Ändra sökning
Avgränsa sökresultatet
1234567 101 - 150 av 2313
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf
Träffar per sida
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sortering
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
  • Standard (Relevans)
  • Författare A-Ö
  • Författare Ö-A
  • Titel A-Ö
  • Titel Ö-A
  • Publikationstyp A-Ö
  • Publikationstyp Ö-A
  • Äldst först
  • Nyast först
  • Skapad (Äldst först)
  • Skapad (Nyast först)
  • Senast uppdaterad (Äldst först)
  • Senast uppdaterad (Nyast först)
  • Disputationsdatum (tidigaste först)
  • Disputationsdatum (senaste först)
Markera
Maxantalet träffar du kan exportera från sökgränssnittet är 250. Vid större uttag använd dig av utsökningar.
  • 101.
    Almgren, Torgny
    Luleå tekniska universitet.
    Time planning under uncertainty in a mining environment1989Licentiatavhandling, monografi (Övrigt vetenskapligt)
  • 102.
    Alsyouf, Imad
    et al.
    Industrial Engineering and Engineering Management, University of Sharjah, Sharjah, United Arab Emirates.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Al-Ash, Lubna
    Industrial Engineering and Engineering Management, University of Sharjah, Sharjah, United Arab Emirates.
    Al-Hammadi, Muna
    Industrial Engineering and Engineering Management, University of Sharjah, Sharjah, United Arab Emirates.
    Improving baggage flow in the baggage handling system at a UAE-based airline using lean Six Sigma tools2019Ingår i: Quality Engineering, ISSN 0898-2112, E-ISSN 1532-4222, Vol. 30, nr 3, s. 432-452Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper presents a real successful implementation of lean six sigma methodology to continuously improve the baggage flow in a baggage handling system (BHS), by identifying the causes of mishandled baggage, and deriving solutions to enhance BHS performance. The results show that the main critical problems were low system reliability and the high number of bags passing through manual-encoding-stations. This research illustrates how to avoid baggage congestion and provides applicable and cost-effective solutions. The success of this project made the organisation aware of the opportunities that the application of lean Six Sigma methodology created in the aviation and airport sector.

  • 103. Amadei, Bernard
    et al.
    Stephansson, Ove
    Luleå tekniska universitet.
    Rock stress and its measurements1997 (uppl. 1)Bok (Övrigt vetenskapligt)
  • 104.
    An, Bolun
    et al.
    School of Civil Engineering, Beijing Jiaotong University, Beijing, China. Beijing Key Laboratory of Track Engineering, Beijing, China. Beijing Engineering Research Centre of Rail Traffic Line Safety and Disaster, Beijing, China.
    Gao, Liang
    School of Civil Engineering, Beijing Jiaotong University, Beijing, China. Beijing Key Laboratory of Track Engineering, Beijing , China. Beijing Engineering Research Centre of Rail Traffic Line Safety and Disaster, Beijing, China.
    Xin, Tao
    School of Civil Engineering, Beijing Jiaotong University, Beijing, China. Beijing Key Laboratory of Track Engineering, Beijing, China. Beijing Engineering Research Centre of Rail Traffic Line Safety and Disaster, Beijing, China.
    Lin, Jing
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    An approach to evaluate wheel-rail match properties considering the flexibility of ballastless track: Comparison of rigid and flexible track models in wheel-rail profile matching2019Ingår i: International Journal of COMADEM, ISSN 1363-7681, Vol. 22, nr 3, s. 5-13Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Many different wheel/rail profiles are used in the China high-speed railway, and vehicle operation safety and comfort will decrease if the inappropriate wheel-rail profile pair is used. To solve the problem of estimating the wheel-rail match, many numerical models, including vehicle system dynamic models and wheel-rail rolling contact models, have been established to analyse the wheel-rail dynamic responses. Both methods have less consideration of the flexibility and vibration characteristics of ballastless track, leading to deviations in the calculation of middle and high frequency vibration. This paper proposes a vehicle-flexible track coupling model and compares it with the vehicle dynamic model (vehicle-rigid track model). In the rigid track model, only the track irregularities are considered in the track module; the vibrations and deformations of rails, track slab and the foundation are considered in the flexible track model. Taking Chinese CRH3 series wheel profile S1002CN and rail profile CHN60 as examples and considering different track excitations, the two models are compared. The wheel-rail interaction forces, wheel-rail wear depths, wear volumes and vehicle accelerations are chosen as analysis indices for the comparative study.

    The results show that the wheel-rail forces of the flexible track model are larger than the rigid track model in the frequency range from 70 to 120Hz, while they decrease obviously in the frequency range above 150Hz. The differences in wear depths and volumes between the two models exceed 10%. Therefore, the flexible track model should be considered when studying the match properties of different wheel-rail pairs.

  • 105.
    Anand, Adarsh
    et al.
    Department of Operational Research, University of Delhi.
    Agarwal, Mohini
    University of Delhi.
    Bansal, Gunjan
    Department of Operational Research, University of Delhi.
    Garmabaki, Amir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Studying product diffusion based on market coverage2016Ingår i: Journal of Marketing Analytics, ISSN 2050-3326, Vol. 4, nr 4, s. 135-146, artikel-id 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Market coverage is an important attribute for determining the success of a product. The larger the market covered by a product is, the higher the amount of sales for that product will be. Market coverage strategies thus contribute to the success of a product in tapping the market. In this study, we emphasize the impact of market coverage on the rate of adoption in determining product sales. New product diffusion models based on the market covered are proposed. A methodological approach of weighted criteria is implemented to evaluate and rank the proposed models. The analysis is conducted on real-life sales datasets

  • 106.
    Anandika, Rayendra
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Stenström, Christer
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Non-destructive measurement of artificial near-surface cracks for railhead inspection2019Ingår i: Insight (Northampton), ISSN 1354-2575, E-ISSN 1754-4904, Vol. 61, nr 7, s. 373-379Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper delivers a study involving the inspection of artificial surface cracks with depths ranging from 0.25-2.5 mm from the surface and with a crack angle of 30°, which is a typical angle for surface cracks in railheads. The inspections were conducted using three different techniques: phased array ultrasonics, single-element ultrasonics and alternating current potential drop (ACPD). For the ultrasonic techniques, the study focused on employing either longitudinal or shear wave signals. In the railway industry, shallow surface cracks in railheads are caused by rolling contact fatigue (RCF). In this study, artificial defects were made, allowing the authors to explore the extent to which the ultrasonic measurement techniques can detect such defects. The negative effect of a dead zone near to the surface in the ultrasonic tests was reduced by using a wedge attachment. A discussion on the extent to which the techniques can be used in field tests was also provided. The most important result is that shallow cracks ranging from 0.25-2.5 mm were successfully characterised with acceptable accuracy. The 2.5 mm-deep crack can be measured with an accuracy of 0.8% using a 20 MHz single-element probe and with an accuracy of 3.5% using a 5 MHz phased array (64 elements, 0.6 mm pitch). The characterisations were performed using a filtering method that was developed in this study.

    1675605

  • 107.
    Anderson, Anne Lee
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Assessment of thermal radiation arithmetic's for jet flames: A study involving generic calculation methods concerning radiation from jet flames with the purpose to determine the safety distance for flame effects2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Jet flames are commonly used as flame effects in pyrotechnical shows, and are also a possible risk in industries that uses pressurised flammable gas. For these users it is important to  make fire safety engineering calculations to minimise the risks. This project focus on jet flames that are used in pyrotechnic shows where, e.g. it is important to determine the safety distance to the audience. Up to now most studies made concerning jet flames regards jet flames in subsonic regiments, whilst there is a lack of studies concerning sonic jet flames and mathematical formulations for radiation from these cases are limited. This makes pre-determination of temperatures, safety distances, flame heights etc. a challenge. Based on information found, and assumptions when needed, calculations of the safety distance were made. 

  • 108.
    Andersson, G.
    Luleå tekniska universitet.
    Creep experiments on powder1983Ingår i: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 12, nr 6, s. 312-314Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The change in strain during constant loading in die, isostatic and triaxial compaction has been studied for tungsten carbide powder. The creep effect change is largest for isostatic loose powder compaction whereas the slightly precompacted specimens (20 MPa) show less strain change. The creep effect gives modest contributions to the total strain for reasonable times. The highest pressure at which the effect has been recorded is 200 MPa

  • 109.
    Andersson, Joel
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Hagberg, Ludvig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Stability Analysis of High Concrete Dams: Longtan Dam - a case study2018Självständigt arbete på avancerad nivå (yrkesexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
  • 110.
    Andersson, Lena
    Luleå tekniska universitet.
    Resource constrained mine project scheduling using critical path method1992Doktorsavhandling, monografi (Övrigt vetenskapligt)
  • 111.
    Andrén, Anna
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Degradation of rock and shotcrete due to ice pressure and frost shattering2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Nedbrytning av berg och sprutbetong på grund av istryck och frostsprängningPå senare år har Banverket märkt en ökning av inrapporterade nedfall av berg och sprutbetong i sina järnvägstunnlar. I och med detta så startades en rad forskningsprojekt kring problemen med vattenläckage och isbildning i tunnlar. Detta projekt "Nedbrytning av berg och sprutbetong på grund av istryck och frostsprängning" är ett av dessa. Syftet med detta licentiatprojekt var att samla erfarenhet och information om hur is bildas samt hur istryck påverkar krosszoner, sprickor och framför allt skiktet mellan berg och sprutbetong. Vidare testas hypotesen från litteraturstudien och resultaten från laborationsförsök redovisas.När vatten fryser till is sker en 9 % volymsutvidgning och denna expansion kan orsaka att ett tryck uppstår mot det omgivande materialet. Det omgivande materialet kommer att utsättas för brott om trycket från isen överstiger materialets draghållfasthet eller vidhäftningshållfasthet i skiktet mellan berg och sprutbetong. Storleken på skadan är bland annat beroende av materialets vattenmättnad. Ett delvis vattenmättat material kan klara sig från brott, trots att dess draghållfasthet är låg, genom att expansionen av isen och omfördelning av porvatten kan ske i de porer som från början var fyllda med luft. Ett helt vattenmättat material ger istället efter för frostsprängningen oberoende av sin draghållfasthet, på grund av att materialet inte har något fritt utrymme som kan ta upp expansionen.Det är inte bara isens volymsutvidgningen som orsakar frostsprängning. Forskning visar att om berg har tillgång till fritt vatten under nedkylningen sker en process som liknar den i jord, där vatten vandrar fram mot frysfronten och bildar islinser. På ett liknande sätt vandrar vatten i berg och orsakar tillväxt av isskikt i exempelvis en por eller spricka, vilket kan orsaka att istrycket ökar. Vattenvandringen sker på grund av att det finns en tunn vattenfilm av adsorberat vatten längs mineralkornens ytor och i denna vattenfilm finns möjlighet för vatten att vandra mot frysfronten. Experimentellt arbete har visat att en betydande del av det adsorberade vattnet förblir ofruset vid negativa temperaturer, inte bara i jord utan även i berg och detta möjliggör vattenvandringen.Vattenvandring och istillväxt är inte bara beroende av tillgången till vatten och frystemperatur, utan även av fryshastighet och varaktighet av köldgrader. Om berg och sprutbetong utsätts för snabb nedkylning minskar vattenfilmens tjocklek och vattenvandringen förhindras, vilket begränsar frostsprängningen av materialet. Om istället berget kyls ned långsamt, tillåts vattenvandringen att ske under en längre period, vilket kan resultera i större frostsprängning. I de utförda fältundersökningarna visade det sig att varaktigheten och förändring av frysperioderna var av stor vikt för tillväxten av isformationer. Om frysperioden hade lång varaktighet frös vissa av sprickorna och läckagepunkterna. Om läckagen istället utsattes för kortare perioder av frysning och tining frös aldrig sprickorna och vatten fortsatte att läcka med växande isformationer som följd. För kalla områden, som i de norra delarna av Sverige, uppstår dessa problem även långt in i tunnlarna. Problemen uppstår på grund av att läckagevatten transporterar fram värme från bergmassan till den kalla tunnelytan. Värmen från läckagevattnet håller bergmassan kring spricköppningen ofrusen trots att tunnelluften är kall. Därför fortsätter sprickan att föra fram vatten med konsekvensen att det bildas is när vattnet väl kommer ut i den kalla tunnelluften. En annan erfarenhet från fältundersökningarna var att utfallen av berg och sprutbetong ofta förekom i sektioner som hade problem med vattenläckage.Resultaten från laborationsförsöken utförda i det här licentiatprojektet visar också att vatten i kombination med negativa temperaturer kan orsaka nedbrytningsproblem. De utförda dragtesterna visade att vidhäftnings-hållfastheten minskar med ungefär 50 % när sprutbetong/bergproverna hade utsatts för frysning. Vidare visade mätningarna av akustisk emission (AE) att fler AE-händelser skedde när sprutbetong/bergproverna hade tillgång till vatten under frysningen. Litteraturstudien, fältundersökningarna i järnvägstunnlarna och laborationsförsöken pekar på att tillgången på vatten under frysning kan orsaka skador på skiktet mellan berg och sprutbetong. Detta bekräftar hypotesen att utfall av berg och sprutbetong kan uppstå på grund av att istryck i en spricka eller i skiktet mellan berg och sprutbetong överskrider draghållfastheten för materialet eller vidhäftningshållfastheten mellan berg och sprutbetong. En sak som laborationsförsöken inte kunde ge ett bra svar på var ifall utfallen kunde ske på grund av spridning av en liten yta som redan från början hade dålig vidhäftning runt en spricköppning. Men försöken visade att det förekom mycket aktivitet under frysningen i de områden som preparerats med dålig vidhäftning. Så det verkar som att små områden med dålig vidhäftning kan påverkar försämringen av vidhäftningen mellan berg och sprutbetong.

  • 112.
    Andrén, Anna
    Luleå tekniska universitet.
    Degradation of rock and shotcrete due to ice pressure and frost shattering2006Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    På senare år har Banverket märkt en ökning av inrapporterade nedfall av berg och sprutbetong i sina järnvägstunnlar. I och med detta så startades en rad forskningsprojekt kring problemen med vattenläckage och isbildning i tunnlar. Detta projekt ”Nedbrytning av berg och sprutbetong på grund av istryck och frostsprängning” är ett av dessa. Syftet med denna rapport är att samla erfarenhet och information om hur is bildas samt hur istryck påverkar krosszoner, sprickor och skiktet mellan berg och sprutbetong. När vatten fryser till is sker en 9 % volymsutvidgning och denna expansion kan orsaka att ett tryck uppstår mot det omgivande materialet. Om vattnet befinner sig i ett litet innestängt område, exempelvis i en por eller i en sluten spricka som inte tillåter att en 9 % volymsutvidgning sker, kommer ett brott att uppstå i det omgivande materialet. Volymsutvidgningen som sker vid isbildning kan bara förhindras genom att trycksätta vattnet/isen med ett tryck från det omgivande materialet på 207 MPa, vilket motsvarar isens trycksmältpunkt. Som en jämförelse är draghållfastheten i berg ca 10 MPa vilket leder till att brott alltid kommer att uppstå i vattenmättat berg om vatten fryser i ett innestängt område. Det omgivande materialet kommer att utsättas för brott om trycket från isen överstiger materialets draghållfasthet, men storleken på skadan är bland annat beroende av materialets vattenmättnad. Ett delvis vattenmättat material kan klara sig från brott, trots att dess draghållfasthet är låg, genom att expansionen av isen och omfördelning av porvatten kan ske i de porer som från början var fyllda med luft. Ett helt vattenmättat material ger istället efter för frostsprängningen oberoende av sin draghållfasthet, på grund av att materialet inte har något fritt utrymme som kan ta upp expansionen. Men det är inte bara den 9 % volymsutvidgningen som orsakar frostsprängning. Forskning visar att om berg har tillgång till fritt vatten under nedkylningen, sker en process som liknar tjällyftning i jord. I jord vandrar vatten fram mot frysfronten och där bildas islinser. På ett liknande sätt verkar vatten vandra i berg och orsaka att iskroppar växer i porer och i sprickor. Vattenvandringen sker på grund av det faktum att det finns en tunn vattenfilm av adsorberat vatten längs ytorna av mineralkornen och i denna vattenfilm finns möjlighet för vatten att vandra mot frysfronten. Experimentellt arbete har visat att en betydande del av det adsorberade vattnet förblir ofruset vid negativa temperaturer, inte bara i jord utan även i berg och detta gynnar vattenvandringen. Men när temperaturen sjunker mer och mer börjar även det adsorberade vattnet i vattenfilmen att frysa och andelen ofruset vatten minskar. Så med sjunkande temperatur blir vattenfilmen, som separerar isen och mineralkornen, tunnare och tunnare. Detta reducerar vattenvandringen fram mot frysfronten. Om temperaturen fortsätter att sjunka, kan vattenvandringen avta helt och så även istillväxten. Vattenvandringen och istillväxten är inte bara beroende av tillgången till vatten och frystemperatur, utan även av fryshastighet och varaktighet av köldgrader. Om berget utsätts för snabb nedfrysning (hög fryshastighet) minskar vattenfilmens tjocklek fort och vattenvandringen förhindras, vilket begränsar frostsprängning av berget. Om istället berget kyls ned långsamt (låg fryshastighet), tillåts vattenvandring att ske under en längre period, vilket kan resultera i större frostsprängning av berget.

  • 113.
    Andrén, Anna
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dahlström, Lars-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Temperaturflöden i järnvägstunnlar – Glödberget2011Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Under vinterhalvåret orsakar is stora problem i flera av Trafikverkets järnvägstunnlar. Vatten som fryser bildar istappar och svallis som kan fall ned i spår samt växa till sådan storlek att de inkräktar på det ”fria rummet” som tågen kräver för att passera genom tunneln. Belysningsarmaturer och kablar bryts sönder på grund av islast och spåren blir isbelagda på grund av takdropp och svallisbildning. Återkommande frysperioder medför att berg och sprutbetong i tak och väggar kan lossna och falla ner. För att upprätthålla säkerheten och förhindra trafikstörningar kräver många tunnlar omfattande underhållsinsatser. För att kunna reducera underhållet i tunnlarna, krävs förbättrad kunskap kring köldinträngning och effekterna av istryck på det bärande huvudsystemet. 2002 utförde Högskolan i Gävle och KTH en modellstudie för att bestämma temperatur-förhållanden i tunnlar. För att verifiera modellstudien genomförs nu mätningar i fält och projektet utförs i ett samarbete mellan Trafikverket och Luleå Tekniska Universitet. Denna Tekniska rapport redovisar de mätningar som hittills utförts i Glödbergstunneln vid Nyåker som ligger 8 mil sydväst om Umeå. Mätningarna visar att framtagna modeller underskattar köldinträngningen. Trots att tunneln är 1680 m lång, sker köldinträngning i hela tunnelns längd även vid några få minusgrader utanför tunneln. En bidragande orsak till att fältmätningarna och modellen inte överensstämmer kan vara att modellstudien bygger på en helt oisolerad tunnel. I Glödbergstunneln finns en stor del frostisolerande dräner uppsatta. De frostisolerande dränernas funktion är att förhindra att inläckande vatten fryser till is, men isoleringen förhindrar inte bara kylan att tränga in till läckaget, den hindrar även bergvärmen från att komma ut i tunneln och värma upp den kalla uteluften. Isoleringen möjliggör för kylan att tränga längre in i tunneln än vad den skulle ha gjort i fall bergvärmen gavs möjlighet att värma upp den kalla uteluften på dess väg in längs tunneln. Mängden frostisolerande dräner och hur stor del av tunnels vägg- och takyta som är inklädd, täckningsgraden, påverkar därmed köldinträngningens längd. Mätningar av temperaturer har utförts ned i ballasten. Glödbergstunneln har en undersprängning på 2 m under RUK, med motiveringen att ledningar för exempelvis dräneringsvatten ska vara förlagda på frostfritt djup. Mätningarna visar att temperaturen inte tränger så långt ned som man tidigare befarat och undersprängning i de mittersta delarna av tunneln hade kunnat göras mindre, med avseende på frostrisken. Temperaturmätningarna bakom en frostisolerad drän i mitten av spårtunneln, har visat att dränen klarar av att jämna ut de temperaturväxlingar som sker i tunnelluften utanför dränen. Men då temperaturen är negativ under en längre period kryper även temperaturen bakom dränen under 0 C och då förhindras dräneringsmöjligheten på grund av isbildning och det kan orsaka frostsprängning av dränen. Mätningar av lufttemperatur i den intilliggande servicetunneln visar tydligt hur köldinträngningen påverkas av luftrörelser. Servicetunneln är stängd med portar mot både ute- och tunnelluft. När luften i en tunnel inte utsätts för rörelse, värms den upp av bergvärmen och antar samma temperatur som berget har. Bergtemperaturen brukar oftast sammanfalla men den årsmedeltemperatur som gäller för den plats där tunneln är belägen. För Glödbergstunneln stämmer detta mycket bra överens med de utförda mätningarna i servicetunneln. Sökord: köldinträngning, istryck, frostsprängning, temperaturmätning, underhåll, järnvägstunnel.

  • 114.
    Andrén, Anna
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dahlström, Lars-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Temperaturflöden i järnvägstunnlar och konsekvenser för drift och underhåll2008Ingår i: Bergmekanikdag: föredrag vid Bergmekanikdag i Stockholm 10 mars 2008, Stiftelsen bergteknisk forskning - Befo , 2008Konferensbidrag (Övrigt vetenskapligt)
  • 115. Appelgren, J
    et al.
    Schunnesson, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nord, G
    Automation and smart drill rigs2006Ingår i: Mine planning and equipment selection 2006: Fifteenth International Symposium on Mine Planning & Equipment Selection / [ed] Marilena Cardu ; Enrica Michelotti, Fiordo , 2006Konferensbidrag (Refereegranskat)
  • 116.
    Arasteh Khouy, Iman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Cost-effective maintenance of railway track geometry: a shift from safety limits to maintenance limits2013Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Railway infrastructure is a complex system which comprises different subsystems. Long life span is one of the important aspects of this prime mode of transport. However, the useful life of its assets is highly dependent on the maintenance and renewal strategy used during the assets’ life cycle. Today’s demands on the railway industry call for increased capacity, including more trains, travelling at higher speeds with higher axle loads. This increased usage results in higher degradation of railway assets and higher maintenance costs. Formerly, railway maintenance procedures were usually planned based on the knowledge and experience of the infrastructure owner. The main goal was to provide a high level of safety, and there was little concern for economic issues. Today, however, the deregulated competitive environment and budget limitations are forcing railway infrastructures to move from safety limits to cost-effective maintenance limits to optimise operation and maintenance procedures. The goal is to make operation and maintenance cost-effective while still meeting high safety standards.One of the main parameters to assure railway safety and comfortable railway service is to maintain high quality of track geometry. Poor quality of track geometry, directly or indirectly, may result in safety problems, speed reduction, traffic disruption, greater maintenance cost and higher degradation rate of the other railway components (e.g. rails, wheels, switches and crossings etc.). The aim of this study is to develop a methodology to optimise track geometry maintenance by specifying cost-effective maintenance limits. The methodology is based on reliability and cost analysis and supports the maintenance decision-making process. The thesis presents a state-of-the-art review of track geometry degradation and maintenance optimisation models. It also includes a case study carried out on the iron ore line in the north of Sweden to analyse the track geometry degradation and discuss possible reasons for the distribution of failures along the track over a year. It describes Trafikverket’s (Swedish Transport Administration) maintenance strategy regarding measuring, reporting on and improving track quality, and it evaluates the efficiency of this strategy. It introduces two new approaches to analyse the geometrical degradation of turnouts due to dynamic forces generated from train traffic. In the first approach, the recorded measurements are adjusted at crossing point and then the relative geometrical degradation of turnouts is evaluated by using two defined parameters, the absolute residual area (ARa) and the maximum settlement (Smax). In the second approach, various geometry parameters are defined to estimate the degradation in each measurement separately. It also discusses optimisation of the track geometry inspection interval with a view to minimising the total ballast maintenance costs per unit traffic load. The proposed model considers inspection time and the maintenance-planning horizon time after inspection and takes into account the costs associated with inspection, tamping and risk of accidents due to poor track quality. Finally, it proposes a cost model to identify the cost-effective maintenance limit for track geometry maintenance. The model considers the actual longitudinal level degradation rates of different track sections as a function of million gross tonnes (MGT) / time and the observed maintenance efficiency.

  • 117.
    Arasteh khouy, Iman
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Optimization of track geometry maintenance: a study of track geometry degradation to specify optimal inspection intervals2011Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Railway infrastructure is a complex system which comprises different subsystems. Long useful life span is one of the important aspects of this prime mode of transport. The useful life length of its assets is highly dependent on the maintenance and renewal strategy used during its life cycle. Today’s demands on the railway industry call for increased capacity, including more trains, travelling at higher speeds with higher axle loads. This increased usage will result in higher degradation of railway asset and higher maintenance costs. However, due to the competitive environment and limited budgets, railway infrastructure managers are compelled to optimize operation and maintenance procedures to decrease operation and maintenance costs while meeting high safety standards. To assure track safety and maintain high quality, a cost effective track maintenance strategy is required, one based not only on technical and/or safety limits but also on cost-effective maintenance thresholds. RAMS (Reliability, Availability, Maintainability and Safety) and LCC (Life Cycle Cost) analyses, which are derived from reliable track condition data, provide an approach to specify cost effective maintenance strategy to lessen corrective maintenance actions and downtimes.One of the main parameters to assure railway safety and comfortable railway service is to maintain high quality of track geometry. Poor track geometry quality, directly or indirectly, may result in safety problems, speed reduction, traffic disruption, greater maintenance cost and higher degradation rate of the other railway components (e.g. rails, wheels, switch, crossings etc.). The aim of this study is to develop a methodology to optimize track geometry maintenance by using historical geometry data. The methodology is based on reliability and cost analysis and supports the maintenance decision-making process to identify cost-effective inspection interval. An important phase of track geometry maintenance optimization is to estimate the track degradation rate. Obtaining knowledge about degradation helps to properly schedule maintenance activities such as inspection and tamping.The thesis provides a methodology to identify a cost-effective inspection interval based on track degradation rate and cost drivers. It contains state-of-the-art track geometry maintenance optimization. It describes Trafikverket’s (Swedish Transport Administration) maintenance strategy regarding measurements, reporting on and improving track quality, and it evaluates the efficiency of this strategy. Finally, it includes a case study carried out on the iron ore line in north of Sweden that runs from Boden to Gällivare to evaluate track geometry degradation and analyze the probability distributions of failures. A cost model is developed in order to find optimal inspection interval.Keywords: Track geometry degradation, Track maintenance optimization, Maintenance planning, Tamping

  • 118.
    Arasteh khouy, Iman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Larsson-Kråik, Per-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nissen, Arne
    Trafikverket.
    Juntti, Ulla
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Schunnesson, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Optimisation of track geometry inspection interval2014Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 228, nr 5, s. 546-556Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The measurement and improvement of track quality are key issues in determining the time at which railway maintenance must be performed and its cost. Efficient track maintenance ensures optimum allocation of limited maintenance resources which has an enormous effect on maintenance efficiency. Applying an appropriate tamping strategy helps reduce maintenance costs, making operations more cost-effective and leading to increased safety and passenger comfort levels. This paper discusses optimisation of the track geometry inspection interval with a view to minimising the total ballast maintenance costs per unit traffic load. The proposed model considers inspection time, the maintenance-planning horizon time after inspection and takes into account the costs associated with inspection, tamping and risk of accidents due to poor track quality. It draws on track geometry data from the iron ore line (Malmbanan) in northern Sweden, used by both passenger and freight trains, to find the probability distribution of geometry faults.

  • 119.
    Arasteh khouy, Iman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Larsson-Kråik, Per-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nissen, Arne
    Trafikverket.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Cost-effective track geometry maintenance limits2016Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 230, nr 2, s. 611-622Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the past, railway maintenance actions were usually planned based on the knowledge and experience of the infrastructure owner. The main goal was to provide a high level of safety, and there was little concern about economic and operational optimisation issues. Today, however, a deregulated competitive environment and budget limitations are forcing railway infrastructures to move from safety limits to cost-effective maintenance limits to optimise operation and maintenance procedures. By so doing, one widens the discussion to include both operational safety and cost-effectiveness for the whole railway transport system. In this study, a cost model is proposed to specify the cost-effective maintenance limits for track geometry maintenance. The proposed model considers the degradation rates of different track sections and takes into account the costs associated with inspection, tamping, delay time penalties, and risk of accidents due to poor track quality. It draws on track geometry data from the Iron Ore Line (Malmbanan) in northern Sweden, used by both passenger and freight trains, to estimate the geometrical degradation rate of each section. The methodology is based on reliability and cost analysis and facilitates the maintenance decision-making process to identify cost-effective maintenance thresholds.

  • 120.
    Arasteh khouy, Iman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Larsson-Kråik, Per-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nissen, Arne
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Geometrical degradation of switches and crossings on a Swedish heavy haul railroad: a case study2013Ingår i: Proceedings of 10th International Heavy Haul Association Conference, New Delhi, India, 2013, Vol. 1, s. 26-32Konferensbidrag (Refereegranskat)
    Abstract [en]

    Switches and crossings (S&Cs) are one of the most critical components of railway track systems in terms of safety, operation and maintenance. Each year, a considerable part of the maintenance budget is spent on inspection, maintenance and renewal of S&Cs. However, applying a cost-effective maintenance strategy helps to achieve the best performance at the lowest possible cost. In Sweden, the geometry of S&Cs is inspected at pre-defined time intervals by the STRIX track measurement car. In this paper, time series for the measured longitudinal level of S&Cs on the Iron Ore Line (Malmbanan) in northern Sweden have been used. Two parameters have been defined in this study, namely the absolute residual area (ARa) and the maximum settlement (Smax), to analyse the geometrical degradation of switches and crossings due to dynamic forces generated from train traffic. The paper also evaluates the growth rate of the longitudinal level degradation as a function of million gross tonnes (MGT). The results facilitate correct decision making in the maintenance process through understanding the degradation rate and defining the optimal maintenance thresholds for the planning process. In the long run this will lead to a cost-effective maintenance strategy with optimized inspection and maintenance intervals.

  • 121.
    Arasteh khouy, Iman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Larsson-Kråik, Per-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nissen, Arne
    Trafikverket.
    Lundberg, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Kumar, Uday
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Geometrical degradation of railway turnouts: a case study from a Swedish heavy haul railroad2014Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 228, nr 6, s. 611-619Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Turnouts are critical components of track systems in terms of safety, operation and maintenance. Each year, a considerable part of the maintenance budget is spent on their inspection, maintenance and renewal. Applying a cost-effective maintenance strategy helps to achieve the best performance at the lowest possible cost. In Sweden, the geometry of turnouts is inspected at predefined time intervals using the STRIX / IMV 100 track measurement car. This study uses time series for the measured longitudinal level of turnouts on the Iron Ore Line (Malmbanan) in northern Sweden. Two different approaches are applied to analyse the geometrical degradation of turnouts due to dynamic forces generated by train traffic. In the first approach, the recorded measurements are adjusted at the crossing point and then the relative geometrical degradation of turnouts is evaluated by using two defined parameters, the absolute residual area and the maximum settlement, In the second approach, various geometry parameters are defined to estimate the degradation in each measurement separately. The growth rate of the longitudinal level degradation as a function of million gross tonnes / time is evaluated. The proposed methods are based on characterisation of the individual track measurements. The results facilitate correct decision-making in the maintenance process through understanding the degradation rate and defining the optimal maintenance thresholds for the planning process. In the long run, this can lead to a cost-effective maintenance strategy with optimised inspection and maintenance intervals.

  • 122.
    Arasteh khouy, Iman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Schunnesson, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Juntti, Ulla
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Nissen, Arne
    Larsson-Kråik, Per-Olof
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Evaluation of track geometry maintenance for heavy haul railroad in Sweden: a case study2014Ingår i: Proceedings of the Institution of mechanical engineers. Part F, journal of rail and rapid transit, ISSN 0954-4097, E-ISSN 2041-3017, Vol. 228, nr 5, s. 496-503Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The measurement and improvement of track quality are key issues in determining both the restoration time and cost of railway maintenance. Applying the optimal tamping strategy helps reduce maintenance costs, making operations more cost effective and leading to increased safety and passenger comfort. In this paper, track geometry data from the iron ore line (Malmbanan) in northern Sweden, which handles both passenger and freight trains, are used to evaluate track geometry maintenance in cold climate. The paper describes Trafikverket’s (Swedish Transport Administration) tamping strategy and evaluates its effectiveness in measuring, reporting, and improving track quality. Finally, it evaluates the performance of the maintenance contractor and discusses the importance of the functional requirements stated in the outsourcing contracts.

  • 123.
    Arasteh khouy, Iman
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Schunnesson, Håkan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Nissen, Arne
    Trafikverket.
    Juntti, Ulla
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Evaluation of track geometry degradation in Swedish heavy haul railroad: a case study2012Ingår i: International Journal of COMADEM, ISSN 1363-7681, Vol. 15, nr 2, s. 11-16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The measurement and improvement of track quality are key issues in determining both the time and cost of railway maintenance. Efficient track geometry maintenance ensures optimum allocation of limited maintenance resources and has an enormous effect on maintenance efficiency. Applying the appropriate tamping strategy also helps reduce maintenance costs, making operations more cost effective and leading to increased safety and passenger comfort. In this paper, track geometry data from the iron ore line in northern Sweden, which handles both passenger and freight trains, are used to calculate track quality degradation trend in a cold climate. The paper describes Trafikverket’s (Swedish Transport Administration) tamping strategy and illustrates the distribution of safety failures in different seasons. It also analyses the track geometry degradation and discuss about the possible reasons for distribution of failures over a year and along the track.

  • 124. Arvanitidis, Ioannis
    et al.
    Nyberg, Ulf
    Ouchterlony, Finn
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Diameterns inverkan på detonationsegenskaperna hos emulsionssprängämne E682 i cylinderprovet2004Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    Cylindertest har genomförts på emulsionssprängämne 682 (E682) i syfte att undersöka hur arbetsförmågan varierar med laddningsdiametern inom intervallet 40-100 mm. Två satser syrebalanserad emulsion undersöktes, ren E682 och E682 med 20% ANFO. Receptet till E682 är framtaget tillsammans med Dyno Nobel och Kimit AB. Denna experiment emulsion har undersökts tidigare, bl.a. finns en brinnmodell. Emulsionen är syrebalanserad. När det gäller den volymbaserade explosionsenergin så ligger ren E682 något lägre än E682 med 20% ANFO, 3.47 MJ/dm3 respektive 3.85 MJ/dm3. Mjukglödgade 1 m långa kopparrör med inner/ytter diametrar 40/44, 60/66, 80/88 och 100/110 (mm/mm) har använts. Försöksuppställningen består av ett vertikalt monterat kopparrör fyllt med E682. Laddningsdensiteten var ca 1130 och 1200 kg/m3 för ren E682 respektive E682 med 20% ANFO. Initieringen sker ovanifrån med sprängdeg varvid detonationsfronten går nedåt genom laddningen i röret. Detonationsfrontens hastighet (VOD) mäts med resistansprob som monterats längs rörets mittlinje. Den radiella expansionen mäts med 10 kontaktpinnar ca 65 cm nedåt på röret ifrån initieringspunkten. Expansionen mäts från 0.5 mm från rörväggen till en total volymexpansion om 6-9ggr. Med hjälp av VOD och expansionsdata kan man räkna fram kopparväggens rörelse och den kinetiska slutenergin kallad "Gurneyenergin" som är ett mått på sprängämnets arbetsförmåga. Genom att jämföra Gurneyenergin med explosionsenergin kan man få fram en verkningsgrad. Gurneyenergin, som mäts i MJ/kg sprängämne, var oberoende av laddningsdiametern. Följden blir att även verkningsgraden är oberoende av laddningsdiametern inom det studerade intervallet 40-100 mm. För ren emulsion låg kopparväggens sluthastighet runt 1280 ± 20 m/s och Gurneyenergin 1.77 ± 0.06 MJ/kg. Vad gäller E682 med 20 % ANFO blev hastigheten något högre, 1290 ± 20 m/s samt Gurneyenergin 1.71 ± 0.07 MJ/kg. Verkningsgraden för ren E682 är 58 ± 3 % och för E682 med 20 % ANFO 53 ± 3% av tillgänglig energi. Den något lägre verkningsgraden för E682 med 20 % ANFO kan förklaras med att ANFO i sig har en lägre verkningsgrad ca 40-50 %. En tidigare försöksserie av Nie (2001) visade förvånansvärt nog verkningsgraden hos försöken med 80/88 rören var markant högre än hos 40/44 och 100/110 rören. I jämförelse med denna studie så verkar sluthastigheterna i Nie's försök med 80/88 rören vara onormalt höga vilket kan tänkas bero på materialfel eller dimensionsfel hos rören. Man kan tydligt se att kopparväggens acceleration ökar med minskande rördiameter. Detta är en naturlig följd av att massan som ska accelereras minskar mycket snabbare med minskande laddningsdiameter än vad detonationstrycket gör. Sammanfattningsvis kan man säga att verkningsgraden minskar något för E682 då man tillsätter ANFO men att den är oberoende av laddningsdiametern. Om man jämför Gurneyenergin på volymbasis så ligger däremot ren E682 obetydligt lägre än E682 med 20% ANFO, ca 2%.

  • 125.
    Ask, D.
    et al.
    Vattenfall Power Consultant AB, Luleå.
    Stephansson, O.
    GeoForschungsZentrum Potsdam.
    Cornet, F.H.
    Institut de Physique du Globe de Strasbourg.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rock stress, rock stress measurements, and the Integrated Stress Determination Method (ISDM)2009Ingår i: Rock Mechanics and Rock Engineering, ISSN 0723-2632, E-ISSN 1434-453X, Vol. 42, nr 4, s. 559-584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The primary objectives of this work are to (1) improve the understanding of the prevailing stress distribution at the Äspö Hard Rock Laboratory (HRL) in SE Sweden by employing an integrated stress determination approach, and in order to accomplish this (2) extend the existing stress integration methodology denominated integrated stress determination method (ISDM; Cornet in Comprehensive Rock Engineering vol 3, Pergamon Press, Oxford, pp 413-432, 1993a). The new developments of the ISDM involve a 12-parameter representation of the regional stress field in the rock mass (i.e., the full stress tensor and its variation with depth) that is applicable to hydraulic stress data (sleeve fracturing, hydraulic fracturing, and hydraulic tests on pre-existing fractures), overcoring data (CSIR- and CSIRO-type of devices), and to combinations of hydraulic and overcoring stress data. For the latter case, the elastic parameters of the overcoring technique may be solved in situ by allowing the hydraulic stress data to constrain them. As a result, the problem then involves 14 model parameters. Results from the study show that the ISDM effectively improves the precision of the prevailing stress field determination and that it is especially powerful for identification of consistencies/inconsistencies in an existing data set. Indeed, this is the very basic premise and goal of stress integration; combine all available data to achieve as complete a characterization of the mechanical stress model as possible, and not to identify a solution that fits only loosely the maximum amount of stress data.

  • 126.
    Ask, Daniel
    Luleå tekniska universitet.
    Evaluation of measurement-related uncertainties in the analysis of overcoring rock stress data from Äspö HRL, Sweden: a case study2003Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 40, nr 7-8, s. 1173-1187Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A re-evaluation of overcoring results from the Borre Probe and the CSIRO HI cell was carried out at the Äspö HRL. The re-analysis revealed a number of measurement-related uncertainties for the two cells, e.g. bonding, temperature effects and identification of elastic parameters. These uncertainties were corrected and the re-analyzed strains were then used to determine the in situ stress field using standard least-squares technique. The results indicate lower stress magnitudes compared to the original interpretations and the results are in good agreement with existing hydraulic fracturing data as well as with theoretical vertical stress. Overall, the re-analysis indicates that the stress field at Äspö HRL is well constrained and relatively consistent with depth.

  • 127.
    Ask, Daniel
    Luleå tekniska universitet.
    Measurement-related uncertainties in overcoring data at the Äspö HRL, Sweden: Part 2: Biaxial tests of CSIRO HI overcore samples2006Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, nr 1, s. 127-138Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper is the second dealing with measurement-related uncertainties of overcoring data undertaken at the Äspö Hard Rock Laboratory and focuses on the biaxial test data from CSIRO HI overcore samples. The first paper dealt with measurement-related uncertainties in connection with the overcoring phase [1]. The uncertainties identified in connection to biaxial tests of CSIRO HI overcore samples include too large applied pressures and poor sampling frequency. At the Aspo HRL, the results yield that most overcore samples fractured during biaxial testing, meaning that a significant part, 56%, of available strain gauge combinations were removed from calculations of the elastic parameters. Remaining strain gauge combinations indicate average values of 62′5 GPa for Young's modulus and 0.25′0.01 for Poisson's ratio, which are considerably lower than previously published values [2-5], and are in good agreement with results from biaxial tests on Borre Probe overcore samples .[6-10]. The stress calculations were obtained from re-analyzed elastic parameters and strains, and show primarily a reduction in stress magnitudes. Overall, the stress field obtained with different stress measurement methods and its variation with depth is now quite well resolved. The overcoring data suggest that the principal stresses are inclined with a vertical component dipping about 65° from the horizontal over the investigated rock volume (140-420 m depth). This is interpreted as a result of influence from the sub-vertical NE-2 Fracture Zone that divides the stress data into two stress domains [11], although it may also be an artefact because the σ[2]- and σ[3]-magnitudes are of the same order of magnitude.

  • 128.
    Ask, Daniel
    Luleå tekniska universitet.
    New developments in the integrated stress determination method and their application to rock stress data at the Äspö HRL, Sweden2006Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 43, nr 1, s. 107-126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Integrated Stress Determination Method (ISDM) is a powerful tool for estimating the regional stress tensor from in-situ measurements of local stress tensors using a wide variety of stress measuring techniques. This study presents new developments of the ISDM: The stress field may be described with up to 12 model parameters; and is applicable to data from CSIR- and CSIRO HI-type of overcoring devices, hydraulic fracturing, hydraulic tests of pre-existing fractures (HTPF), as well as to combined data sets. Furthermore, in combined data sets, the hydraulic fracturing and/or HTPF data may be used to constrain the average elastic parameters, Young's modulus and Poisson's ratio. The new ISDM developments were applied to the extensive and recently re-analysed rock stress data at the Äspö Hard Rock Laboratory. The results reveal a good fit of the re-analysed data. Overall, the re-analysis indicates that the stress field at Äspö HRL is relatively well constrained and consistent with depth. The NE-2 Fracture Zone influences the stresses, and dividing the regional stress field into a NW and a SE stress domain. When the hydraulic fracturing data were used to constrain the average elastic parameters, Young's modulus, E, and Poisson's ratio, ν, quite similar results were obtained (E=50.8 GPa and v=0.33) compared with results from biaxial tests of overcore samples (E=61.6 MPa and v=0.26).

  • 129.
    Ask, Daniel
    et al.
    Vattenfall Power Consultant AB, Luleå.
    Cornet, F.H.
    Institute de Physique du Globe de Strasbourgh.
    Fontbonne, F.
    GEO-energies, Clermont-Ferrand.
    Nilsson, Tommy
    Jönsson, L.
    Hydraulikmontage i Luleå AB.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    A quadruple packer tool for conducting hydraulic stress measurements in mines and other high stress settings2009Ingår i: International Journal of Rock Mechanics And Mining Sciences, ISSN 1365-1609, E-ISSN 1873-4545, Vol. 46, nr 6, s. 1097-1102Artikel i tidskrift (Refereegranskat)
  • 130.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Data report: consolidation state and stress ratio of clay-rich sediments from Site U13202009Ingår i: Proceedings of the Integrated Ocean Drilling Program, ISSN 1930-1014, Vol. 308Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Overpressure and fluid flow processes in the deepwater Gulf of Mexico were investigated during Expedition 308 of the Integrated Ocean Drilling Program.This data report presents the results from a reconsolidation test that was carried out on a clay-rich sample from the base of Brazos-Trinity Basin IV, at 276.40 m below seafloor. The sample was subjected to a stress path of uniaxial strain (K0 reconsolidation), and the test was conducted in an advanced triaxial cell under drained conditions. Posttest investigation revealed that the sample was disturbed by drilling. The results should be interpreted with care.The sample was loaded to a total effective vertical stress, σv′, of 24 MPa, corresponding to effective horizontal stress, σh′, of >16 MPa and vertical strain, εv, of 16%. The results propose an effective vertical yield stress of 2.03 MPa, which suggests a maximum pore fluid pressure in excess of hydrostatic water pressure of 0.24 MPa. Furthermore, the ratio between effective horizontal and vertical stresses is rather constant, ~0.7, even at high stress magnitudes.

  • 131. Ask, Maria
    In situ stress at the Cote d'Ivoire-Ghana marginal ridge from FMS logging in Hole 959D1998Ingår i: Proceedings of the Ocean Drilling Program. Scientific results, College Station, TX, 1998, s. 209-223Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The orientation of the in situ stress between 550 and 925 meters below seafloor in Hole 959D has been derived from the analysis of caliper and electrical images of Formation MicroScanner data. Because of a high hole deviation (5°-13°), drill pipe wear has enlarged the hole in a northerly direction. As a result, the four-arm caliper analyses cannot distinguish between mechanically and stress induced borehole elongations. The FMS data show that one of the principal stresses is parallel to the borehole axis and that mainly tensile wall fractures have formed in the borehole wall. The tensile wall fractures demonstrate a 168° ± 8°N weighted mean orientation of the maximum horizontal stress. The upper 750 mbsf of the borehole comprises the majority of the tensile wall fractures, whereas they only occur sporadically below this depth. The change in the downhole distribution of fractures coincides with the transition from weaker to more compacted, stronger sedimentary rock. Furthermore, the integration of seismic and physical properties data suggests that this depth corresponds to the boundary between passive margin evolution and continent/ocean transform faulting. The orientation of the maximum horizontal stress in Hole 959D is almost perpendicular to the east-west maximum horizontal stress orientation of the first-order stress province in western and north central Africa. Through comparisons with (1) the orientations of the maximum horizontal stress in Hole 959D, (2) the maximum horizontal stress of three focal mechanisms from earthquakes in Ghana, and (3) the strike of the continental margin, it is suggested that lateral strength contrasts across the Côte d’Ivoire-Ghana Transform Margin are the most probable source for the observed stress orientations. It is further suggested that sediment loading and lateral variation in crustal thickness and density may only have a minor influence on the stress field in this area.

  • 132. Ask, Maria
    In situ stress from borehole breakouts in Denmark1996Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
  • 133. Ask, Maria
    In-situ and laboratory stress investigations using borehole data from the North Atlantic Ocean1998Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This doctoral thesis presents results from investigations ofin-situ and laboratory stress from borehole logging andlaboratory deformation experiments on drill-cores. The datacome from hydrocarbon exploration and production wells in theDanish Sector of the North Sea, and from boreholes drilled bythe Ocean Drilling Program (ODP). The drill-core samples werecollected from two ODP boreholes in the equatorial and easternAtlantic Ocean. The objectives for this project are: (1) to collect datafrom the North Atlantic Ocean where few or no stressmeasurements exist, and to incorporate the data into the WorldStress Map (WSM); (2) to determine the source of stress thatgenerates the mean orientation of the maximum horizontal stressin individual boreholes in ocean areas; and (3) to study themechanical responses of sediments and rocks in order tounderstand the nature of stress and stress paths that producedeformation of the ocean floor. The orientations of in-situ horizontal stresses weredetermined from analyses of borehole breakouts anddrilling-induced fractures (DIFs) as determined from four-armcaliper and Formation MicroScanner (FMS) data. Logging datawere analyzed using graphical and automated programs, usingbreakout and DIF criteria, directional statistics, and theborehole data were ranked according the WSM ranking system. Stress data from 44 oil wells and ODP boreholes in the NorthAtlantic Ocean represent important additions to the WSM fromareas where few stress data were available. Despite of theirrelatively shallow total depths, it is suggested that thestress orientation in many of the ODP boreholes are influencedby plate boundary forces. The observed variation in downholedistribution of breakouts in the oil wells and the lack ofregional trends indicate that local and regional stress sourcescontrol the stress field in these wells. Detailed laboratory stress measurements were conducted in atriaxial cell mounted in a servo-hydraulic load frame, usingreconsolidation and triaxial tests on small sub-samples fromtwo drill-core samples of different lithologies. Results from tests on a claystone from the basal section ofthe ocean-continent transition in West Iberia margin suggestthat the in-situ effective stresses are low because of the highpore pressure. The fractured nature of the underlying basementand breccia suggest that the pore fluids originate from deepersections. Results from tests on a calcarenite from about 1 kmdepth show that the elastic versus elastic-plastic behaviordiffers significantly, but that the rock behavior can bedescribed by critical state soil mechanics.

  • 134. Ask, Maria
    In-situ stress from breakouts in the Danish sector of the North Sea1997Ingår i: Marine and Petroleum Geology, ISSN 0264-8172, E-ISSN 1873-4073, Vol. 14, nr 3, s. 231-243Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Borehole breakouts from 26 wells situated in the Danish Central Graben and one well situated in the northwestern section of the Ringkobing-Fyn High have been studied. The data provide information on the orientation of the contemporary principal horizontal stresses down to depths of 4.7 km. Statistics were used to obtain a mean azimuth of breakouts for each well, and each individual breakout was weighted by its length. Data quality of breakouts is assigned according to the World Stress Map quality ranking scheme. The breakout data reveal that SH orientations in the Danish Central Graben are extremely scattered; no regional trend in mean SH orientation can be identified as a result of the large standard deviation (±77°). Similar scatterings of SH orientations have been reported from adjacent regions of the North Sea. The results indicate that the state of stress in the sedimentary cover of the Danish Central Graben is influenced by a local stress generating mechanism rather than platewide stress transmissions mechanisms. Three units with different states of stress have been identified and found to correspond somewhat with the lithostratigraphic divisions of the Post Chalk Group, Chalk Group and Pre Chalk Group.

  • 135. Ask, Maria
    Mechanical tests on claystone from Ocean Drilling Program Hole 1070A (Leg 173): implications for elevatedpore-fluid pressure in sediments within the ocean-continent transition zone, West Iberia2001Ingår i: Marine Geology, ISSN 0025-3227, E-ISSN 1872-6151, Vol. 177, nr 3, s. 395-410Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laboratory geotechnical deformation tests on a claystone test specimen from 619 m depth in Ocean Drilling Program Hole 1070A provide evidence of low effective yield stresses and capillary pressures (1.2–1.5 MPa) in the sediment section near the acoustic basement. Effects from negative pore-fluid pressure, and the presence of expansive clay minerals probably account for the drastic change in the mechanical behavior of the sample below and above the yield stress. The results from the geotechnical tests, together with high porosity values, suggest that the pore-fluid pressure is high in these basal sediments. The intense fracture/vein development in the basement suggests that the pore-fluids originate from deeper sections in the basement. Porosity anomalies are found near the basement in three boreholes drilled in the western part of the Iberia Margin. The anomalies are interpreted to signal elevated pore-fluid pressure. Consequently, a zone of overpressure possibly exists in the western part of the ocean-transition zone of the West Iberia margin, which thickens towards the west.

  • 136.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Project: Assessing the state of in-situ stress, deformation properties and consolidation processes in marine clay-rich sediments at the Nankai accretionary prism2010Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    Some of Earth's largest earthquakes occur along décollement faults that separate overriding plate and accretionary prism from subducting plate. I conduct a collaborative experimental study to assess in-situ stress state, deformation properties, and consolidation processes in clay-rich sediments from the Nankai accretionary prism (NAP), SE Japan. Some of these sediments will ultimately pass into the seismogenic zone where earthquakes are generated.

  • 137.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Technological Drivers for Future IODP Science: Progressing from application-specific to systematic technological development2009Konferensbidrag (Refereegranskat)
    Abstract [en]

    Since its inception with the Deep Sea Drilling Project (DSDP) scientific ocean drilling has always had a technology development component. Technology development has been critical for advancing ocean drilling and scientific progress would not have occurred without it. Resolution of the simpler technical problems have progressed satisfactorily through an application-specific process, however the more difficult and complex problems that limit achieving many of the scientific objectives of the Initial Science Plan (ISP) and active IODP drilling proposals remain unresolved and will require a more comprehensive and systematic effort. This White Paper highlights key technological/scientific goals identified by the Engineering Development Panel (EDP)-Improving Core Recovery and Quality; Addressing Geohazards; Microbiology in the Marine Subsurface Environment; Drilling to the Moho and Other Complex Drilling Projects; and Virtual Staffing-that are derived from the EDP Technology Roadmap v. 3.0 (http://www.iodp.org/eng-dev), the ISP, and active drilling proposals; and reinforced by the Science and Technology Panel (STP) Roadmap (v. 0.93). They offer the greatest promise for transforming scientific ocean drilling. In order to accomplish some of these goals, large-scale engineering developments will be necessary to deliver the transformational science needed by any drilling program beyond 2013.

  • 138.
    Ask, Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geovetenskap och miljöteknik.
    Ask, Daniel
    Sverige.
    Project: Detection of potential borehole breakouts in boreholes2010Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    This project investigates the occurrence of stress-induced borehole breakouts in two boreholes at the Forsmark site, KFM01A and KFM01B, that are 500 and 1000 m deep, respectively. The primary objective was to investigate if borehole breakouts are formed in Forsmark. The results confirm the occurrence of stress-induced features, and borehole boreholes were detected between 116 and 997 m vertical depth (mvd) in the two boreholes.

  • 139.
    Ask, Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Ask, Daniel
    Vattenfall Power Consultant AB, Luleå.
    Christiansson, R.
    Swedish Nuclear Fuel and Waste Management Co.
    Detection of borehole breakouts at the Forsmark site, Sweden2006Ingår i: In-situ rock stress: measurement, interpretation and application : proceedings of the International Symposium on In-situ Rock Stress, Trondheim, Norway, June 19-21, 2006/ / [ed] Ming Lu, London: Taylor and Francis Group , 2006, s. 79-86Konferensbidrag (Refereegranskat)
    Abstract [en]

    The objective of this paper was to investigate if borehole breakouts exist at the Forsmark investigation site of the Swedish Nuclear Fuel and Waste Management Co. Breakouts generally form when the stress concentration around the borehole exceeds the rock strength of the borehole wall, and result in borehole failure in the direction parallel to the minimum horizontal stress in vertical boreholes. Borehole televiewer and borehole image processing system data in boreholes KFM01A and KFM01B have been analyzed. The analyzes reveal that breakouts appear over 30-40% of the length of the investigated boreholes. The breakouts appear with both shallow- and deep-failure depths, where the overwhelming majority is of the shallow failure type. The scope of this initial study does not include the full characterization of identified breakouts and it is not clear at this stage as to the origin of the breakouts, i.e. if they are stress and/or drilling induced

  • 140. Ask, Maria
    et al.
    Beslier, Marie-Odile
    Boillot, Gilbert
    Ocean-continent boundary in the Iberia Abyssal Plain from multichannel seismic data1993Ingår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 218, nr 4, s. 383-393Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Ocean-Continent Boundary of the West Iberia margin is marked by a basement ridge trending N-S. Four segments of this ridge are recognized, each of them being progressively offset westward from 40°N to 43°N. Because the setting and seismic character of the ridge in the Iberia Abyssal Plain are similar to those of the Galicia margin ridge, which is made of serpentinized peridotite, we think that the southern segments of the ridge are also made of the same mantle material. The segmentation of the ridge suggests that the northward propagation of the continental break-up during the North Atlantic opening in Early Cretaceous times was discontinuous, each segment possibly corresponding to a propagation step. East of the ridge, the basement of the whole Iberia Abyssal Plain consists of highly thinned continental crust locally resting on a seismic reflector that resembles the S reflector previously recognized off Galicia. By analogy with the Galicia margin, we propose that the tilted crustal blocks lay on serpentinized peridotite derived from the upper mantle, the S reflector corresponding to the contact between crustal rocks and serpentinite.

  • 141. Ask, Maria
    et al.
    Janik, A.G
    Hood, J.A.
    Physical properties data at Hole 959D: comparison of core and log measurements and a proposed revision of lithologic units1998Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    A revised division of lithologic units is proposed for Hole 959D in the interval from 400 to 1000 meters below seafloor from Ocean Drilling Program Leg 159 based on combining the geophysical and sedimentological information. This new division is essential for further geological studies of the Cote d’Ivoire-Ghana Transform Margin area. A comparison is made between shipboard laboratory measurements made on core samples and in situ downhole logging data. Logging data, in conjunction with physical properties data, provide a more detailed record of the variation in the sediment column, which enables a more qualitative assessment of lithotype distribution. Emphasis is placed on distinguishing between the lithologic factors influencing the geophysical signals and artifacts resulting from imperfect data collection. Good overall agreement between core and log data for rotary core barrel cored sediments at Hole 959D is observed, and effects of core expansion caused by the removal of overburden pressure do not appear significant.

  • 142.
    Ask, Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Kopf, Achim
    DFG Research Center Ocean Margins, University of Bremen.
    Constraints on the state of in situ effective stress and the mechanical behavior of ODP Leg 186 claystones in the Japan Trench forearc2004Ingår i: Island Arc, ISSN 1038-4871, E-ISSN 1440-1738, Vol. 13, nr 1, s. 242-257Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Japan Trench forearc offshore Honshu Island in northeast Japan, where the 130-m.y.-old Pacific oceanic plate is presently subducted, was drilled during the Ocean Drilling Program Leg 186. Results from mechanical and sedimentological studies of claystones recovered from Sites 1150 and 1151 in the overlying erosional forearc wedge are reported in the present study. Although many physical properties are similar in the seismic (Site 1150) and aseismic portion (Site 1151) of the shallow forearc, Site 1150 displayed a higher abundance of open fractures, two prominent fault zones and enigmatic pore fluid signatures in the claystones. The abundance of weak mineral phases, together with high smectite contents (from X-ray diffraction), control the low friction coefficients of 0.33–0.39 of the claystones in ring-shear experiments. Results from triaxial testing proposed overall low magnitudes of in situ effective vertical stress, with somewhat lower values at Site 1150 than at Site 1151. Similarly, samples from Site 1150 displayed slightly higher pore fluid pressures than those at Site 1151. The high sediment porosities, which are in part also a result of intact diatom tests (from scanning electron microscope), together with the anomalous fluid signatures and elevated pore fluid pressures, could very likely result from upward migration and influx of deep-seated waters. Dewatering reactions at depth result in enhanced pore fluid pressure transients along out-of-sequence thrusts and consequently lower effective stress. At depths greater than that of Leg 186 drilling, elevated pressure–temperature conditions trigger mineral transformation and cementation, which result in increasing friction, unstable sliding and seismic rupture. Such earthquakes could have repeatedly disaggregated the consolidated claystone fabrics at the seismic site, and could be responsible for differences in yield strength and cementation when compared to the aseismic Site 1151.

  • 143. Ask, Maria
    et al.
    Leonard, J.N.
    Water content variations in lower trench slope sediment of Vanuatu, Nankai Trough, and Barbados Ridge: comparison of results from ODP Legs 110, 131, and 1341994Ingår i: Proceedings of the Ocean Drilling Program. Scientific results, College Station, TX, 1994, s. 531-547Kapitel i bok, del av antologi (Övrigt vetenskapligt)
  • 144.
    Ask, Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Morgan, Julia
    Rice University.
    Projection of mechanical properties from shallow to greater depths2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Deformation processes in sediments are directly controlled by the state of in situ effective stresses, the mechanical-, physical- and geochemical properties of the materials of the fault zone and surrounding wall rocks, and time. Measurements of these properties are needed for understanding of the process of earthquake generation. The recent drilling expeditions to Nankai Trough, by the Integrated Ocean Drilling Program demonstrate the technical difficulties involved in subduction zone drilling. At present, scientific drilling operations have successfully penetrated the decollement only at shallow depths in the Nankai accretionary prism. These data provide the only present access to future seismogenic zone materials. In the frontal region, the strata are being partitioned into accreting and subducting packages, some of which may ultimately pass into the seismogenic zone. Sediments deposited and locally cemented within the Shikoku Basin are partitioned by the basal decollement and they follow distinctive deformation pathways across the margin. Our hypothesis is that enhanced strength in the underthrust package allows it to carry excess pore fluids deep into the subduction zone, potentially to be released rapidly and seismogenically. The objectives for mechanical testing are to probe the yield and failure surfaces of these sediments, as well as their post-failure deformation behavior. This information is useful for making predictions about sediment response to accretion, underplating, and slip along the decollement. Reconsolidation tests have been carried out on Ocean Drilling Program cores collected from the reference site seaward of the active Nankai decollement zone off the southeast coast of Japan (ODP Site 1173). We have conducted two tests each from two subsamples from within Lower Shikoku Basin, approximately 30 m above, and approximately 85 m below the proto-decollement. This allows documentation of changes in mechanical strength and stress history across the proto-decollement horizon within the same lithostratigraphic unit. The initial porosities for the deeper and shallower samples are 43-44% and 56-57%, respectively. The results suggest that the shallower samples are significantly stiffer than the deeper ones, which is reflected by higher effective yield stress and higher elastic modulus in the shallower samples. The results regarding the elastic-plastic behavior is more challenging to interpret: One sample from above the decollement experienced brittle failure at an effective vertical stress of 8.7 MPa, whereas one sample from below the decollement show evidence on cement destruction and plastic deformation up to the maximum stress of 9.5 MPa. These two stress levels also are the highest effective vertical stress of samples. The results will contribute to our model for the evolution of deformation in sediments in the Nankai accretionary prism They will also allow us to project the mechanical behavior from shallow to greater depths.

  • 145.
    Ask, Maria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Morgan, Julia K.
    Rice University, Houston.
    Projection of mechanical properties from shallow to greater depths seaward of the Nankai accretionary prism2010Ingår i: Tectonophysics, ISSN 0040-1951, E-ISSN 1879-3266, Vol. 482, nr 1-4, s. 50-64Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Deformation processes in sediments at accretionary prisms are directly controlled by the state of in situ effective stresses, the mechanical, physical and geochemical properties of the materials of the fault zone and surrounding wall rocks, as well as time. Measurements of these properties and their evolution in space and time, are therefore needed for a full understanding of the process of earthquake generation within subduction zones.Reconsolidation tests have been carried out on Ocean Drilling Program cores collected from a reference site seaward of the active Nankai décollement zone off the southeast coast of Japan. The reconsolidation stress path subjects the samples to uniaxial strain deformation, which mimics their stress history, however at much higher loading rates than in the natural system. We have conducted two tests each from two mudstone samples within Lower Shikoku Basin. The samples were collected at 361 and 476 meter below seafloor, on either side of the protodécollement horizon.The objectives for mechanical testing are to probe the yield and failure surfaces of these shallow sediments (Considering their large scale behavior, our tests show that the samples collected above the protodécollement have higher strength than those below. We propose that cementation, microfabric and mineralogy of the sediments above the protodécollement result in a higher effective yield stress than predicted from in situ effective vertical stress at hydrostatic pore pressures. Sediments below the protodécollement, in contrast, are slightly underconsolidated, and provide an upper constraint on the magnitude of in situ effective vertical stress and pore-fluid pressure. We also used the test results to make initial predictions for the yield surface in 2D and 3D for subdécollement samples across the margin. The construction of the 2D yield surface is the first attempt to quantify the model of sediment deformation proposed by Morgan et al. (2007). These results hint that the presence of cement has a strong, and increasing, influence on sediment behavior. Further testing is needed to verify these findings.

  • 146. Ask, Maria
    et al.
    Müller, B.
    Stephansson, Ove
    In-situ stress determination from breakouts in the Tornquist Fan, Denmark1996Ingår i: Terra Nova, ISSN 0954-4879, E-ISSN 1365-3121, Vol. 8, nr 6, s. 575-584Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Tornquist Fan, a fan-shaped region in Denmark and Western Baltic, is situated in the transition zone between the Western and Northern European Stress Provinces. Breakout data from 20 wells (0.3-3.6 km) were analysed. The fan can be divided into three stress provinces: (i) The area south of the Romo Fracture Zone is part of the Western European Stress Province and has NNW-SSE orientation of the maximum horizontal stress, (ii) The sediment cover in the Norwegian-Danish Basin is dominated by ENE-WSW orientated maximum horizontal stress, (iii) The maximum horizontal stress is sub-parallel to the strike of the Sorgenfrei-Tornquist Zone. Deviations from the regional stress field were observed in wells close to faults and salt diapirs. In wells south of the Sorgenfrei-Tornquist Zone, breakout occurrence decreases with increasing age of the stratigraphic units. The downhole breakout distribution seems to correlate with lithology and thickness of the sediment layer.

  • 147. Ask, Maria
    et al.
    Stephansson, Ove
    Prediction of stress orientation and distribution in Denmark based on borehole breakout data from the Tornquist Fan and the Danish Central Graben1996Ingår i: Prediction and performance in rock mechanics and rock engineering: proceedings ; ISRM international symposium, Torino, Italy, 1996.09.2-5 / [ed] Giovanni Barla, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1996, s. 411-418Konferensbidrag (Refereegranskat)
  • 148. Asl, Aliakbar Golshani
    et al.
    Ahmadzadeh, Farzaneh
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Risk prioritization based on health, safety and environmental factors by using fuzzy FMEA2013Ingår i: Vol. 1, nr 4, s. 233-237Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Failure Mode and Effects Analysis is assessing technique which relies to the rule of preventing failure, which is used to identify potential hazards. This method is used with minimum risks to predict the problems and deficits in design stage or development of the processes and services in organizations. The methods main principal is based on multiplying three main parameters: severity, occurrence, detection. This method with all the advantages still has minor disadvantages that in this paper attempts has been made to eliminate these deficiencies by fuzzification. Results show that fuzzy FMEA will enables us to evaluate situations correctly and precisely.

  • 149.
    Asplund, Matthias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Wayside Condition Monitoring System for Railway Wheel Profiles: Applications and Performance Assessment2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The railway is an important mode of transport, due to its environmental friendliness, high safety level, and low energy consumption combined with a high transport capacity, among other factors. The Swedish railway network is old, there has been almost no expansion of the network during the past few decades, and more traffic is expected. Therefore, there is currently a demand for more track capacity and, in the short term, the existing network is expected to deliver the increased capacity. The railway operators in the network have a large impact on train delays, and wheel failures are one large contributor of delays. Delays destroy capacity and, therefore, capacityconsuming failures, such as abnormal wheels, need to be minimised. This can be achieved by using appropriate condition monitoring for the wheels on the track to find potential capacity consumers before failures happen. Therefore, the condition of the wheel-rail interface is important, since the state of the wheel influences that of the rail and vice versa. The monitoring of rail profiles is already being performed, but the monitoring of wheel profiles is still in the development phase. This thesis treats the applications and performance assessment of a wheel profile measurement system (WPMS), and presents case studies focusing on its system and measurement performance. The proposed applications concern how the information from the WPMS can be integrated with information from other data sources and with physical models to obtain a true current picture of the wheel behaviour. The thesis investigates the measurement performance of the WPMS by using a paired T-test and a number of quality measures, e.g. the reproducibility and repeatability, the precision-to-tolerance ratio and the signal-to-noise ratio. In conclusion, this thesis shows that the WPMS works well with an expected level of reliability in a harsh climate with respect to its measurement and system performance. By combining other data with the data from the WPMS, potentially abnormal wheels can be found in an early stage if the proposed new maintenance limit for the wheel parameter of the flange height is implemented. Furthermore, through adding a physical model to the process, the real contact condition of the actual wheel-rail interface can be evaluated and measurement deviations can be found. However, the wheel parameters, as well as the entire profile, need a high measurement quality with little variation, which seems to be an issue with respect to the measurement performance when advanced calculations are to be done. Therefore, a new approach for evaluating measurement performance has been developed using established statistical tools and quality measures with predefined acceptance limits; with the help of this approach, one can differentiate between the variation in the measurements originating in the different measurement units and the variation originating in the wheels. This new approach can be applied to judge the measurement performance of wheel profile condition-monitoring systems, and can also be implemented for other condition-monitoring systems to evaluate their measurement performance. Finally, this approach promotes the development of a condition-based maintenance policy by providing more reliable information for maintenance decision makers.

  • 150.
    Asplund, Matthias
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Drift, underhåll och akustik.
    Wayside Condition Monitoring Technologies for Railway Systems2014Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    The railway is an important mode of transport, due to its environmental friendliness, high safety level, and low energy consumption, among other reasons. Railways provide a sustainable means of transporting a large amount of freight and passengers, in a cost-effective and comfortable way. The railway system has a large number of stakeholders and a small improvement in the system will give many advantages, including financial savings and an increase in the quality of service. The Swedish railway network is old and there has been almost no expansion of the network during the past few decades. There is currently a demand for more track capacity and there are no more tracks availably at the network; therefore, the existing network is expected to deliver more capacity.The railway operators are the largest cause of train delays and wheel failures are one major contributor of the delays caused by operators. The infrastructure manager is the second largest owner of train delays, and a large contributor of their train delays is switches and crossings (S&Cs). This thesis shows proposals for how condition monitoring technology can be used more efficiently for both the infrastructure and the rolling stock to increase the reliability of their critical items by decreasing train delay. Firstly, the condition of the wheel-rail interface is important, in that a bad wheel influences the rail and vice versa. The monitoring of rail profiles is already in use, but the monitoring of wheel profiles is still in the development phase. This thesis shows the performance of a wheel profile measurement system (WPMS) for an extreme climate, and a case study of performance measures such as the accuracy and reliability of the system is presented. An additional topic dealt with is how the information from the WPMS can be combined with that from the wheel defect detectors to find early indications of wheels with bad behaviour. Secondly, the S&C is an essential component of a railway system in that it increases the flexibility by diverting traffic, but S&Cs need adequate support to work properly. A camera-monitoring method for S&Cs is presented which increases the inspection frequency and decreases the human activities on the track and the train delay. In conclusion, this thesis shows that the WPMS investigated works well with a high level of performance concerning measurement accuracy and reliability in an extreme climate, and that there is still some potential for improving the system. The combination of the WPMS and wheel defect detectors shows that wheels with a high flange height have a higher probability of ending up as wheels suffering from failures. A new maintenance limit for the flange height can reduce the number of wheel defects on the track. Camera-monitoring of the S&C will increase the availability and reliability of this item and even reduce the time on the track required for the maintenance action “check” through fewer inspections and maintenance actions. These proposed monitoring techniques can improve the railway system reliability by reducing the consequential train delay times, by decreasing the number of failures of wheels and S&Cs.

1234567 101 - 150 av 2313
RefereraExporteraLänk till träfflistan
Permanent länk
Referera
Referensformat
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Annat format
Fler format
Språk
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Annat språk
Fler språk
Utmatningsformat
  • html
  • text
  • asciidoc
  • rtf