| 1. |
- Bhanbhro, Riaz, et al.
(författare)
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Basic description of tailings from Aitik focusing on mechanical behavior
- 2013
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Ingår i: International Journal of Emerging Technology and Advanced Engineering. - 2250-2459. ; 3:12, s. 65-69
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 2. |
- Bhanbhro, Riaz, et al.
(författare)
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Mechanical Properties of Soft Tailings from a Swedish Tailings Impoundment : Results from Direct Shear Tests
- 2014
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Ingår i: Electronic Journal of Geotechnical Engineering. - 1089-3032. ; 19:Z, s. 9023-9039
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Bhanbhro, Riaz, et al.
(författare)
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Mechanical Properties of Soft Tailings from different Depths of a Swedish Tailings Dam : Results from Triaxial tests
- 2020
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Ingår i: Scientia Iranica. International Journal of Science and Technology. - Tehran : Sharif University of Technology, Scientia Iranica. - 1026-3098 .- 2345-3605. ; 27:3, s. 1066-1074
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
- Arnesson, Marcus, et al.
(författare)
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Naturvärden i lövträdsmiljöer runt Värnanäs
- 2007
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Området vid Värnanäs har tidigare pekats ut för att ha internationella naturvärden. De inventeringar som presenteras här i rapporten bekräftar detta med många och mycket ovanliga arter. Den gemensamma nämnaren för de flesta av arterna är de gamla och grova träden framför allt av ek och bok. I samband med trädinventeringen noterades 2681 värdefulla träd, både levande träd, döda liggande, döda stående och högstubbar. Det största trädet är en ek med en omkrets på 969 cm. Eken tillhör med stor sannolikhet ett av landets tio största träd. Sammanlagt finns tio träd i området med en omkrets på över 6 meter, av dessa är nio ekar och en bokhögstubbe. Hela 66 inmätta träd har en omkrets på över 5 meter. Anmärkningsvärt är även den grova sälgen vid Halltorpsån med en omkrets på 450 cm samt tallen med en omkrets 482 cm, båda tillhör de absolut största av sitt trädslag i Sverige. I trädinventeringen noterades 1227 håliga lövträd av dessa var 446 ekar och 397 bokar. Där fanns också en hel del grova högstubbar och döda stående träd. Totalt noterades 56 bokar och 97 ekar som hade en brösthöjdsdiameter >40 cm. Sätts gränsen till >99 cm blir antalet 19 bokar och 30 ekar. Grova lågor är extremt sällsynt i dagens landskap men inom det inventerade området påträffades 59 bokar och 140 ekar med en basdiameter >40 cm. Sätts gränsen till >99 cm blir antalet 5 bokar och 30 ekar. Under 2006 inventerades vedlevande skalbaggar, fjärilar, lavar och svampar och 2004 inventerades fladdermöss. Antalet funna rödlistade arter bara under 2006 var: 65 skalbaggar, 6 fjärilar, 16 svampar och 14 lavar. Undersökningarna är inte heltäckande och flera tidigare funna arter som sannolikt finns kvar i området hittades inte under 2006. Området hyser också en rad rödlistade arter ur andra organismgrupper, noterat är bland annat 3 fladdermöss, 2 grod- och kräldjur samt 19 fåglar. En förutsättning för att behålla naturvärdena är att trygga förekomsten av gamla träd i området och spara alla former av död ved. Det finns ett stort behov att röja runt äldre träd. Det är också viktigt att skötseln görs på ett sådant sätt att antalet skyddsvärda träd ökar på sikt. En annan förutsättning är att de förekommer i en mosaik av öppna och halvöppna områden. Allt detta kräver skötsel i form av röjningar och bete. På de igenväxta markerna bör restaurering med efterföljande betesdrift ske snarast för att inte naturvärden ska gå förlorade. Ett annat problem, främst i bokbestånden, är att åldersblandningen homogeniserats via gallringar. För att naturvärdena på sikt ska bestå och utvecklas måste de gamla träden få tillräckligt med utrymme och nya gammelträd kontinuerligt bildas. Detta är mycket svårt att förena med produktionsinriktad skogsskötsel. Inventeringen av skyddsvärda träd ingår i det nationella åtgärdsprogrammet för skyddsvärda träd i kulturlandskapet. Området berörs av nio olika åtgärdsprogram och utöver det ovan nämnda är följande åtgärdsprogram aktuella för området: skalbaggar i eklågor (där svart guldbagge och brunoxe ingår), hotade bokskogsarter (där bokblombock och rombjätteknäppare ingår), läderbagge, havsörn, långbensgroda, sandödla, större vattensalamander och knubbsäl (Östersjöbestånd).
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| 5. |
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| 6. |
- Arup, Ulf, et al.
(författare)
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Professor Ingvar Kärnfelt - a birthday tribute
- 2009
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Ingår i: The Lichenologist. - Cambridge : Cambridge University Press. - 0024-2829 .- 1096-1135. ; 41:5, s. 453-456
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- On 19 July 2009 Ingvar Kärnefelt celebrated his 65th birthday. This could have meant that we, his former students, would be celebrating him in his retirement from his position as head of the Biological Museums at Lund University. We are grateful that this is not the case, as Ingvar will carry on, probably for at least one or two more years. Instead, we celebrate Ingvar because he is the main reason for all of us having studied lichenology in Lund. This special issue of The Lichenologist is dedicated to him as a birthday tribute in honour of his long and fruitful lichenological career. The main authors of all the papers in this issue are former students of Ingvar. For several of us he has not only acted as supervisor but later also as the director of the Botanical Museum where we meet him in our daily work.
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| 7. |
- Berglund, Andreas, et al.
(författare)
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Comparison between temperature based thaw weakening prediction model and field observation methods
- 2011
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Ingår i: Proceedings of the 21st International Conference on Port and Ocean Engineering under Arctic Conditions. - Montreal.
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 8. |
- Bhanbhro, Riaz, 1985-, et al.
(författare)
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Effect of Particle Size On Mechanical Properties and Particle Breakage of Tailings
- 2017
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Ingår i: Canadian geotechnical journal (Print). - 0008-3674 .- 1208-6010.
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Bhanbhro, Riaz, et al.
(författare)
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Evaluation Of Primary And Secondary Deformations and Particle Breakage of Tailings
- 2015
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Ingår i: From Fundamentals to Applications in Geotechnics. - : IOS Press. - 9781614996026 - 9781614996033 ; , s. 2481-2488
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Konferensbidrag (refereegranskat)abstract
- 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.
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| 10. |
- Bhanbhro, Riaz, et al.
(författare)
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Mechanical Behavior of Uniformed Tailings Material in Triaxial Tests
- 2017
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Ingår i: Electronic Journal of Geotechnical Engineering. - : Mete Öner. - 1089-3032. ; 22:06, s. 1717-1730
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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