThe problem of data availability and the qual-ity of the acquired data as well as the necessityof the high quality data has been discussed by(Heim, 2007). The author of this paper pointsout the problem of often faulty, not plausible ormissing data, which requires manual data ana-lysis, significant time investments and thus, in-creases the costs of data analysis. As highlighted

32


Regular updates

via internet etc.

Energy

consumption

data

Geotechnical

data

Data sharing

agreement

HK Data Analysis

Centre

Costumer HK AG

ISISDetailed reports

from

construction

site

I. Data acquisition and analysis

Geological

conditions

profiles

Hardrock

TBM

EBP TBM

Mixshield

TBM

Design

features

Design

features

Design

features

Quality control

Automated

analysis

algorithms

Tailoring to geographic locations

Energy

consumption and

utilisation patterns

II. Capacity building

Project energy

efficiency

assessment

Results of data

analysisLessons

learnt

Energy Efficiency training for the

managerial staff and TBM crews on

such topics as decision-making on TBM

type, energy efficient TBM design,

energy efficient operation practices.

Figure 37: EE implementation strategy (part I and II).

by the author there is an urgent necessity ofquality management for the data stream. It canbe added that it also significantly decreases theefficiency of data analysis in general allowingto only use a minor portion of the potentiallyavailable data. At the same time there is a needto evaluate a larger number of TBMs and theirdata in order to reach a statistically significantamount (Heim, 2007).

Moreover taking into consideration the influ-ence of geological conditions on the energy con-sumption and the necessity to study this cor-relation more in detail, special attention shouldbe paid to the collection of high-resolution geo-technical data. The detailed geology descrip-tion can be acquired from the ISIS geophysicalinvestigation system patented by HerrenknechtAG as well as from reports prepared during thetunnel construction on site.

According to the offer both data logs ac-quired from the TBM sensors and geotechnicaldata should be delivered to HK Data AnalysisCentre. To enable legal protection, data shar-ing agreement to be signed by both client andthe producer needs to be introduced, as an op-tional binding supported by HK incentives (asdiscussed further). The acquired data will be

regularly transmitted to the HK Data AnalysisCentre via encrypted communication channels.HK Data Analysis Centre conducts a continu-ous preliminary quality control as well as EEanalysis similar to that conducted in the frame-work of this research. In order to increasethe performance, automated data analysis al-gorithms are developed and deployed to pro-duce on-going and final EE reports for eachmonitored project. The correlations betweenthe energy consumption logs and local geolo-gical conditions are constantly investigated. Asa result there is a growing database of geolo-gical profiles linked to geographic locations fea-tured with the respective energy consumptionand utilization patterns, which allows facilitat-ing the decision-making process on selection ofTBM type and further design features, all basedon the best practices from the past.II. Capacity buildingOne of the consequences of the on-going ana-lysis described above is the constant evaluationof EE of the projects. This assessment will allowidentifying strengths and weaknesses of each in-dividual project. The information is than com-municated by Herrenknecht representatives tothe project management as well as to TBM op-erating crew in form of short-term trainings.

33


III. Marketing

EE implementation value added for the developed economies worldwide

Wide public awareness

campaign, including

popular science films,

broadcasted on TV and

via Internet to create

bottom-up lobby and to

facilitate the costumers'

choice

Use information and

significant examples to

convince consumers

and motivate them

purchase

environmentally friendly

TBMs from HK

Quantification of

energy savings

over a period of

time

Demonstration of

the savings in

easy-to-grasp

numbers

(average-size

towns supplied

with energy,

tones of coal

saved etc.)

Secure proper

labeling and

visibility

guidelines by

involving of EE

lobbying

organisations

Elaboration of

educational

materials (video,

printed etc.) with

concise and

comprehensible

descriptions of

the EE

technologies

Figure 38: EE implementation strategy (part III).

These complementary trainings should repres-ent incentive for the client to join the EE mon-itoring program, by signing the data sharingagreement.

Furthermore short-term educational activitiescan be implemented in order to address the issueof insufficient TBM type selection by the client,as was stated previously. This can be one-dayseminars for the top-managers and further train-ings for the workers on site, which are conduc-ted prior to the project commencement. Thegoal is to select the best-suited TBM type andto train the crew for operation in the expectedgeological conditions.

III. MarketingEE and environmental friendliness of theproducts and services in general create value ad-ded, which allows raising competitive capacityand facilitate decision-making, especially in de-veloped societies with high value of environ-mental awareness. Environmental Impact As-sessment (EIA) is a formal process of positiveand negative environmental impacts estimationof a development project, wide spread in societ-ies with environmental concerns. Public parti-cipation being one of the main procedures ofEIA determines the key marketing elements:

preparation of educational materials and secur-ing the proper labelling, as well as broad dissem-ination of the information and lobbying on thepolitical level. The organisations advocating EEdescribed in the literature review can be contac-ted for further information and support.

7 CONCLUSIONS

The findings of this study confirm the existenceof data quality issue and highlight the necessityof data quality control. Quality data is essentialfor further research on EE due to the complex-ity of the tunnel advance process caused by widevariety of machine types, dependence on oftenhighly heterogeneous geological conditions andother project specifications (diameter of the tun-nel, operating mode etc.). In order to reachmeaningful results with proper statistical signi-ficance more projects need to be analysed, in-volving relevant logs from TBMs discussed inthis paper as well as high-resolution geotech-nical data.The outcomes of the analysis allowed identi-fication of specific distinctions between energyconsumption of the three investigated TBMtypes. According to the gained results, av-erage energy consumption per cubic metre is

34

the highest for Mixshield TBMs, followed byEPB and Hardrock TBM. At the same time thecomparison of the active power per excavationvolume indicates the exact opposite situation.Hardrock TBMs require the most active powerand Mixshield TBMs the least. Thus HardrockTBMs require the most active power in orderto break the hardrock, whereas EPB TBMs andeven more Mixshield TBMs require less power,but more operation time for tunnel construc-tion. Similar situation is observed for the en-ergy consumption of the cutting wheel on thethree machine types. Moreover the results ofenergy consumption study show that there isno direct correlation between the diameter ofthe tunnel and energy consumption per excav-ated cubic metre neither within the same TBMtype or between the three compared groups.

Utilisation analysis suggests the necessity foroptimisation of the layout of MDBs and ma-jor consumers of TBMs for all types of stud-ied machines. Low capacity MDBs supplyingmainly minor consumers are often overpoweredas was demonstrated in analysis of HardrockTBMs. MDBs with higher capacities supply-ing cutting wheel drives and other major con-sumers are generally well balanced. Cuttingwheel drives and screw conveyors are oftenoverloaded, which in some extreme cases mightlead to long-term stops. Moreover the study re-vealed that sister machines in similar geologicalenvironments show similar utilisation patternsof MDBs and main consumers. The over- aswell as underused units are identified, presen-ted and discussed. Further research should be-side the total MDB capacity utilisation, also in-clude utilisation analysis of each installed MDB.This will supplement the gained information.Moreover max utilisation of screw conveyorand slurry pump are of interest and should beincluded into analysis.

Considering the geological influence on energyconsumption, generally the study did not con-firm significant conformity between the en-ergy consumption of the same machines boringthrough sections with similar geological envir-onments. There are several reasons, explainingthis phenomenon, including highly heterogen-eous and anisotropic geological conditions inboth studied projects, level of adaptation of thecrew and adjustment of the machinery as well

as time stress. At the same time some evid-ence of expected geology dependence were dis-covered when analysing data logged within thesame tunnel trace. In general dependence of en-ergy consumption on the geological conditionsrequires further research.The results of this survey suggest that there is acertain energy saving potential, which is achiev-able by an adequate selection of the machinetype prior to start of a given project and betteradjustment of the machines’ layout to the par-ticular local geological environments. Last butnot least some energy saving potential is achiev-able through optimisation of tunnel boring op-eration on site. However this is strongly projectspecific and requires further continuous inspec-tion covering inter alia energy consumption bythe minor consumers. Moreover an investig-ation aiming at definition of long- and short-term stops as well as deactivation/reactivationmechanisms for idly running consumers is re-quired.An EE implementation strategy is suggestedand discussed. Each of its steps is a complex pro-cess, implying wide range of activities. The ac-cess to customers’ energy consumption data andgeotechnical data is a corner stone for the devel-opment and secure implementation of EE solu-tions. The development of automated tools forEE analysis will significantly improve its per-formance and decrease costs. The on-going ana-lysis of EE should preferably provide quantit-ative estimation of energy saving potential perproject, allowing making a stronger point forfollow-up meetings and trainings.

35


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Appendix IOverview of geotechnical properties along the trace of A-4

Ground / rock types (clay / rockminerals)

Share trace: UCS [MPa] k-value[m/s]

a) Limy Schists, alternating contentsof marble and phyllites

99% 50-150 1 x 10−10 −10−12

b) Massive anhydrite 1% 40-60 1 x 10−10 −10−12

Appendix IIOverview of geotechnical properties along the trace of B-16

Ground / rock types (clay / rock minerals) Share trace: k-value[m/s]

a) Clay and silty clay 62% 1.3 * 10−7 −6 ∗ 10−7

b) Mixed fine-grained sandstone / silty clay 6.2% N/Ac) Clay, silty clay, clayey and silty sand 31.8% 3.2 *10−4 −

1.5 ∗ 10−8

Appendix IIIOverview of geotechnical properties along the trace of C-2

Ground / rock types (clay / rock minerals) Share trace: Cu[KN/m2]

a) Quaternary: organic soft layers (alluvial mud, clay soil,peat, organic silt)

1% 5-30

b) Quaternary: ground moraine (glacial loams, till withinclusions of gravel, sand, silt, clay as well as rocks, e.g.erratic blocks and boulders)

20% 50-150

c) Quaternary: sands, with inclusions of gravel and localboulder enclaves

14% 20-130

d) Tertiary: mica silt, mica clay, local mica sand enclaves 65% > 200

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Appendix IVMain geological sections per ring/meter C-2 (similar conditions are marked with colours)

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Appendix VMDB mean utilisation summary

Appendix VIMDB max utilisation summary

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Appendix VIICutting wheel mean utilisation summary

Appendix VIIICutting wheel max utilisation summary

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Appendix IXScrew conveyor mean and max utilisation summary

Appendix XSlurry pump mean and max utilisation summary

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Appendix XITotal energy consumption per excavation volume [m3]

Appendix XIIMDB active power per excavation volume [m3]

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Appendix XIIICutting wheel energy consumption per excavation volume [m3]

Appendix XIVCutting wheel active power per excavation volume [m3]

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Appendix XVStatistical test results for comparison MDB active power between trace#1 and trace#2 (project C-2)

Appendix XVIStatistical test results for comparison active power of the cutting wheel between trace#1 and trace#2(project C-2)

Appendix XVIIStatistical test results for comparison active power of the slurry pump between trace#1 and trace#2(project C-2)

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Documents

ENERGY EFFICIENCY OF TUNNEL BORING MACHINES