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  • 201.
    Berglund, Andreas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Prognos av vägars bärförmåga vid tjällossningen: användning av temperatur som nyckeltal2010Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The global trend towards a warmer climate and temperatures near or just above 0 °C during winter months, will most likely be more common in future. One of the consequences of this climate change could, in a worst-case scenario, be freezing and thawing over a significant part of the winter with corresponding road bearing capacity problems. Bearing capacity problems may lead to increased costs to society when heavy traffic is forced to change route or carry less weight. In addition, road maintenance costs will increase. According to pulp industry calculations, this industry sector will face additional costs in the range of 510-590 Million SEK every year due to road bearing capacity problems. In addition to this, the costs related to the rapidly growing bio fuel industry will be added. If a reliable forecast of load-bearing capacity problems and potential load restrictions on roads can be found, it would be cost effective for road administration and society. This text presents the content of the licentiate work is presented and in what report more information could be found. One aspect of frost damage on roads that is highlighted in the thesis is decision making when conducting a road inventory. In a study conducted within the licentiate work it was shown that the results from different actors performing frost inventory on the same road stretch can vary a lot. There should be efforts made to reduce the individual dependence when performing a road inventory. The main part of the licentiate work deals with a model for the prediction of bearing capacity problems on roads. The work gives an idea of the possibility to use the temperature based model used in Minnesota, USA in Sweden. The evaluation is done by comparing falling weight deflectometer (FWD) test results with the results from the temperature based forecast model. When comparing the FWD results: AREA-parameter and subgrade modulus with results from the Minnesota model, the subgrade modulus seems to have the greatest agreement with the forecast model. However, they both seem to show the overall development of low bearing capacity during thaw. The overall conclusion about the temperature based forecast model is that it seems to give fairly good results and work well. It will work better if it can be further calibrated but it has some flaws if the temperature seesaws around 0 °C. The forecast model should, despite this, be able to assist road holders in Sweden as a planning tool, when dealing with bearing capacity problems during thaw.

  • 202.
    Berglund, Andreas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Studie av modell för prognos av vägars bärförmåga vid tjällossningen: "Minnesotamodellen"2010Rapport (Annet vitenskapelig)
    Abstract [en]

    Many roads are affected negatively by thaw with loss of bearing capacity as a consequence. Sometime load restriction policies must be applied on these roads. To be able to communicate potential bearing capacity problems in time with the road users, a prognosis model is needed. Such a model is described in this report. The model is described based upon a report made at Washington state department of transportation, WSDOT. WSDOT had carried out thermal analysis by FEM on four different road sections. The four sections are presented and the thermal properties of the road materials are given. A most likely misprint in the original report is commented upon and a table with correct SI-units is presented. The results coming from the thermal analysis is presented. Thawing in the tested road sections starts when the daily average air temperature is -1,7 °C to -1,1 °C. Limits for a should and a must level of accumulated thawing index is presented as 25 °F-days and 50 °F-days. When the level is reached load restrictions should apply. In the Minnesota Department of Transportation, Mn/DOT, version of the forecast model only one limit is used. The length of the load restrictions are based on the complete thaw of the road construction. Two equations for calculating the length of restrictions based on FI and TI are presented. Comparisons between the results of the forecast model and frost depth meters have been carried out and showed acceptable results. The forecast model is working better when fine grained materials is present than with coarse grained materials. The model was stated usable but in need of in-situ calibration. The model has been altered in the Mn/DOT version by letting the reference temperature vary during spring. This is said to be a way of taking the increasing intensity of the net heat flux and angle of the sun into consideration. It can also be seen as an easy way of calibrating the forecast model. The three day weather forecast is used to determine when the limit value for accumulated thaw index is reached. This gives the forecast model a three days forecast on bearing capacity problems. Within Mn/DOT maximum 8 weeks duration for load restrictions are used. Research showing that load restrictions are not socioeconomic defendable and that it is more economic to have the road repaired when it gets damaged is presented. Other works say that there is a value in load restrictions. Socioeconomic calculations may contain assumptions and whether or not they are correct is not discussed in this report. Before the forecast model could be implemented in Sweden there is a need for testing. Air and ground temperature data needs to be collected and analysed according to this report. The temperature data will give reference temperature and limit value to use when evaluating thaw index. The test results from the forecast model should be compared with for example falling weight deflection data from the same location to answer the question whether the agreement is good or not. The forecast model is straight forward and simple. Some questions about reliability need future testing before a recommendation whether or not it is suitable to be used in Sweden.

  • 203.
    Berglund, Andreas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Tjäle - en litteraturstudie med särskilt fokus på tjällossning2009Rapport (Annet vitenskapelig)
    Abstract [sv]

    Denna forskningsrapport är en litteraturgenomgång av en del av allt som finns skrivet om tjälprocessen och de problem tjälen skapar. Rapportens övergripande fokus ligger till en början på att ge en överblick över tjälprocessen och presentera grunderna i denna. Efter hand glider fokus över mot tjällossningen och de problem som förknippas med tjällossning. En allmän presentation av frusen jord, jord med en temperatur under 0°C, och en överblick över tjälforskningens historia från år 1765 och Beskow till mer nutida forskningsrön presenteras allra först i rapporten. Jordens termiska egenskaper är essentiell för tjälprocessen och beskrivs med hjälp av begrepp såsom termisk konduktivitet (värmeledningstalet λ), värmekapacitet (c), termisk diffusivitet (α) och latent värme (L). Temperaturprofilen beskrivs i termer av geotermisk gradient, whiplashkurva och aktivt område. Med aktivt område menas det område som tinar respektive fryser i permafrost och säsongstjäle.Tjälnedträngningen som orsakas av negativa varaktiga temperaturer vid markytan beskrivs i rapporten. Negativa yttemperaturer skapar ett värmeflöde från marken. Marken kyls ned i och med värmeavgången och bildandet av islinser i jorden inleds. Vattentransporten till tjälfronten som påverkar bildandet av islinser är komplex och fenomenet är än inte helt utrett. De två huvudspåren kapillärt sug och att vattentransporten beror av fysisk-kemiska egenskaper hos jorden presenteras. Vattentransporten till islinsen sker via en vattenfilm av ofruset vatten, den ofrusna vattenkvoten betecknas wu. Den hydrauliska konduktiviteten minskar med negativa temperaturer på grund av att vattentransporten sker i den ofrusna delen av vattnet, och wu minskar med negativa temperaturer. Beräkning av tjäldjup presenteras genom en härledning av Stefans formel, en presentation av Stefans modifierade formel och en förklaring av köldmängdsbegreppet. Modifierad Stefans formel som tar hänsyn till jordens värmekapacitet presenteras också. Förutom lufttemperaturen bestäms tjäldjupet i en jordprofil främst av jordmaterialets värmetekniska egenskaper. Tjällyftning och bestämning av tjällyftets storlek med segregation potential theory behandlas. Fenomenet vid tjällossning beskrivs samt problemen vid tjällossningen presenteras. För bärighetsproblem vid tjällossningen är dräneringen av vägkonstruktionen kritisk eftersom de ökade portrycken innebär minskade effektivspänningar och minskad skjuvhållfasthet. Dräneringsförmågan inverkar främst om urtjälningshastigheten är hög, mycket is övergår till vatten på kort tid. Sättningar på grund av tjällossning styrs främst av mängden is i jorden. Tjälfarlighetsklassificeringssystemen använda i Sverige, Norge, Finland och USA beskrivs och en jämförelse mellan dessa görs. Två jordar klassificeras utifrån kornfördelningskurvorna, för en grusig sand ger ländernas system samma svar, ej tjälfarlig. Även för den andra jorden, en sandig siltig lermorän klassificeras jorden som tjälfarlig, dock i olika grad. Hur vägar påverkas av tjälnedtränging (höjd hållfasthet, lägre hydraulisk konduktivitet), tjällyftning och tjällossning (bärighetsminskning, tjälskott med mera) beskrivs. Vägverkets system för väderdata VViS presenteras. Med hjälp av väderdata kan modeller för införandet av lastrestriktioner skapas. CTI-fordon har fördelar vid bärighetsnedsättningar. Sverige använder enbart visuella observationer vid införandet av lastrestriktioner på grund av bärighetsnedsättningar vid tjällossning. Flera andra länder och stater i USA använder mer sofistikerade metoder. I Minnesota används väderdata i form av frys- (FI) och töindex (TI) tillsammans med en referenstemperatur för att förutse när lastrestriktioner bör införas. Kanske är "Minnesotamodellen" något för Sverige.

  • 204.
    Berglund, Andreas
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Tjälinventeringsprojektet: en jämförande studie av tjälinventeringar gjorda av olika aktörer2010Rapport (Annet vitenskapelig)
    Abstract [en]

    Roads are affected by frost. For maintenance and action planning of these roads, a well performed inventory is a necessary base. It will also be a base for priority of different objects for repair and maintenance. Therefore, it is very important to have a similar ground for the judgment. This can be difficult to achieve as different companies and persons are enrolled different years due to type of contract used, capacity, experience, knowledge etc. In a pre-study great differences were found when comparing two inventories done on the same road in year 2008 and 2009. The question was then raised, if the provided information on how to perform an inventory was good enough in order to carry out a high quality work. Another question raised, was if the differences really are that obvious between different persons performing the inventory.The method used for the study was to have four actors to carry out an inventory each on the same road, at the same time, and then compare the obtained results. The actors were "Konsult A" and B, Swedish Transport Association (TV) and persons from Luleå University of Technology (LTU). Ranked in order of practical experience the most experienced was Konsult B, then Konsult A, TV and LTU. The road studied was AC805 Lidbacken to Femvägaskälet. It is situated outside Skellefteå in the county of Västerbotten in the north part of Sweden. The total length of the studied road was about 15 km and it has an ADT of 576. Four sections, which represented the road as a whole and also showed the main differences and similarities, were closer analyzed. One section focused on an overview, one on cracks and two sections focused on bumps and roughness. In the report, the results from the four inventories are presented graphically in order to give the reader an overview and a chance to comparison. The results show that there are both great differences and similarities between the four inventories. The two most experienced, Konsult A and Konsult B had about the same percentage of their total crack length in class 2 (66 respectively 60%) and class 3 (~30%). The total amount of inventoried crack length differs however. Konsult A have in total 7355m and Konsult B 9157m, which means that Konsult A only reports approximately 80% of the length reported by Konsult B. TV had 18% class 2 and 82% class 3 cracks with a total length of cracks being 3246m, while LTU had 38% class 2 and 24% class 3 cracks. In this case the total crack length was reported to be 11029m. This means, that the total length of reported cracks varies between 3246 m to 11029 m, corresponding to approx. 21% and 74% of the total road length.The most experienced (Konsult B) and the least experienced performer (LTU) show most similarities in the overall road condition assessment and placement of damages. It is mentally exhausting to perform a road inventory by hand without small amount of technical support. It is shown in the report that the resolution seems to decrease after some time of work. As a consequence, many cracks in class 1 are registered in the beginning of the studied road stretch, while in the end cracks are more registered as long single cracks. After some time of work more cracks are registered as coherent cracks while they in fact are single cracks. It should therefore be considered if technical supporting systems, like e.g. GPS and computers with well developed software, should be more used in order to increase efficiency and quality of the final work. This should also reduce the impact of subjective decisions.One observation done in the study is that different persons might have different views of the purpose of the road inventory. One view is to perform just a road inventory, without any specific purpose, more than to get a view of the quality of the road. Another point of view is to do an inventory with the focus of what type of actions are to be carried out in future in mind. Depending on the focus, the results seem to differ. In this study, it seems like LTU, Konsult A and Konsult B have performed the inventory in the first way, while TV seems to have carried the inventory out with future actions in mind. This conclusion is based upon the observation that TV did not note any damages in class 1 throughout the whole road stretch, while the other did. By analysing the inventory results, it was found that errors in the distance measurements were present. It is therefore proposed that the customer should consider GPS-length measurements to eliminate this source of error. Inventory done with the base of digital photos will minimize some of the length measurement problems if the photos are taken by a camera connected to a GPS. However, inventory done by using digital photos only have several disadvantages in comparison with ordinary field inventory. The major drawback of this methodology is the difficulty to discover small damages and roughness. It is difficult to classify roughness. The roughness effect on driving experience is very much dependent on the speed of the inventory vehicle. Based on this study the speed of the inventory vehicle needs to be considered when doing a roughness inventory. Roughness inventory should be done at the roads intended speed to ensure that the roughness impact on driving comfort is correctly experienced and registered. One way to enhance the quality of road inventory could be to develop a clear and easy to understand description of method. It should be emphasised that experience is a key component when doing road a inventory, but an increased use of technical support systems can reduce the scatter in the assessment.

  • 205.
    Berglund, Andreas
    et al.
    LTU.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Comparison between temperature based thaw weakening prediction model and field observation methods2011Inngår i: Proceedings of the 21st International Conference on Port and Ocean Engineering under Arctic Conditions, Montreal, 2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Structures like roads and port yards located in cold climate are affected by freezing and thawing every year. The global trend of a warmer climate and temperatures around 0°C for longer periods of time will change the freezing/thawing behaviour in many locations. The tendency will changeto have several freezing /thawing cycles in a given location every year. The bearing capacity of low volume roads and simple port yards will be affected by a prolonged thawing period with lower bearing capacity as a consequence. Bearing capacity problems can lead to increased costs for traffic as well as increased maintenance costs. Due to very high costs for destroyed structuresduring thaw, a lot can be gained if bearing capacity problems at a given site can be forecasted well in advance in order not to destroy the structure. Such a method should preferably be based upon simple measurements like air temperatures to make it easy to use also in remote areas. In the described temperature based model air and ground temperatures are used to develop anaccumulated thaw index and corresponding limits. When the thaw index limit is reached, the construction at the evaluated depth thaws, leading to increased pore water pressure and reduction of strength and bearing capacity. This paper presents a study of the application of the model at low volume roads in Sweden. Bearing capacity at the road was evaluated from field tests by falling weight deflectometer (FWD) test carried out 24 times during the thawing season i.e.March 4 through June 9. Predictions made by the model were compared with the subgrade module evaluated from the FWD series. The results show that the model might be possible to use in Sweden and elsewhere if minor adjustments are carried out.

  • 206.
    Bergman, Stina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Arkitektur och vatten.
    Livscykelanalys för grundläggning av byggnader: Användningen idag och hur metoden kan tillämpas i praktiken2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [sv]

    Byggsektorn står idag för en stor andel av växthusgasutsläppen vid produktion av byggmaterial ochanvändningen av byggmaskiner under byggproduktionsskedet. Det nationella målet är att Sverige år 2045ska vara koldioxidneutralt och utifrån detta mål har Fossilfritt Sverige, tillsammans med ett stort antalaktörer från bygg- och anläggningssektorn, tagit fram en färdplan för hur branschen ska bli klimatneutralt.Grundläggning står för en betydande del av den totala byggnadens klimatpåverkan och för att nå måletmed ett klimatneutralt Sverige år 2045 är det viktigt att discipliner inom grundläggning börja arbeta medutveckling och optimering av grundläggningskonstruktioner för att minska klimatpåverkan.

    I detta examensarbete har en intervjustudie utförts för att kartlägga vilka aspekter som styr valet avgrundläggningsmetod idag utifrån entreprenören och konsultens perspektiv samt för att kartlägga hurdessa aktörer använder livscykelanalys inom grundläggning av byggnader. En fallstudie har utförts för attundersöka hur livscykelanalys kan användas för att beräkna och jämföra klimatpåverkan samtprimärenergianvändningen från grundläggningsmetoder för byggnader genom att prova och utvärderatvå digitala LCA-verktyg.

    En litteraturstudie har genomförts för att skapa kunskap inom grundläggning och för att skapa förståelseom klimatpåverkan från byggsektorn samt vilka klimatkrav som finns. Litteraturstudien har legat till grundför valet av de två digitala LCA-verktyg som används i fallstudien samt har används för att ta fram enintervjuguide. Intervjuer har genomförts med aktörer från konsult- och entreprenadföretag som harvarierande erfarenheter och kunskaper inom livscykelanalys för grundläggning. Vidare har en fallstudiegenomförts där en jämförande livscykelanalys utförs mellan två grundläggningsmetoder, platta med pålaroch platta med lastkompensation, genom att använda två digitala LCA-verktyg, Klimatkalkyl 6.0 och BM1.0. LCA-studien utgår från verktygens avgränsningar och beaktar endast första delen av livscykeln,byggskedet (modul A1-A5) där Klimatkalkyl 6.0 beräknar klimatpåverkan och primärenergianvändningenoch BM 1.0 beräknar endast klimatpåverkan.

    Resultatet från intervjuerna visar att grundläggningsmetoder ofta väljs utifrån den ekonomiska aspektenmen att personlig erfarenhet, geografisk och historisk tradition även påverkar. Respondenterna anser attklimat- och miljökrav som förekommer i projekt ofta är otydliga och svåra att förstå. Intervjustudienindikerar att användningen av livscykelanalys är begränsad. Enligt respondenterna skulle användningenöka om man utvecklade kompetens hos konsulter och entreprenörer, förenklade LCA-modellen menframförallt om deras beställare tydliggjorde kravställningarna.

    I fallstudien visar de två verktygen på olika klimatpåverkan för respektive grundläggningsmetod och olikaskillnader vid jämförandet av de två grundläggningsmetoderna. Båda verktygen visar att grundläggningmed platta med pålar ger en lägre klimatpåverkan än platta med lastkompensation under byggskedetmed givna förutsättningar. Skillnaden mellan grundläggningsmetoderna är 2 eller 5 tonkoldioxidekvivalenter beroende på vilket verktyg man använder, vilket motsvarar cirka 13 respektive 23procent i skillnad. Båda verktygen visar även att betong, cellplast och stål är de byggnadskomponentersom bär den största andelen av den totala klimatpåverkan för respektive grundläggningsmetod.

    Ingen av verktygen Klimatkalkyl 6.0 och BM 1.0 är utvecklade för grundläggning av byggnader och i bådaverktygen saknas det byggnadsdelar som ingår i grundläggningsmetoderna, som studeras i fallstudien.Resultatredovisningen från respektive verktyg är även svårtolkade och bör utvecklas. Trots detta så ansesdet att båda verktygen kan användas som hjälpmedel för att beräkna och visa vilketgrundläggningsalternativ som ger minst klimatpåverkan.

    Då den ekonomiska faktorn idag är styrande för valet av grundläggningsmetod kan denna parameteranvändas som styrmedel för att öka arbetet med klimatanpassade lösningar. Förslag på fortsatta studierär att ta fram en relation mellan kostnader och klimatpåverkan för grundläggningsmetoder samt attundersöka hur man kan implementera livscykelanalys på projektörsnivå för att öka dess användning.

  • 207.
    Bernander, Stig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Analys av progressiva skred utförda av Con-Geo: Bilaga till Skredet i Småröd, Rapport 1 - Skredorsak2007Rapport (Annet vitenskapelig)
  • 208.
    Bernander, Stig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Angående Statens Geotekniska Instituts Rapport Nr 18: "Un élefphant naît une souris"1983Inngår i: Geotekniknytt (och lite gammalt), Vol. 1983, nr 1, s. 1-17Artikkel i tidsskrift (Annet vitenskapelig)
  • 209.
    Bernander, Stig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Down-hill progressive landslides in soft clays: Triggering disturbance agents, Slide Propagation over horizontal or gently sloping ground, Sensitivity related to geometry2008Rapport (Annet vitenskapelig)
    Abstract [en]

    A numerical model is presented and discussed for down-hill progressive landslides in soft clays. A simple-to-use spread sheet is given and used in order to illustrate the influence of the sensitivity of the clay and the geometry of the ground. The model is also used to discuss the agents and the mechanisms that formed the large landslide in Surte at the Göta River in 1950.

  • 210.
    Bernander, Stig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Lerors hållfasthet och deformationsegenskaper i konstruktioner där leran icke ugör den enda stabiliserande komponenenten1975Inngår i: NGM 75: Nordisk Geoteknikermöde i Köbenhavn 22-24.5.1975, Köbenhavn: Polyteknisk Boghandel og Forlag, 1975, s. 155-172Konferansepaper (Fagfellevurdert)
  • 211.
    Bernander, Stig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Progressive landslides in long natural slopes: Formation, potential extension and configuration of finished slides in strain-softening soils2011Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    After the large landslide in Tuve (Gothenburg, 1977), the author began developing a finite difference model for slope stability analysis taking the deformation-softening of soft sensitive clays into consideration. In the model, the mean down-slope deformation in each element caused by normal forces is maintained compatible with the deformation generated by shear stresses. He developed software for the model and presented it at international soil mechanics conferences during the 1980-ies. In 2000 he summarized his findings in a Licentiate thesis. An easy-to-use spread-sheet has also been developed. In this thesis the author conveys his experiences of slide modeling focusing on the nature of triggering agents and the different phases that a slope may undergo before its stability becomes truly critical.

  • 212.
    Bernander, Stig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Progressive landslides in long natural slopes: potential extension and configuration of finished slides in strain-softening soils2000Licentiatavhandling, monografi (Annet vitenskapelig)
    Abstract [en]

    A finite difference method is presented for progressive slides in long natural slopes. The method is based on a strain softening material model. A detailed worked out example is given as well as examples using a spread sheet PC program and a PC program for Windows. Several Scandinavian slides are analysed and discussed as case studies e g Tuve (1977), Surte (1951), Bekkelaget (1953), Rollsbo (1967), Rävekärr (1971), Tre-styckevattnet (1990) and Svärtaån (1938). The nature of down-slope progressive failures in natural slopes is described and the applicability of ideal-plastic failure analysis is questioned. Principles and procedures for investigation potential landslides are presented. A short historical background to the landslide problem is given in an introductory chapter.

  • 213.
    Bernander, Stig
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Relationship between the appearence of a finished landslide and the mechanisms acting during the slide1984Inngår i: NGM-84, Nordiskt Geoteknikermöte 1984 i Linköping, Linköping: Statens geotekniska institut (SGI) , 1984, s. 409-416Konferansepaper (Fagfellevurdert)
  • 214.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Dury, Robin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Laue, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Progressive Landslide Analysis in Canadian Glacial Silty Clay in Churchill River2017Inngår i: / [ed] Vikas Thakur, Jean-Sébastien L’Heureux, Ariane Locat, 2017, s. 1-Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    The poster presents the risks for a progressive landslide in a natural dam. The stability will be critical when the water level is raised after the building of a hydro power plant, Bernander (2016), Dury (2017). The analysis is based on a finite difference method developed by Stig Bernander (2011), Bernander et al.(2016)

     

    The following issues will be discussed:  

    - Material properties

    - Risk for liquefaction

    - Three possible failure surfaces: one horizontal, one inclined and one curved

    - Failure riska for different material propeties

    - The need to check the real properties of the soil

  • 215.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Gustås, Hans
    Skanska.
    Olofsson, Jan
    Skanska.
    Improved model for progressive failure analysis of slope stability1989Inngår i: Proceedings of the twelfth International Conference on Soil Mechanics and Foundation Engineering, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1989, Vol. 21/3, s. 1539-1542Konferansepaper (Fagfellevurdert)
  • 216.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Gustås, Hasse
    Skanska.
    Consideration of in sity stresses in clay slopes with special reference to progressive failure analysis1984Inngår i: Canadian case histories: landslides: Preprint volume for the 37. Canadian Geotechnical Conference organized jointly with the 4. International Symposium on Landslides, Totonto: Univ. Toronto Press , 1984Konferansepaper (Fagfellevurdert)
  • 217.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Gustås, Hasse
    Skanska.
    Dynamisk studie av ett progressivt brott i en naturlig slänt1984Inngår i: NGM-84, Linköping: Statens geotekniska institut (SGI) , 1984, s. 431-442Konferansepaper (Fagfellevurdert)
  • 218.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Kullingsjö, Anders
    Skanska Teknik, Göteborg, Chalmers University of Technology.
    Gylland, Anders K
    Multiconsult, Norwegian University of Science and Technology (NTNU), Trondheim.
    Bengtsson, Per-Evert
    Statens Geotekniska Institut, Linköping, PEB Geoteknik.
    Pusch, Roland
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Olofsson, Jan
    Skanska Sverige AB, Skanska Teknik, Göteborg.
    Elfgren, Lennart
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Downhill Progressive Landslides in Long Natural Slopes: Triggering Agents and Landslide Phases modeled with a Finite Difference Method2016Inngår i: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 53, nr 10, s. 1565-1582Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A large landslide in Tuve (Gothenburg, Sweden 1977) initiated the development of a model for slope stability analysis taking the deformation-softening of soft sensitive clays into consideration. The model studies triggering agents and five phases in progressive slope failure are identified: (1) in-situ, (2) disturbance, (3) unstable ‘dynamic’, (4) transitory (or permanent) equilibrium, and (5) ‘global’ failure. The clay resistance in these phases may differ widely; mostly due to different rates of loading. Two time dependent failure criteria are defined: (i) the triggering load condition in the disturbance Phase (2), and (ii) the transitory equilibrium in Phase (4), indicating whether minor downhill displacements or a veritable landslide catastrophe will occur. The analysis explains why downhill landslides tend to spread over vast areas of almost horizontal ground further down-slope. The model has been applied to landslides in Scandinavia and Canada. Three case studies are briefly discussed. The model is a finite difference approach, where local downhill deformations caused by normal forces is maintained compatible with deviatory shear deformations above the potential (or the established) failure surface. Software and an easy-to-use spreadsheet are introduced as well as recent developments. See also Video Abstract.

  • 219.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Olofsson, Ingvar
    Skanska.
    On Formation of Progressive Failures in Slopes1981Inngår i: Proceedings of the Tenth International Conference on Soil Mechanics and Foundation Engineering, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1981, Vol. 3, s. 357-362Konferansepaper (Fagfellevurdert)
  • 220.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Svensk, Ingvar
    Skanska.
    On the Brittleness of Soft Clays and its Effects on Slope stability1982Inngår i: Väg- och Vattenbyggaren, ISSN 0042-2177, nr 7-8Artikkel i tidsskrift (Annet (populærvitenskap, debatt, mm))
  • 221.
    Bernander, Stig
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och -produktion.
    Svensk, Ingvar
    Skanska.
    Holmberg, Gunnar
    Skanska.
    Bernander, Jarl
    Skanska.
    Isacsson, K
    Skanska.
    Shear strength and deformation properties of clays in direct shear tests at high strain rates1985Inngår i: Proceedings of the eleventh International Conference on Soil Mechanics and Foundation Engineering, Rotterdam: Balkema Publishers, A.A. / Taylor & Francis The Netherlands , 1985, Vol. 2/B/5, s. 987-990Konferansepaper (Fagfellevurdert)
  • 222.
    Bey-Gress, Ch.
    et al.
    École nationale supérieure des arts et industries de Strasbourg.
    Laue, Jan
    Institut für Geotechnik, ETH Zürich.
    Seiffert, J-G
    École nationale supérieure des arts et industries de Strasbourg.
    Modélisation de l'interaction sol-fondations superficielles1999Inngår i: Revue Francaise de Geotechnique, ISSN 0181-0529, Vol. 88, nr 3, s. 37-45Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Les ouvrages de génie civil sont classiquementdimensionnés selon les sollicitations qu'ils doiventreprendre, avec des conditions limites locales souventpeu réalistes. Les fondations sont dimensionnées parailleurs, selon les sollicitations transmises, mais en aucuncas la modification du comportement de l'une des partiesn'est prise en compte pour le dimensionnement de l'autrepartie. Il est nécessaire de comprendre d'abord ce qui sepasse au niveau local sol-fondation pour caractériser lecomportement de cet ensemble de propriétés mécaniqueset rhéologiques différentes soumis à des sollicitationscomplexes, avec tous les problèmes inhérents au contact.Le travail présenté concerne des fondations superficiellesposées sur un milieu pulvérulent homogène isotrope,sous des sollicitations de type effort vertical et momentcouplé ou non-couplé.Modelisation

  • 223.
    Bhanbhro, Riaz
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mechanical Behavior of Tailings: Laboratory Tests from a Swedish Tailings Dam2017Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Tailings is leftover material from mining industry and is produced in huge quantities approximately 70-99% of the ore production.  Tailings material is stored as impoundments by constructing tailings dams which are often constructed with tailings material itself. Tailings are artificial material and the mechanical behavior of tailings material upon loading is different as compared to natural soil materials. There are number of dam failures reported every year which has severe impact on inhabitants and environment nearby. Considering the failures of tailings dams and consequences there is a need to understand the tailings material in depth for safe existence of these dams. The confident dam design can assure the safe existence of tailings dams for long term as these dams are presumed to function for generations to come. The material properties in tailings dams can change during operation due to raising of new layer. Raised new layer can change stress level, which in turn may change the material properties in terms of strength, pore pressures, grain sizes etc. Today mostly tailings dam are designed by performing analysis for safety for existing and future rasings as well. These analyses are based upon a for certain factor of safety. Not very much can be done with design and analysis for tailings material if the material is not described very well. Understanding of tailings material in depth can provide help for detailed material parameters which later can be used in safety assessment for future raising and changed conditions in dam.

    This study presents the work carried out on tailings material from a Swedish tailings dam. The study is conducted on undisturbed and disturbed tailings material. The undisturbed tests are carried out to understand material properties as per in-situ conditions. Whereas disturbed materials are used to created different materials with different particles sizes. Initially in this study the basic properties of tailings materials are studied e.g. specific gravity, phase relationships, particle sizes, particle shapes and shear behavior on collected samples at various depths. During direct shear tests, the unexpected vertical height reductions were observed, these results are presented in this study. The comparison of strength parameters by direct shear and triaxial tests on material from various depths is also done and presented.

    Based on results from direct shear, triaxial and oedometer tests on uniform sized tailings material; the evaluation of primary and secondary deformations and particle breakage and effect of vertical loads is also carried out and presented. The study also includes the comparison of strength parameters for each particles size. The breakage of particles is analyzed by sieving the material after direct shear tests followed by a particle shape study. The effect of deposition on shear strength parameters is also studied by construction of samples with different angle of deposition of material. The strength parameters of uniform sized particles in triaxial tests are also evaluated and discussed.

  • 224.
    Bhanbhro, Riaz
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mechanical Properties of Tailings: Basic Description of a Tailings Material from Sweden2014Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Tailings dams are constructed to store waste material from mining industry and usually these dams are raised with time depending upon production rate. Tailings material is sometimes used in construction of tailings dams. Tailings are artificial material and the behavior of tailings material upon loading is different compared to natural soil materials. The mechanical properties of tailings have influence on the performance of a tailing dam. Since the tailings dams are constructed to withstand for long times, it is essential to understand tailings materials in depth in order to assure safe existence of the dams in short term as well as in long term perspective. This licentiate thesis describes the present work carried out on sulphide rich tailings from one mine in Sweden. The material presented is based upon material from three different papers. The first paper describes the basic characteristics of tailings which includes; specific gravity, phase relationships, particle size, particle shape and direct shear behavior. The second paper discusses direct shear tests carried out on tailings from one Swedish mine. Shear strength parameters are evaluated and results from 27 tests (15 drained and 12 undrained tests) are discussed. This paper also describes the vertical height reductions observed during direct shear tests. The third paper focuses on the laboratory results from triaxial tests conducted on tailings materials. This paper shows the drained behavior of tailings under application of different consolidation pressures.The results from particle analysis showed that smaller particles were very angular and bigger particles were sub angular. The material was classified as silt and silty sand. The average particle density (ρs) is 2.83t/m3. The dry density and void ratios were found to be 1.18–1.65 t/m3 and 0.72–1.41 respectively. During direct shear tests vertical height reductions were observed with slight increment in pore pressures. The strain hardening behavior was observed in both drained and undrained conditions in direct shear tests. The strength parameters determined in triaxial test were higher than of those calculated in direct shear tests. Friction angle ϕ' in triaxial tests were found to be 39 to 41degrees and it did not showed any effect with relation to depth. The cohesion and friction angle in direct shear test at 0.15radian, in drained tests were found as in range of 9.7-33.7kPa and 12.5-18.3 degrees respectively. The same parameters for undrained tests were found as 7.1-16.1 kPa and 16.0-20.4 degrees for cohesion and friction angle respectively.

  • 225.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Frequent breaches in irrigation canals in Sindh Pakistan2014Inngår i: Journal of Water Resource and Protection, ISSN 1945-3094, E-ISSN 1945-3108, Vol. 6, nr 4, s. 214-223Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Every year a number of breach failures occur in Irrigation Canals in Sindh. Those failures cause displacement of thou-sands of people, destruction of properties, land, and damages costly crops worth millions rupees. In addition to that breach failures are also can cause water shortages when failure occurs during peak demand period. There are various causes of embankment failures that include overtopping, internal erosion, structural defects and piping. State of art for breach failures is presented in this paper and suggestions for prediction of breaches in context to canals in Sindh are discussed. Seepage and slope stability analyses are recommended for long term breach predictions.

  • 226.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Effect of Particle Size On Mechanical Properties and Particle Breakage of Tailings2017Inngår i: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tailings material can have different material properties depending upon the type of ore and ore refining process and particle size distribution. Tailings dams are constructed as walk away solutions. Staged construction of tailings dams may lead to breakage of particles in subsequent layers resulting in change in particle sizes of material. This may lead to change in strength parameters upon change in particle sizes. This paper presents the direct shear tests performed on tailings material from a tailings dam. Remolded samples were manufactured in laboratory. The tailings material is separated in to four different particle sizes i.e.1-0.5mm, 0.5-0.25mm, 0.25-0.125mm and 0.125-0.063mm. The tests are performed on different normal stress levels as 50, 100, 150, 300 and 500kPa.The strength parameters are evaluated for each particle size and compared with said particle sizes. In order to study the effect of deposition, the tests are also performed on same material deposited in vertical and horizontal direction. This paper also describes the study of breakage of particles during direct shear tests by sieving the material at the end of each test. 

  • 227.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mechanical Behavior of Uniformed Tailings Material in Triaxial Tests2017Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 22, nr 06, s. 1717-1730Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tailings dams are raised with time depending upon rate of generation of waste. A tailings dam can contain different particle sized materials within its dam body. The newly raised embankment in a tailings dam can be considered as vertical load being applied on subsequent layer. The applied loads can cause deformations and breakage of particles. The particle breakage can then lead to a skeleton with new particle size particles and hence can lead to new material properties. This paper provides the results from triaxial tests conducted on uniformed particle sizes as, 0.5mm-0.25mm, 0.25mm-0.125mm and 0.125mm-0.063mm.  The tests are performed at various effective radial stresses. The results are evaluated and compared with each particle size. The results include stress-strain and volumetric behavior during shearing, the effective stress ratio and stress-dilatancy plot. The friction angles are also evaluated and compared with different particle sized specimens. It was found that effective stress ratios were slightly higher when tests were performed at lower confining stresses and vice versa. It was also observed that particle size did not show any effect of friction angles.

  • 228.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mechanical Properties of Soft Tailings from a Swedish Tailings Impoundment: Results from Direct Shear Tests2014Inngår i: The Electronic journal of geotechnical engineering, ISSN 1089-3032, E-ISSN 1089-3032, Vol. 19, nr Z, s. 9023-9039Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The shear strength of tailings can vary depending upon the type of ore and method of construction. Tailings dams may possess loose layers in subsequent layers, which may have low shear strength. Since the tailings dams are made-up to last for longer times, the strength parameters and material behaviors are essential to understand, especially potential for static liquefaction in loose layers. This article presents the results from direct shear tests performed on samples from loose layer of a tailings dam. Both drained and undrained tests are carried out. The results indicated the strain hardening behavior in tailings material which indicates loose condition. The shear strength was found to be relatively low as compared to typical values of tailings in literature. A contractant volume behavior was observed for all the tests. During shear tests the vertical height reductions in samples were observed. These changes were significantly increased after peak shear followed by slight increment in pore pressure along shearing angle. The reasons for these height changes are not fully known, but may be a rearrangement in skeleton or breakage of particles during shear which needs further investigative studies.

  • 229.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Mechanical Properties of Soft Tailings from different Depths of a Swedish Tailings Dam: Results from Triaxial tests2018Inngår i: Scientia Iranica. International Journal of Science and Technology, ISSN 1026-3098, E-ISSN 2345-3605, Vol. 25, nr 1Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Construction of tailings dams is done in stages by raising it layer by layer depending on production rate of a mine. These layered dams may possess different strengths and materials properties in each layer i.e. strength parameters, behavior with loading. Tailings dams may have loose layers in subsequent layers, which upon further loading may be susceptible to stability issues. Identification of material properties and behavior is important to know for safety of dam with further raising and long term perspective modeling. This paper presents the results from drained Triaxial compression tests conducted on samples collected from loose layers, from different vertical depths of a tailings dam. The results indicated that depth did not show much influence on strength parameters determined by drained triaxial tests. The different confining pressures influenced the strain-stress behavior, high confining pressures stress-strain curve showed tendency to formulate straighten line of stress-strain curve, with contractant volume behavior along axial strains. The influence of void ratio on effective stress ratio was observed.

  • 230.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rodriguez, Juan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Basic description of tailings from Aitik focusing on mechanical behavior2013Inngår i: International Journal of Emerging Technology and Advanced Engineering, ISSN 2250-2459, E-ISSN 2250-2459, Vol. 3, nr 12, s. 65-69Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tailings are artificial granular materials that behave different as compared to natural soil of equal grain sizes. Tailings particle sizes, shapes, gradation and mechanical behavior may influence the performance of tailings dams. Hence it is essential to understand the tailings materials in depth. This article describes present studies being carried out on Aitik tailings. Basic tailings characteristics including specific gravity, phase relationships, particle sizes, particle shapes and direct shear behavior are presented in this article. The results showed that particles size decreases along depth from surface for collected sample locations. The angularity of the particles increases as the grain size decreases. Vertical height reduction was observed during shearing of samples by direct shear tests.

  • 231.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Memon, Irfanullah
    Quaid-e-Awam University of Engineering Science and Technology, Nawabshah.
    Ansari, Aziz
    Quaid-e-Awam University of Engineering Science and Technology, Nawabshah.
    Shah, Ahsan
    Quaid-e-Awam University of Engineering Science and Technology, Nawabshah.
    Memon, Bashir Ahmed
    Quaid-e-Awam University of Engineering Science and Technology, Nawabshah.
    Properties Evaluation of Concrete using Local Used Bricks as Coarse Aggregate2014Inngår i: Engineering, ISSN 1947-3931, E-ISSN 1947-394X, Vol. 6, nr 5, s. 211-216Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With time concrete / reinforced concrete has become the popular material for construction. Modern industry utilizes this material a lot and has produced various beautiful, eye catching and amazing structures. Due to modern requirements for living and developed construction industries, the old buildings (usually constructed with brick masonry) are demolished and are replaced with new modern buildings. Demolition of buildings results in waste materials which can create waste related problems and environmental issues. By using recycled aggregates weight of concrete can also be reduced, which can also solve problems related to self-weight of concrete. In this paper attempt has been made to use local used bricks from vicinity of Nawabshah, Pakistan, as coarse aggregate. Concrete cubes made with local recycled bricks are cast and tested for overall weight of concrete, moisture content, dynamic modulus of elasticity and compressive strength (nondestructive and destructive methods). The results showed that concrete derived from recycled aggregates attained lower strength than regular concrete. More detailed elaborated work is recommended with different mix ratios and different proportions recycled aggregates for better conclusions.

  • 232.
    Bhanbhro, Riaz
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Rodriguez, Juan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Evaluation Of Primary And Secondary Deformations and Particle Breakage of Tailings2015Inngår i: From Fundamentals to Applications in Geotechnics: Proceedings of the 15th Pan-American Conference on Soil Mechanics and Geotechnical Engineering, 15–18 November 2015, Buenos Aires, Argentina / [ed] Diego Manzanal; Alejo O. Sfriso, IOS Press, 2015, s. 2481-2488Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Tailings are the waste product of mining which is left over after extraction of materials of interest. Tailings material may possess different material properties depending upon type of ore and method of concentration. Sometimes the tailings material itself is used in construction of tailings dams and tailings dams are constructed to withstand for long times. A tailing dam can be exposed to settlements due to incremental load as these dams are raised in stages. Increasing load with time may also lead to particle breakage. This article presents the results from oedometer tests conducted on tailings materials. The study includes the stress-deformation behavior and particle breakage of tailings material of different gradations upon application of incremental loads in oedometer tests. The samples were collected from different sections of tailings dam from Sweden. Remolded samples were manufactured in laboratory as four batches of particle sizes i.e. 1-0.5 mm, 0.5-0.25mm, 0.25-0.125mm and 0.125-0.063mm. The results are analyzed from tested samples at different stress levels and compared with different particle sizes. The breakage of particles of each batch is analyzed by sieving the specimens after oedometer tests. The results are evaluated in terms of primary and secondary deformations. The primary and secondary deformations are also compared with different particle sized specimens.

  • 233.
    Billstein, Mats
    et al.
    Luleå tekniska universitet.
    Svensson, Urban
    Luleå tekniska universitet.
    Johansson, Nils
    Luleå tekniska universitet.
    Application and validation of a numerical model of flow through embankment dams with fractures: Comparisons with experimental data1999Inngår i: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 36, nr 4, s. 651-659Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The focus of this paper is on the development and validation of a numerical model of flow through simplified embankment dams with fractures. Two laboratory experiments were conducted to provide data for validation of the numerical model, one dealing with steady flow in a Hele-Shaw cell and one with steady flow through a bed of packed glass beads. A horizontal fracture, extending from the upstream boundary to a point within the embankment, was used in both experiments, and it was shown to have a significant influence on the discharge, pressure distribution, height of the seepage face, and free surface profile. Comparisons between numerically determined and experimentally measured results were carried out with respect to the discharge, pressure distribution, height of the seepage face, and free surface profile. In the experiments it is shown that a fracture increases the discharge and that the discharge increases more when a fracture is located far away from the free surface profile than when it is located close to the free surface profile. The height of the seepage face above the tailwater is strongly dependent upon the length of the fracture. The influence on the free surface profile is greater when a fracture is close to the free surface profile than when it is far away from the free surface profile. These effects are also found in the numerical simulations. It is thus concluded that the agreement is generally satisfactory between the experimental and numerical results

  • 234.
    Billstein, Mats
    et al.
    Luleå tekniska universitet.
    Svensson, Urban
    Luleå tekniska universitet.
    Johansson, Nils
    Luleå tekniska universitet.
    Development and validation of a numerical model of flow through embankment dams: comparisons with experimental data and analytical solutions1999Inngår i: Transport in Porous Media, ISSN 0169-3913, E-ISSN 1573-1634, Vol. 35, nr 3, s. 395-406Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The development and validation of a numerical simulation model of the flow through embankment dams is described. The paper focuses on basic verification studies, that is, comparisons with analytical solutions and data from laboratory experiments. Two experimental studies, one dealing with the flow in a Hele-Shaw cell and the other with the flow through a bed of packed glass beads, are also described. Comparisons are carried out with respect to the phreatic surfaces, pressure profiles, seepage levels and discharges. It is concluded that the agreement between experimental, analytical and numerical results is generally satisfactory

  • 235.
    Bjelkevik, Annika
    Luleå tekniska universitet.
    Stability of tailings dams: focus on water cover closure2005Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Mining activities have been ongoing for thousands of years within Sweden. As the results of previous activities are evident today, i.e. for example acid mine drainage (AMD), the focus and interest on closure and remediation of mine sites and tailings storage facilities (TSFs) has increased. At present all mines in operation have closure plans according to legal requirements. The purpose of a closure plan is to make sure that the site is safe when the mine comes to an end and the mining company abandons the site. The need for remediation of TSFs, where the fine (crushed and milled) waste material, i.e. tailings, from the process plant is stored, is important with regard to the consequences for the future environment. The composition of the tailings vary, i.e. content of chemicals, minerals etc., from mine site to mine site. Unwanted processes taking place in the tailings within the TSF may result in acidic leachate and leaching of metals and heavy metals from the TSF. These processes will be harmful for the environment and must therefore be prevented or reduced to levels that the environment can handle. They need to be controlled through a proper remediation and closure design of the facility. One method to control these processes is by covering the impoundment with water. One of the most important requirements when using this method is the stability of the tailings dams surrounding the impoundment. Without stable tailing dams the water cover will not stay. Long term stability of tailings dams has been the focus of this research project. Long term has in this case been set to 1000 years or more, which has become an international praxis in the last couple of years. To understand what we need to know in order to achieve long term stable tailings dams several areas have been studied. One idea used, was that we need to know, and understand, how tailings dams in operation perform today in order to understand how they may perform in a long term perspective. This resulted in studies of tailings dam safety in Sweden (see Benckert , 2003 and 2004) and of incidents and failures at Swedish tailings dams (see Bjelkevik, 2005b and 2005c). Another field of importance is the properties of tailings and for dam stability purposes the mechanical properties of tailings as a construction material. Sampling and laboratory tests where performed in 2002/2003 in order to compare the properties of tailings with natural materials (see Bjelkevik and Knutsson, 2005a). The conclusion drawn is that tailings have different properties compared to natural materials and the way of testing tailings material need to be calibrated for these differences. It was also concluded that this is a field requiring much more attention in the future. The focus of this thesis has been the long term dam stability and the factors and processes affecting this. In the State of the Art report (Bjelkevik, 2005d) this is covered and discussed. The most important factors for long term dam stability are: the hydraulic gradient and its relation to internal erosion extreme events like floods, drought, high winds, earthquakes etc. slow deterioration processes like erosion, weathering, frost and ice forces etc. These aspects have been analysed and discussed within the thesis. One valuable source for improving our knowledge on long term stability is natural analogies that have been stable since the last glacial period. Another valuable source is ancient structures, like man made earthen mounds and dams. Existing knowledge of some of these types of structures are presented in the thesis. The author, however, believes that there are a lot more information and knowledge to gain from analysis of these types of structures. Finally, the conclusions from this research project are: no Swedish tailings dams can be regarded as long term stable today it is possible to design long term stable tailings dams more knowledge can be gained from natural analogies and ancient structures the most challenging aspects in designing long term stable tailings dams are probably not the technical aspects, but the non-technical In order to be able to define criteria for long term stable tailings dams several areas need further attention and research. Examples of these areas are: internal erosion long term changes in material properties the effect of the hydraulic gradient on slope stability interaction between tailings material and sealing elements/foundation within the tailings dam external erosion seepage points

  • 236.
    Bjelkevik, Annika
    Luleå tekniska universitet.
    Swedish tailings dams incidents and failures: lessons learnt2005Inngår i: Securing the future: international conference on mining and the environment, metals and energy recovery : proceedings, Stockholm: SveMin , 2005, s. 105-116Konferansepaper (Annet vitenskapelig)
  • 237.
    Bjelkevik, Annika
    Luleå tekniska universitet.
    Water cover closure design for tailings dams: state of the art report2005Rapport (Annet vitenskapelig)
    Abstract [en]

    When a mine comes to an end and the operation closes down the whole site will be abandoned. Thus there is a need for remediation of the tailings storage facility (TSF), where the fine (crushed and milled) waste material, i.e. tailings, from the process plant is stored. The composition of the tailings vary, i.e. content of chemicals, minerals etc., between different mine sites. Unwanted processes may take place in the tailings and an example of this is acid mine drainage (AMD), which result in acidic leachate and leaching of metals from the tailings. Processes of this type will be harmful for the environment and must therefore be prevented or reduced. There is a need to have them controlled. This state of the art report starts with a review of terms related to tailings dams and remediation of tailings dams. Definitions an/or explanations of different terms in the context of the report are given. For example long term is the time period for which tailings dams should be designed for at remediation. This term is explained and discussed. Long term is here thousands of years, or in a philosophical sense to the next glacial period, after which we do not expect man made structures above ground to be standing. The most common construction methods for tailings dams are presented, as well as the construction methods used for Swedish tailings dams in operation. Several differences and similarities occur in comparison with water retention dams (WRDs), which are highlighted. In order to find out the performance of Swedish tailings dams, failures and incidents have been investigated and analyzed during the last 60 year period. Even though the data is incomplete, the conclusion drawn is that tailings dams are not safe enough today, to be regarded as long term stable without measures taken. In order to prevent unwanted processes, such as AMD, in a long term perspective, different cover methods for the tailings have been developed. In this report the focus has been on the water cover method, where the tailings is covered with water. For a successful water cover design the most important conditions to be fulfilled are the long term water balance and physical stability of surrounding dams. The key factor is the long term stability of dams, which is discussed in the report. Processes affecting the stability of the tailings dams are presented, such as slope stability, hydraulic gradients and its relation to internal erosion, slow deterioration processes (weathering, erosion, frost and ice, vegetation and animal intrusion etc.). One factor affecting the dam safety quite considerably is the climate change. This is briefly discussed and references are given to ongoing work. In order to find out how long term stable dam structures should be designed to be stable during long periods of time, natural analogies and ancient mounds can be studied. Some examples of both types are described and discussed in the report. The aim of this report has been to document the existing knowledge on long term tailings dam stability. The intention has also been to analyse areas requiring extended knowledge in order to reach the goal with design and construction of long term stable tailings dams. Areas needing more research are identified. The document thus provides a platform for further research and is aimed to be a strategic document in the communication between the industry, authorities and organisations in the public sector. The final conclusion from this study is that criteria for long term stable tailings dams can hardly be defined today. More research is needed and more experience must be gained before specific design criteria can be given. Considering the limited knowledge of long term stability of tailings dams there is a demand for more studies. Some of the important processes identified here in this aspect are: - Internal erosion- Long term changes in material properties- The effect of the hydraulic gradient on slope stability - Interaction between deposited tailings and sealing elements/foundation within the tailings dam- External erosion on slopes- Seepage points

  • 238.
    Bjelkevik, Annika
    et al.
    Tailings Consultants Scandinavia AB.
    Knutsson, Roger
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dam stability: How to verify the actual stability?2016Konferansepaper (Fagfellevurdert)
    Abstract [en]

    Mining operations produce huge volumes of waste products. Tailings, the fine grained waste material, is often managed in tailings management facilities (TMFs) surrounded by dam structures, i.e. tailings dams. Stability of tailings dams, amongst other things, is an in-creasing concern as tailings dams continue to fail. There is not just one single reason why dam failures occur. Dam stability is, however, one of the keystones required for good tailings management and good tailings dam safety. Dam stability can be divided into two main parts: a) stability analysis and b) surveillance and monitoring. The first is carried out at the initial design (normally by consultants) and is thereafter updated during operation of the TMF. A commonly used method for the analysis is the limit equilibrium method (LE). Here a factor of safety (FS) is calculated and in Sweden this is normally 1,5. In order to verify the behavior of the dam surveillance and monitoring is used. Typically pore pressures, horizontal and vertical movements and seepage are monitored in order to find changes in the trend of readings or to identify unexpected behavior. There is, however, no way of linking the readings to the stability analysis as the LE analyses are based on analysis of the conditions at failure. Thus it is not possible to describe the behavior of the dam before failure and the monitoring cannot be used to “give” warning signals before failure. This paper describes a case study where advanced numerical modelling, have been used to determine deformations in the dam structure, which have been verified by inclinometer readings. It has been possible to verify the actual stability for the dam as it has been possible to link in-situ readings to the model. The concept described is not only applicable to tailings dams, but can also be used for any type of dam.

  • 239.
    Bjelkevik, Annika
    et al.
    Sweco AB.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Failures and incidents at Swedish tailings dams: experiences and comparisons2006Inngår i: Twenty-Second International Congress on Large Dams: 18 - 23 June 2006, Barcelona, Spain, [transactions], International Commission on Large Dams , 2006, Vol. III, s. 81-100Konferansepaper (Fagfellevurdert)
  • 240.
    Bjelkevik, Annika
    et al.
    Luleå tekniska universitet.
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Swedish tailings: comparison of mechanical properties between tailings and natural geological materials2005Inngår i: Securing the future: international conference on mining and the environment, metals and energy recovery : proceedings, Stockholm: SveMin , 2005, s. 117-129Konferansepaper (Annet vitenskapelig)
  • 241.
    Björklind, Malin
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Soil profile analysis by vibration theory and the natural frequency: Applied on a case project2018Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    To explore soil conditions at sites of infrastructure projects a number of geotechnical soundings are performed at appropriate intervals. Results are, in the nature of their set up, limited to the specific points at which the sounding is performed. To safely assume the area between bore holes a new method is applied and tried at the case railroad project Stenkumla – Dunsjö. By applying vibration theory in conjunction with the studied soils’ geodynamic properties the natural frequency for the soil can be calculated. The properties of the natural frequency also makes it possible to detect in vibration measurements. The method studied in this master thesis is that of utilizing the natural frequency of the soil to try and establish a soil profile from vibration measurements.  An important step in the method is to transform the vibration with the Fast Fourier Transform algorithm. This allows the comparison and analysis of natural frequencies. The measurements were performed by using and attaching an accelerometer to a train.  Results are partly transformed measurement data in frequency graphs and partly natural frequency calculations according to the site investigations. These are compared in the analysis section to try to confirm the methods’ reliability and to see if the method can be used to refine geotechnical investigations.  The reliability of the method is tested by watching for the expected frequencies from the calculations in the measurement data.  The method show more consistency closer to the ground surface rather at greater depths. It is also more reliable for stark contrast layers, i.e. if the soil layers have much of the same properties then it is difficult to spot the differing natural frequencies, as they are too similar.  In trying to establish the soil profile between bore holes the method is inconclusive, partly due to the fact that the investigated area consists of relatively alike soil layers that make the result graphs difficult to get information from. However, the suggested soil profiles from the analysis of this part of the master thesis bear resemblances to bore holes close by, so the method can be usable in some regard. Quality of measurement results would probably be better by running the train faster than was done in this master thesis. The quality of the analysis would also benefit from performing specific soundings to establish the soils’ geodynamic properties rather than using recommended empirical formulas as were used here.  The primary possible application for this method is to use it as a prioritizing tool at an early stage in infrastructure projects. Running the vibration measurement and getting a preliminary picture of the soil conditions could act as a way of steering investigations resources to where greater shifts in the data occur. 

  • 242.
    Bobaker, Aiman M.
    et al.
    Chemistry Department, Faculty of Science, University of Benghazi, Benghazi, Libya .
    Alakili, Intisar
    Chemistry Department, Faculty of Science, University of Benghazi, Benghazi, Libya .
    Sarmani, Sukiman B.
    School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bandar Baru Bangi, Malaysia.
    Al-Ansari, Nadhir
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Yaseen, Zaher
    Sustainable Developments in Civil Engineering Research Group, Faculty of Civil Engineering, Ton Duc Thang University, Ho Chi Minh City, Vietnam.
    Determination and Assessment of the Toxic Heavy Metal Elements Abstracted from the Traditional Plant Cosmetics and Medical Remedies: Case Study of Libya2019Inngår i: International Journal of Environmental Research and Public Health, ISSN 1661-7827, E-ISSN 1660-4601, Vol. 16, nr 11, s. 1-14, artikkel-id 1957Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Henna and walnut tree bark are widely used by Libyan women as cosmetics. They may contain lead (Pb), cadmium (Cd) and arsenic (As), which, in turn, pose a high risk to their health. This study aims to determine the levels of Pb, Cd and As in henna and walnut tree bark products sold in Libyan markets. The products were analyzed for their Pb, Cd and As content by using inductively coupled plasma mass spectrometry (ICP-MS) after a microwave acid digestion. The results showed a significant difference between the henna and walnut tree bark samples in terms of their heavy metals content (p < 0.05). The highest heavy metal concentrations were observed in the walnut tree bark samples whereas the lowest was observed in the henna samples. In addition, 60% of the henna and 90% of the walnut tree bark samples contained Pb levels and approximately 80% of the henna and 90% the walnut tree bark samples contained Cd levels, which are much higher than the tolerance limit. However, As concentrations in all the samples were lower. The results indicated that such cosmetics expose consumers to high levels of Pb and Cd and hence, to potential health risks. Thus, studying the sources and effects of heavy metals in such cosmetics is strongly recommended.

  • 243.
    Bolton, Malcolm D.
    et al.
    University of Cambridge, Department of Engineering.
    Gui, Meen-Wah
    National Taipei University of Technology, Department of Civil Engineering.
    Garnier, Jacques Ph
    Laboratory Cent. Ponts & Chaussees, Nantes.
    Corté, Jean François
    Laboratory Cent. Ponts & Chaussees, Nantes.
    Bagge, G.
    Technical University of Denmark, Lyngby.
    Laue, Jan
    Ruhr-Universität, Bochum.
    Renzi, R.
    ISMES Istituto Sperimentale Modelli e Strutture, Bergamo.
    Centrifuge cone penetration tests in sand1999Inngår i: Geotechnique, ISSN 0016-8505, E-ISSN 1751-7656, Vol. 49, nr 4, s. 543-552Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    When performing centrifuge tests, it is necessary to carry out in-flight tests such as the cone penetration test (CPT). Recently, miniature CPTs have formed one collaboration entitled 'European Program of Improvement in Centrifuging' (EPIC). This article provides information on both the random and the consistent variations which have been observed with CPTs in sand when identical prototypes have been modeled in the different laboratories.

  • 244.
    Bonath, Victoria
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Edeskär, Tommy
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Lintzén, Nina
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Fransson, Lennart
    Cwirzen, Andrzej
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Byggkonstruktion och brand.
    Properties of ice from first-year ridges in the Barents Sea and Fram Strait2019Inngår i: Cold Regions Science and Technology, ISSN 0165-232X, E-ISSN 1872-7441Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    First-year ice ridges are one of the main load scenarios that off-shore structures and vessels operating in ice-covered waters have to be designed for. For simulating such load scenarios, the knowledge gap on ice mechanical properties from the consolidated part of first-year ridges has to be filled. In total 410 small-scale uniaxial compression tests were conducted at different strain rates and ice temperatures on ice from the consolidated layer of 6 different first-year ridges in the sea around Svalbard. For the first time uniaxial tensile tests were performed on ice from first-year ridges using a new testing method. Ice strength was evaluated for different ice type, which are determined for each specimen based on a proposed ice classification system for ice from first-year ridges. 78% of all samples contained mixed ice with various compounds of brecciated columnar and granular ice. Ice strength of mixed ice showed isotropy, except for the samples containing mainly columnar ice crystals. For horizontal loading, mixed ice was stronger than columnar and granular ice. The residual strength of ductile ice depended on the strain rate. At 1.5% strain remained 70% of peak strength at 10−4 s−1 and 50% at 10−3 s−1. Ductile failure dominated for 75% of all mixed ice tests at 10−3 s−1 and − 10 °C. Ductile compressive strength was generally higher than brittle compressive strength for mixed ice. Brine volume was the main parameter influencing the tensile strength of the mixed ice which was between 0.14 MPa and 0.78 MPa measured at constant ice temperature of −10 °C.

  • 245. Bondarchuk, Alexander
    et al.
    Ask, Maria
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Dahlström, Lars-Olof
    Nordlund, Erling
    Knutsson, Sven
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Hydromechanical numerical analysis of rock mass behavior under a Swedish embankment hydropower dam2009Inngår i: Long Term Behaviour of Dams: Proceedings of the 2nd International Conference, 12th-13th October 2009, Graz, Austria / [ed] Erich Bauer; Stephan Semprich; Gerald Zenz, Graz: Verl. der Techn. Univ. Graz , 2009, s. 113-118Konferansepaper (Fagfellevurdert)
  • 246.
    Bonthron, Björn
    et al.
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Jonsson, Christian
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser.
    Geogrids in cold climate: Temperature controlled tensile tests & Half-scale installation tests at different temperatures 2017Independent thesis Advanced level (professional degree), 20 poäng / 30 hpOppgave
    Abstract [en]

    Due to the findings of extensive damage on geogrids used in a road embankment in northern Sweden, the Swedish Transport Administration (TRV) started to investigate the reason of these damages. Since the geogrids were installed at low temperature, below 0°C, it was suspected that the damages were connected the low temperature.

    To analyse whether low temperatures have an influence on the extent of installation damages, both a half-scale setup and temperature controlled tensile tests have been carried out on geogrids.

    In total five different types of geogrids have been tested; 3 extruded polypropylene geogrids, 1 woven PET geogrid, and 1 welded PET geogrid. All geogrids had an aperture size of approximately 35 mm and specified tensile strength of approximately 40 kN/m.

    The Half-scale tests was conducted by building a small road embankment inside a freeze container, at the Luleå University of Technology (LTU). The embankment contained crushed aggregate, type 0-70 mm, and geogrids. The purpose of the half-scale test was to simulate installation of geogrids at different temperatures and thereby investigate whether low temperatures have an influence on the rate of installation damages.

    The half-scale test was done for each type of geogrid at the temperatures: +20°C, -20°C and -30°C. First, the geogrid was covered by 150 mm of crushed aggregate. Then a vibratory plate (160 kg) was used to compact the crushed aggregate. After each installation, the crushed aggregate was removed carefully by vacuum suction. The geogrid was removed and then analysed by visual control and tensile tests conducted according to ISO 10319:2008 (wide width tensile test).

    Results from the half-scale tests indicate that 2 out of 5 of the tested geogrids were affected by the testing procedure. The results indicate that:

    -        one of the geogrids of polyprophylene (here referred to as G2) was more damaged at lower temperatures compared to installation at +20° C.

    -        the geogrid of woven PET (here referred to as G5) was less damaged at lower temperatures compared to installation at +20° C.

    Results for the other geogrids are either inconsistent or shows no significant variation of the measured parameters as function of temperature. Hence, these results cannot be interpreted as damage during installation.

    Temperature controlled tensile tests were done by tensile testing single strands from the geogrids to failure, inside a temperature controlled chamber. The purpose of these tests was to investigate how the strength properties of the geogrids are affected by low temperature. The test was repeated 5 times for each geogrid and temperature (+20°C, 0°C, -10°C and -20°C). Force and strain was measured during the tests.

    The results from the temperature controlled tensile tests show that the maximum strain decreases with lower temperature for all tested geogrids. The maximum strain decreased by 16% - 49% when the temperature dropped from +20°C to -20°C.

    The results show that the tensile strength increases with lower temperature for all tested geogrids except for the welded PET geogrid (here referred to as G1). For G1 the tensile strength decreased by approximately 7% at a temperature drop from +20°C to -20°C.

    For the woven PET geogrid (G5) and the polypropylene geogrids (G2-G3) the tensile strength increased between 13%-45% at a temperature drop from +20°C to -20°C.

    The E-modulus increased at lower temperature for all tested geogrids. The secant E-modulus at 2% strain increased by 13%-71% at a temperature drop from +20°C to -20°C.

    Summarized conclusions from the tests:

    Strength properties changed for all tested geogrids as the temperature decreased. All tested geogrids got stiffer at lower temperatures. The magnitude of the effects is different for different geogrids.

    The tensile strength increased with lower temperature for all tested geogrids except for the welded PET geogrid, which got lower tensile strength at lower temperature.

    The half-scale test indicates that the amount of installation damages at geogrids can be dependent of the temperature at installation. However, these indications can only be seen at two out of five tested geogrids. The effect cannot be connected to a specific step in the installation procedure and cannot be explained by the results from the temperature controlled tensile tests.

    The results from the half-scale test have a statistically low reliability since only one installation for each temperature and geogrid type was done. The compaction equipment used during the test was small, and had low compaction energy compared to a vibratory roller compactor commonly used in construction work.

    With respect to the discussion above, further studies should be focusing on developing the half-scale test. It is suggested that the test is scaled up to a full-scale test in order to simulate a real installation as close as possible. The test should also be conducted several times for each geogrid at each temperature in order to enable statistical analyses.

  • 247.
    Bouchelaghem, Fatiha
    et al.
    Sorbonne Universites, UPMC Univ Paris .
    Pusch, Roland
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi.
    Fluid flow and effective conductivity calculations on numerical images of bentonite microstructure2017Inngår i: Applied Clay Science, ISSN 0169-1317, E-ISSN 1872-9053, Vol. 144, s. 9-18Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Hydraulic conductivities of compacted water-saturated bentonite were computed based on the real microstructure. The Homogenization of Periodic Media approach employed fully acknowledges the heterogeneous and multiscale microstructure of clay, as well as locally varying physical flow properties. Consequently, three levels of description were considered : the microscopic level of clay particles, the mesoscopic level of clay aggregates, mineral grains and inter-aggregate porosity, and the macroscopic level of the sample subjected to fluid pressure gradients in the laboratory. Starting from the local description of fluid flow, the expression of the effective hydraulic conductivity tensor was derived. The soft and dense gels and the open voids may form a connected flow path or remain occluded. The local problems were solved on the microstructure obtained from a digitalized micrograph by image analysis. The contribution to macroscopic flow by the soft and dense gels was investigated in various configurations, and comparisons were made with hydraulic conductivity data for MX-80 bentonite.

  • 248.
    Bowman, Elisabeth T.
    et al.
    Department of Civil and Natural Resources Engineering, University of Canterbury.
    Imre, Bernd
    Institute for Geotechnical Engineering, ETH Zurich.
    Laue, Jan
    Institute for Geotechnical Engineering, ETH Zurich.
    Springman, Sarah M
    Institute of Geotechnical Engineering, ETH Hönggerberg, Zürich, Institute for Geotechnical Engineering, ETH Zurich.
    Experimental modelling of debris flow behaviour using a geotechnical centrifuge2010Inngår i: Canadian geotechnical journal (Print), ISSN 0008-3674, E-ISSN 1208-6010, Vol. 47, nr 7, s. 742-762Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Physical modelling of debris flows has been carried out in the geotechnical drum centrifuge at ETH Zürich. A new apparatus to model debris flows in the centrifuge is described. The apparatus permits the final reach of a typical debris flow to be modelled within the centrifuge, with unconsolidated material flowing down a slope to deposit as a fan around the drum. Experiments are described for both fixed base conditions and erodible bases. Tests to examine the verification (modelling) of models show that debris flow behaviour is governed mainly by friction and consolidation processes, although some resolution is required between flow behaviour downslope and flow arrest during runout. The results are compared with bulk parameters determined for field-scale debris flows. It is found that some important flow mechanisms, such as contact-dominated behaviour and high pore pressures, are developed that are closer to those developed at fieldscale than tests conducted at 1g. Velocity profiles for erodible beds are compared with a semi-empirical expression derived for experimental debris flows at 1g. Normalized velocity profiles are found to be in agreement; however, absolute velocities differ from those predicted. Scaling, the limitations of the apparatus, and potential for future work are discussed

  • 249.
    Bowman, Elisabeth T.
    et al.
    University of Canterbury.
    Imre, Bernd
    Institute for Geotechnical Engineering, Eidgenossische Technische Hochschule Zurich.
    Laue, Jan
    Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, Geoteknologi. Institute for Geotechnical Engineering, Eidgenossische Technische Hochschule Zurich.
    Springman, Sarah M.
    Institute for Geotechnical Engineering, Eidgenossische Technische Hochschule Zurich.
    Geotechnical centrifuge modelling of debris flows2007Inngår i: International Conference on Debris-Flow Hazards Mitigation: Mechanics, Prediction, and Assessment, Proceedings, 2007, s. 229-239Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A granular debris flow may grow in size through erosion of its substrate, resulting in an increased hazard through greater mass, speed and runout. Exactly what governs the erosion potential of a particular flow is a matter of some debate, however, with apparently similar conditions producing very different entrainment behaviour. Some theories use an extension of sediment transport models that involve the removal of soil through a shear stress applied by the flow. However, comparison of field and laboratory-scale data suggests that other processes, such as undrained loading of the bed, are also likely to have influence at large scales. Hence properties of the bed need to be considered as well as the characteristics of the flow material. The modelling of erosion processes at laboratory scale is generally limited by the low stresses applied by the soil-water mixture at small scale. Modelling flows in a geotechnical centrifuge overcomes this problem by increasing the g-level, therefore allowing for correct prototype stress levels to be accounted for at small scale. This paper describes the development and use of a model debris flow apparatus on a geotechnical drum centrifuge at ETH in Zurich, Switzerland. Preliminary tests have been undertaken to compare fixed and erodible bed conditions - enabling erosion processes to be examined at prototype stress levels. © 2007 Millpress.

  • 250.
    Bowman, Elisabeth T.
    et al.
    University of Canterbury.
    Laue, Jan
    Institute for Geotechnical Engineering, Eidgenossische Technische Hochschule Zurich.
    Imre, Bernd
    Institute for Geotechnical Engineering, Eidgenossische Technische Hochschule Zurich.
    Zweidler, Adrian
    Institute for Geotechnical Engineering, Eidgenossische Technische Hochschule Zurich.
    Springman, Sarah M.
    Institute for Geotechnical Engineering, Eidgenossische Technische Hochschule Zurich.
    Debris flows in a geotechnical centrifuge2006Inngår i: Physical Modelling in Geotechnics, 6th ICPMG'06: Proceedings of the 6th International Conference on Physical Modelling in Geotechnics, 2006, Vol. 1-2, s. 311-316Konferansepaper (Fagfellevurdert)
    Abstract [en]

    A new apparatus to allow the examination of laboratory debris flows at prototype stress levels within a geotechnical drum centrifuge is described. The apparatus consists of a curved aluminium flume that lies within the circumference of the drum, the inclination of which can be altered from 0 to 40 degrees. PPTs may be placed in the base and along one aluminium side wall, while the other wall is made from Perspex, to enable viewing of the flow during a test. A tube at the head of the flume enables flow materials to be introduced after preparation external to the centrifuge, while tests may be carried out with both fixed and erodible beds. A high speed camera is used to capture images of the flow during centrifuge flight. Initial tests suggest a maximum particle size of 4mmmay be introduced to the flow.The influence ofwater content and fluid viscosity is discussed. © 2006 Taylor & Francis Group, London.

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