| 1. |
- Zardari, Muhammad Auchar, et al.
(författare)
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Numerical Analyses of Earthquake Induced Liquefaction and Deformation Behaviour of an Upstream Tailings Dam
- 2017
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Ingår i: Advances in Materials Science and Engineering. - : Hindawi Publishing Corporation. - 1687-8434 .- 1687-8442. ; 2017
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Tidskriftsartikel (refereegranskat)abstract
- Much of the seismic activity of northern Sweden consists of micro-earthquakes occurring near postglacial faults. However, larger magnitude earthquakes do occur in Sweden, and earthquake statistics indicate that a magnitude 5 event is likely to occur once every century. This paper presents dynamic analyses of the effects of larger earthquakes on an upstream tailings dam at the Aitik copper mine in northern Sweden. The analyses were performed to evaluate the potential for liquefaction and to assess stability of the dam under two specific earthquakes: a commonly occurring magnitude 3.6 event and a more extreme earthquake of magnitude 5.8. The dynamic analyses were carried out with the finite element program PLAXIS using a recently implemented constitutive model called UBCSAND. The results indicate that the magnitude 5.8 earthquake would likely induce liquefaction in a limited zone located below the ground surface near the embankment dikes. It is interpreted that stability of the dam may not be affected due to the limited extent of the liquefied zone. Both types of earthquakes are predicted to induce tolerable magnitudes of displacements. The results of the postseismic slope stability analysis, performed for a state after a seismic event, suggest that the dam is stable during both the earthquakes
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| 2. |
- Johansson, Teddy, 1960-
(författare)
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Artificial Ground Freezingin Clayey Soils : Laboratory and Field Studies of Deformations During Thawing at the Bothnia Line
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Artificial ground freezing as a method to temporarily stabilize and create hydraulic sealing in urban as well as in rural areas has been used in a number of Swedish construction projects, particularly during the last decade. One problem with the freezing of soil and rock is that fine-grained clayey types of soils have showed a tendency to under certain circumstances, during the thawing process, create a pore water overpressure and to consolidate, despite a change in the external loading conditions. In certain cases, this condition can be a desired effect as the soil mass after a freeze- and thaw cycle acquires overconsolidated properties. The main objectives of this study are, to describe and review the knowledge and current state of practice of artificial ground freezing, to increase the understanding about the conceptual behaviour for prognosis of the vertical deformation concerning artificial ground freezing and to compare and discuss results from laboratory and field studies concerning vertical deformation during thawing process for Bothnia soil. The field studies and the laboratory tests in this research study have been performed with soil from the freezing of the Bothnia Line in the vicinity of Stranneberget. The Bothnia Line is the railway link between Nyland, north of Kramfors, and Umeå. This thesis relates to a part of the Bothnia Line. It deals with the behaviour of soil during thawing by means of temporary stabilization and hydraulic sealing of fine-grained soil through artificial freezing using brine as the cooling agent. However, the reason behind the problem consists of the final deformations due to the thawing process. The general conclusions of this study are; the Bothnia soil water content decreased in mean approximately 14 % after a freeze-thaw cycle, which approximately corresponds to; wth = 0.8w – 1.5 the decrease of the water content has no correlation to the depth below ground surface, in contrast, there is a strong correlation between the undisturbed soil water content and the magnitude of the decrease in water content the soil liquid limit decreases after a freeze-thaw cycle, simultaneously as the relative share of clay and fine silt grains decreases while the relative share of more coarse grains increases the coarser and denser soil created after a freeze-thaw cycle obtains an increased preconsolidation pressure and an increased undrained shear strength.
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| 3. |
- Sissakian, Varoujan, et al.
(författare)
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Geomorphology, Geology and Tectonics of Jabal Sanam, Southern Iraq
- 2017
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Ingår i: Journal of Earth Sciences and Geotechnical Engineering. - : Scientific Press International Limited. - 1792-9040 .- 1792-9660. ; 7:3, s. 97-113
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Tidskriftsartikel (refereegranskat)abstract
- Jabal Sanam is an outstanding geomorphological feature in south of Iraq located50 Km southwest of Basrah city; along the border with Kuwait. It stands high in a vast flat plain with elevation of 140. 61 m (a.s.l.). The relief difference between the highest point; on top of Jabal Sanam and the surrounding flat plain ranges from (108 –127) m. The E – W and N- S diameters of Jabal Sanam are 355.97 m and 489.45 m, respectively, whereas, the E – W and N – S diameters of the surrounding first circular rim are 1524.11 m and1857.90 m, respectively. The exposed rocks in the surroundings belong to the Dibdibba Formation (Pliocene – Pleistocene); show clear Hogback and Cuesta forms. The rocks of the Nfayil Formation (Middle Miocene) are exposed in the near surroundings of the intruded body; they are crushed, deformed and faulted. All the exposed rocks along the rims show clear dipping towards the outer rim forming dome like structure. Beds of gypsum and black dolomite are also exposed in the central part of the dome, most probably intruded from deep lying beds. Other crushed rocks; some of them are igneous are also present, especially in the central part of the intruded body. The estimated age of those crushed rocks is Infra-Cambrian, as indicated from pollen and spores found in coal seams within the exposed sequence.The presence circular rims surrounding Jabal Sanam may indicate multi rising processes of the exposed sequence of the intruded body. All the previous works confirm the origin to be a salt plug; using gravity data. However, the current study hasused evidences of Neotectonic activity to support the salt plug assumption too.
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| 4. |
- Al-Ani, Thair, et al.
(författare)
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Trace elements in water and sediments of the Tigris river, Baghdad City, Iraq
- 2014
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Ingår i: Journal of Environmental Hydrology. - 1058-3912 .- 1996-7918. ; 22
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Tidskriftsartikel (refereegranskat)abstract
- Industrial, agricultural and rural activities may result in pollution of watercourses with elevated trace metal concentrations and implications for water supply and ecosystem functioning. The concentration of the trace metals Fe, Mn, Zn, Co, Pb, Cu, and Cd in the water and clay fractions (<2μm) of the bank sediments of River Tigris in Baghdad city were determined. Dissolved trace metals concentrations were far below the upper permissible limits during 2012-2013. There was no consistent pattern between element concentrations and river discharge. Seasonal interrelations between water and sediments were most obvious for Fe that decreased in both environments with rising flows during autumn. Although independent of discharge, Mn in water and sediments often followed each other at all stations. Zinc, however, increased in the sediments and decreased in the water with discharge. The clay fractions were slightly to strongly enriched in trace metals with the gradient Co > Fe > Zn > Mn > Cu suggesting absorption of the metals on sediment substrate.
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| 5. |
- Al-Ansari, Nadhir, et al.
(författare)
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Effect of treated wastewater irrigation on vegetables
- 2013
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Ingår i: Journal of Environmental Hydrology. - 1058-3912 .- 1996-7918. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- Treated waste water is normally used for irrigation purposes in countries suffering from water shortages to narrow the gap between supply and demand. The concept behind this is to save water consumed for agricultural activities, which consumes most of the water, for municipal and industrial uses. The Alsukhna area in Jordan is used to grow vegetables which are irrigated by treated wastewater. Surface and groundwater samples from the Zarqa region were analyzed for their major cations, anions and heavy metals. The impact of the treated waste water on the chemical components of vegetables was studied using Zn, Mn, Fe, Pb and Ni in sweet and hot pepper, tomato, cauliflower, cabbage, squash, cucumber and eggplant which were compared with similar vegetables irrigated by natural unpolluted water from the Mafraq region. The four metals, namely Zn, Fe, Pb, and Ni, had concentrations higher than in the reference vegetables by 3423%, 155%, 397%, 2949% and 289%, 187%, 211%, 214% fortomato and cauliflower, respectively. Sweet pepper was mainly influenced by an increased content of Fe, which was almost 180% higher than that in sweet pepper from the Mafraq region. Hot pepper had highly elevated concentrations of Ni (6980%) and Zn (419%), while squash demonstrated high Zn (207%) and Pb (666%). When all the heavy metals are considered, the most affected vegetable is the hot pepper with an average percent of heavy metals accumulation of 1559% while the least effected is cabbage at 116%.
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| 6. |
- Alakangas, Lena, et al.
(författare)
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Literature review on potential geochemical and geotechnical effects of adopting paste technology under cold climate conditions
- 2013
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The purpose of this literature review is to summarize the recent research regarding geochemical and geotechnical stability of paste tailings, identify knowledge gaps and future research needs. The present study has been conducted by the Division of Geosciences and Environmental Engineering together with the Division of Mining and Geotechnical Engineering at Luleå University of Technology on behalf of Boliden Mineral, LKAB and Outotec.A survey conducted by MEND (Mine Environment Neutral Drainage) in 2006 on the environmental effects related to the use of paste tailings summarizes that only a few studies had been performed about long-term effects on the surface and groundwater quality. Instead, the focus had been on the additives and the strength of the paste. It is still uncertain how the paste technology affects the long-term environmental stability from a geochemical point of view. Concerns regarding the stability of paste with high sulphide content are still relevant. Studies performed indicate that sulphide oxidation occurs within cemented paste as well as on the surface of non-cemented paste and cracks formed on the surfaces could induce oxidation. For cemented paste, metals released by sulphide oxidation might be sequestered due to high pH induced by the alkaline additives, but anion such as Se has been shown to be mobilized. The leachate has been shown to be near-neutral initially, but the neutrality decreases with time and probably metals sequestered in the matrix will also be released. Again, it should be noted that no long term study was performed on leaching of paste, cemented or uncemented. The longest leaching study was performed for one year. Arsenic has been proven to be retained in Ca-arsenates in cemented paste, but the long term stability of these precipitates is relatively unknown. Expanded secondary phases e.g. gypsum and ettringite have been observed to form when there is sulphate in the process or drainage of water. These phases could crack the paste, but, on the other hand, can also fill former cracks when deposited in layers. The effects of the formation of these phases are relatively uncertain in a long-term perspective. Presence of different elements such as ammonium, sulphates and metals in the water has been shown to negatively affect the curing process and therefore water is suggested to be treated before use. The presence of carbon dioxide during the paste formation could also affect the curing process, but could sequester metals in carbonate phases.Geotechnical and rheological properties of paste is well defined and documented. Several case studies have been found in literature providing valuable information about the details of the works being carried out. However, a difficulty has been noted during the investigation of the effects of cold climate conditions when current practice is applied in the colder parts of the world. It is not certain how some specific and vital parameters are going to be affected by cold temperatures. Parameters such as deposition slopes and deposition scheme, strength development of the paste are expected to be responsive to cold climate conditions. There are predictions about which properties are going to be affected in what way, but there is also a need to establish a scientific base for discussion. These have been highlighted as research needs and information gaps at the end of the report.
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| 7. |
- Bernander, Stig, et al.
(författare)
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Downhill progressive landslides in long natural slopes: triggering agents and landslide phases modeled with a finite difference method
- 2016
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Ingår i: Canadian geotechnical journal (Print). - : Canadian Science Publishing. - 0008-3674 .- 1208-6010. ; 53:10, s. 1565-1582
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
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| 9. |
- Hatem, Mohammed, et al.
(författare)
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Rheological Properties of Cement-Based Grouts Determined by Different Techniques
- 2014
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Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; 6:5, s. 217-229
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Tidskriftsartikel (refereegranskat)abstract
- The rheological properties of cement-based grouts containing talc or palygorskite were investigated for optimizing fluidity and quick strengthening at injection. The fluidity controls the ability of grout to penetrate fractures and can be determined by pipe flow tests, Marsh funnel tests, mini-slump cone tests and rheometer tests. The grouts were 1) Talc for fluidity and strength by reacting with cement, 2) Palygorskite (attapulgite) for early gelation by being thixotropic, and 3) Powdered quartz for chemical integrity. The freshly prepared grouts behaved as Bingham fluids with viscosities from 0.151 to 0.464 Pas and yield stresses 5.2 Pa to 36.7 Pa. Statistical analysis of the flow test data converted Marsh flow time into viscosity. The pipe flow tests gave 26.5% higher values than the viscometer for grout with Portland cement and talc, and about 13.7% lower than the viscometer data for the grout with low-pH cement and talc. The big Marsh funnel gave valuesdiffering by 5.2% - 5.3% from those of the viscometer for grout with talc and Portland, and Merit 5000 cements. For grout with palygorskite the viscosity was at least twice that of the other grouts. Grout fluidity was positively affected by talc and negatively by palygorskite and early cement hydration
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| 10. |
- Knutsson, Sven, et al.
(författare)
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Project: Internal erosion in embankment dams
- 2010
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Annan publikation (populärvet., debatt m.m.)abstract
- Since older embankment dams have a tendency to gradually display an increased degree of leakage it is interesting to find out if this phenomenon can be captured by an inverse modelling approach. Numerical tests with a model system will hopefully lead to a better understanding of the decomposition of material in dams and enhance the knowledge about the long term effects in order to forsee potential problems in the future.These embankment dams typically consist of a central core of moraine that is surrounded by a filter, a transition layer and a fill material. Ideally the seepage through the dam is relatively small and the effect on the dam from the flow is negligible. However, in reality there are several situations that promote a fatal failure of the dam including overtopping at high flood discharges, internal erosion and seepage problems in the embankment and the foundation. The status of embankment dams are generally examined by in-situ measurement of one or several of the following quantities: pore pressure, inclination and settlement, temperature, resistivity, self-potential, seepage rate, turbidity of the seepage water, ground penetration radar and bore hole tomography. These indirect and/or discrete methods give indication of the condition of the dam leaving the real situation for the imagination. Hence, when there are alterations to measured values great efforts are often spent on reinforcing dams in order to keep a high safety level. An increased knowledge of the composition of material in dams would enable the usage of focused measures reducing the costs and increasing the safety.
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