| 1. |
- Knutsson, Roger, 1987-, et al.
(författare)
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Geothermal Study of a Tailings Deposit : Frost Line Modelling and Comparison to Field Data
- 2021
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Ingår i: Journal of Earth Sciences and Geotechnical Engineering. - : Scientific Press International Limited. - 1792-9040 .- 1792-9660. ; 11:3, s. 15-32
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Tidskriftsartikel (refereegranskat)abstract
- Seasonal freezing and thawing can have significant effects on tailings management. Tailings delivery, depositional schemes and water treatment are examples of activities that must be dealt with extra concern in sub-zero temperatures. Changes in mechanical properties, drainage possibilities or embedded frozen tailings layers are effects that can arise in poorly managed facilities. To avoid such consequences, a good understanding of the seasonal effects on the tailings deposit is needed. To get a better understanding of the geothermal regime in tailings, this paper presents a case study with geothermal modelling performed for the Laiva tailings facility in Finland, where major seasonal freezing and thawing periods are present. Ground temperatures and frost lines were predicted via one-dimensional modelling using air temperatures and snow cover depths from adjacent weather stations, and basic soil properties from the facility. Simulated results were compared to data obtained from thermal instruments in the field. The snow cover and its estimated thermal properties were shown to have large influence on the results. The model was able to accurately predict the thermal regime measured in the field. Strong agreement was shown, both in terms of ground temperatures and frost front positions. The methodology presented is useful for tailings management schemes in cold regions.
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| 2. |
- Knutsson, Roger, 1987-, et al.
(författare)
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How to avoid permafrost while depositing tailings in cold climate
- 2018
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Ingår i: Cold Regions Science and Technology. - : Elsevier. - 0165-232X .- 1872-7441. ; 153, s. 86-96
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Tidskriftsartikel (refereegranskat)abstract
- Managing tailings deposition in cold climate requires specific measures not to create permafrost. The risk of generating permafrost due to tailings deposition exists even in regions where permafrost would naturally not occur. Material being frozen during winter might not fully thaw in the following summer due to added height of the tailings on the surface. Such embedded layers of permafrost should be avoided especially close to tailing dams. Main reasons are to prevent impermeable layers in tailings facilities, and to reduce the risk of having implications if such layers thaw during warmer summers causing increase in pore water pressure, reduced effective stress, and increased water content.This paper presents a numerical study on the effects of tailings deposition in cold regions in relation to the potential formation of permafrost. Various deposition rates, schedules and tailings properties were evaluated. One-dimensional heat conduction analyses were performed with a temperature scenario representing a mine district in northern Sweden. Results show, that the thickness of permafrost layers increase with increased deposition rate and with increased water content. It was also shown that wet and loose tailings must be deposited in short periods during summer to avoid permafrost generation. In the case of dry and dense tailings more time is available for deposition in order not to cause aggradation of permafrost in the deposit.These findings can help mining operation to set up deposition schedules for tailings facilities in cold climate. For known tailings properties, results can be used to identify periods of the year when, and how much, tailings can be deposited in critical areas of a deposit in order to avoid permafrost formation.
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| 4. |
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| 5. |
- Wiklund, Viktor, 1993-, et al.
(författare)
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Towards better understanding of CPT data on tailings
- 2023
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Characterization of tailings deposits is associated with significant challenges in tailings dam design and dam safety assessments. One of the challenges is static liquefaction in the deposited tailings and how this has to be addressed in stability assessments. Concerns have led to design concepts that deposited tailings considered susceptible to liquefaction, will liquefy. Facillities should therefore be designed for such post-liquefaction scenario, i.e. fluidized tailings. Existing upstream-constructed tailings dams are seldom built for a design case with post-liquefaction strength in the tailings. Consequently, mining companies must take dam safety-enhancing measures and rapidly conduct major changes in their tailings dam design.At the same time, there are questions and uncertainties in evaluating static liquefaction potential in tailings that must be addressed. The uncertainties are, among others, related to differences between natural sands and tailings. There is a need to address the applicability of today’s evaluation methods on tailings and this paper will describe how a research project at Luleå University of Technology, funded by Boliden, will investigate and address the uncertainties in the evaluation. Cone Penetration Testing (CPT) in a calibration chamber will be undertaken in the project. A new calibration chamber for CPT is developed, where silty-sandy tailings material will be tested in a controlled laboratory environment. Combined with other laboratory test results, the CPT calibration chamber results will be used to derive new and update existing correlations between CPT data and tailings properties. The research will focus on the mechanical properties of tailings and its influence on the soil behavior around the penetrating cone. This paper will highlight uncertainties in state interpretation from CPT in tailings, present the design work of the calibration chamber and the expectations for the outcome of the CPT calibration chamber research.
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| 6. |
- Abdullah, Twana, et al.
(författare)
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Assessment of groundwater vulnerability to pollution using two different vulnerability models in Halabja-Saidsadiq Basin, Iraq
- 2020
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Ingår i: Groundwater for Sustainable Development. - : Elsevier. - 2352-801X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Groundwater aquifer in Halabja-Saidsadiq Basin considered as one of the most important aquifers in terms of water supplying in Kurdistan Region, NE of Iraq. The growing of economics, irrigation and agricultural activities inside the basin makes it of the main essentials to the region. Therefore, pollution of groundwater is of specific worry as groundwater resources are the principal source of water for drinking, agriculture, irrigation and industrial activities. Thus, the best and practical arrangement is to keep the pollution of groundwater through. The current study aims to evaluate of the vulnerability of groundwater aquifers of the study area. Two models were applied, to be specific VLDA and COP to develop maps of groundwater vulnerability for contamination. The VLDA model classified the area into four classes of vulnerability: low, moderate, high and very high with coverage area of (2%,44%,53% and 1%), respectively. While four vulnerability classes were accomplished dependent on COP model including very low, low, moderate and high vulnerability classes with coverage areas of (1%, 37%, 2% and 60%) respectively. To confirm the suitability of each map for assessment of groundwater vulnerability in the area, it required to be validated of the theoretical sympathetic of current hydrogeological conditions. In this study, groundwater age evaluated utilizing tritium isotopes investigation and applied it to validate the vulnerability results. Based on this validation, the outcome exhibits that the vulnerability classes acquired utilizing VLDA model are more predictable contrasted with the COP model.
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| 7. |
- Abdullah, Twana, 1977-
(författare)
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Groundwater Vulnerability Assessment to pollution in Different Soil and Rock Materials
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The augmentation of human population regularly corresponds with change in the land cover, including expansion of urban areas, which imposes increasing the available amount of domestic and drinking water. The study area, Halabja-Saidsadiq Basin, is situated in the Northeast of Iraq and is one of the major groundwater sources of the region. As the surface water sources are not enough in the studied area, it has become necessary to use groundwater at an increasing rate. Usually, a huge amount of groundwater is plentiful in the alluvial deposits or rock outcrops where the urban areas are frequently situated. Such areas face a huge risk of pollution of groundwater due to producing different sources of a contaminant from human's activity. Keeping these aspects in view, groundwater vulnerability studies have been carried out in the current studied basin. The main objective of this work is to investigate the environmental impacts on groundwater quality and recognize the groundwater vulnerability in the area so that the groundwater can be protected from probable contaminations.In the current study, DRASTIC model has been applied since it is one of the most proper useful methods available for the assessment of the groundwater vulnerability. This model has been modified in different ways to achieve the obvious vulnerability condition in the area; likewise, different further methods have been applied for comparison purposes such as: weight modified VLDA and standard COP models. In addition, the applied models were validated by comparing its findings against the estimated groundwater ages and the observed water characteristic qualities within the region in two successive seasons.According to the spatial distribution of irrigation water quality index, groundwater at the studied basin classified into three group for both dry and wet seasons, namely, Sever Restriction (SR), High Restriction (HR) and Moderate Restriction (MR). The coverage area of all three classes are (1.4%, 52.4% and46.2%) for dry season and (0.7%, 83.3% and16%) for wet seasons, respectively. While, refer to the water quality index for drinking purpose, groundwater in this basin reveals a permissible to excellent groundwater quality of the dry season and a good to excellent groundwater quality of the wet season. The high level of a good groundwater quality in the wet season compared to the dry season might be expected to the groundwater recharge during the winter and spring periods, which lead to dilution of chemical component, in contrast high irrigation and agricultural activities and groundwater discharge in the dry season leads to increase the concentration of chemical component.Field and official data were collected to review several environmental impacts and were used to map standard DRASTIC vulnerability model for the study basin. Based on this model, the study area was classified into four zones of vulnerability indexes, comprises a very low, low, moderate and high vulnerability index with a coverage area of (34%, 13%, 48% and 5%) respectively.In the first modification step, the rate and weight value of each parameter in DRASTIC model is modified. Nitrate concentration from 39 groundwater samples was used for modifying the recommended standard rating value based on the Wilcoxon rank-sum nonparametric statistical test and then sensitivity analysis was used to modifying recommended standard weighting value of each parameter. To calibrate the modified rate, the Pearson's correlation coefficient was applied to estimate the relation between DRASTIC values and nitrate concentrations in groundwater samples. For the first modified model, the correlation coefficient was 72% that was significantly higher than 43% achieved for the standard model. The modified model classified the area into five vulnerability classes, including (very low, low, moderate, high and very high) with covered area of (7%, 35%, 19%, 35% and 4%), respectively.The second modification of DRASTIC model was based on land use and land cover for the studied area. The land use and land cover (LULC) map prepared using ERDAS IMAGINE software from two different scenes of Landsat Thematic Mapper (TM). The LULC map indicates that only five classes of LULC can be identified: these are: barren land, agricultural land, vegetation land, urban area and wet land or water body. The modified DRASTIC based on LULC map classified the area into five classes with different coverage area of each class: very low (1.17%), low (36.82%), moderate (17.57%), high (43.42%) and very high (1.02%).The third modified method of the current study is the modification of DRASTIC model based on Lineament feature of the study basin. A lineament map is extracted from Enhanced Thematic Mapper plus (ETM+) satellite imagery using different techniques in remote sensing and GIS. The lineament density map demonstrates that only six classes of lineament density can be identified ranged from (0-2.4). The third modified DRASTIC model classified the area into four vulnerability categories: very low (28.75%), low (14.31%), moderate (46.91%) and high (10.03%).The fourth effort to modify standard DRASTIC model is the application of Analytical Hierarchical Process (AHP) to assess the weight value of each parameter. The modified DRASTIC vulnerability index values based on AHP method ranged between (65.82–224.1) with five vulnerability classes comprises (very low to very high).Weight modified VLDA and standard COP models were also applied to map vulnerability system in the study basin. The vulnerability outcome based on weight modified VLDA model revealed that a total of four ranges of vulnerability indexes had been distinguished ranging from low to very high with vulnerability indexes (2.133-9.16). Subsequently, based on the standard COP model, the area is also divided into four vulnerability classes ranging from very low to high with index value ranged from (0.79) to (6.2).All applied models in the study basin were compared to each other and validated to clarify the validity of the theoretical sympathetic of current hydrogeological conditions and to show the accuracy of the modeled vulnerability system. Two methods were applied for the validation of the result, in the first approach; nitrate concentration analysis has been selected; the nitrate differences between two following seasons (dry and wet) were analyzed from (39) water wells. In the second approach, groundwater vulnerability was assessed based on estimated groundwater age from range of tritium (3H) value in the groundwater samples from different groundwater aquifers in the studied area. The results of both validation methods verify the sensibility of the gradation and distribution of vulnerability levels acquired using the modified DRASTIC model based on (rate and weight modification, weight modification based on AHP process and effect of LULC on DRASTIC model) and also applying weight modified of VLDA model.
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| 8. |
- Abdullah, Twana, et al.
(författare)
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Hydrogeochemical Evaluation of Groundwater and Its Suitability for Domestic Uses in Halabja Saidsadiq Basin, Iraq
- 2019
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Ingår i: Water. - Switzerland : MDPI. - 2073-4441. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- Evaluation of the hydrogeochemical characteristics and groundwater suitability for domestic use was conducted in the Halabja Saidsadiq Basin in the northeastern part of Iraq. The total studied area is about 1278 km 2 with a specific Mediterranean-type continental interior climate, which is cold in winter and hot in summer. To conduct the required laboratory chemical analysis for groundwater samples in the studied basin, 78 groundwater samples, in total, were collected from 39 water wells in the dry and wet seasons in 2014 and analyzed for major cations and anions, and the results were compared with the permitted limits for drinking water. An examination of the chemical concentrations of the World Health Organization drinking water norms demonstrate that a large portion of the groundwater samples is suitable for drinking, and a preponderance of groundwater samples situated in the class of hard and very hard water types for both seasons. Suitability of groundwater for drinking use was additionally assessed according to the water quality index classification. This showed that more than 98% of groundwater samples have good water quality in the dry and wet seasons. Conversely, the classification of groundwater samples based on Piper’s diagram designates that the groundwater type is alkaline water, with existing bicarbonate along with sulfate and chloride. However, water–ock exchange processes and groundwater flow have been responsible for the dominant water type of Ca–g–CO3.
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| 9. |
- Abdullah, Twana O., et al.
(författare)
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Magnitude and Direction of Groundwater Seepage Velocity in Different Soil and Rock Materials
- 2020
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Ingår i: Engineering. - USA : Scientific Research Publishing. - 1947-3931 .- 1947-394X. ; 12:4, s. 242-253
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Tidskriftsartikel (refereegranskat)abstract
- To understand and anticipate flow in various groundwater media, the magnitude and direction of groundwater flow velocity must be deemed. The studied area which is called Halabja-Sadiq Basin is in the northeastern part of Iraq and covers an area of approximately 128,000 square hectometers. There are several groundwater aquifers in this region that supply nearly over 90% of all water needs. Subsequently, it is of highly requirement to identify various groundwater behaviors in the area. The objective of this study is to estimate the magnitude and direction of the groundwater seepage velocity with the aid of groundwater tool in Geographic Information System technology. Refer to the results of this analysis, the magnitude value of groundwater flow velocity ranged from 0 to 51 m/d, whilst the general flow movement is from the eastern part to the western part of the study area. The factor governing the direction of flow and velocity magnitude indicates the direction of dipping of the geological formation strata, the high head of groundwater in the eastern part, and the low transmissivity properties of aquifer materials in the western part.
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| 10. |
- Abdullah, Twana, et al.
(författare)
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Possibility of Groundwater Pollution in Halabja Saidsadiq Hydrogeological Basin, Iraq Using Modified DRASTIC Model Based on AHP andTritium Isotopes
- 2018
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Ingår i: Geosciences. - : MDPI. - 2076-3263. ; 8:7
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Tidskriftsartikel (refereegranskat)abstract
- An anthropogenic activity is one of the most severe environmental causes for groundwatercontamination in the urban area. Groundwater thought to be one of the principal sources of water supply in Halabja Saidsadiq Basin, and therefore its vulnerability evaluation to define areas that are more vulnerable to pollution is incredibly vital. The objectives of this paper are to reveal weight modified of DRASTIC model based on the Analytical Hierarchical Process to estimate the proportional likelihood of groundwater resources pollution. Tritium isotopes analysis was chosen and applied as a pollution marker to confirm the result of this adjustment. Based on this modification, vulnerability classes that were achieved for the studied basin were alienated into five classes, including very low, low, medium, high, and very high, with vulnerability index value of (<100, >100–125, >125–150,>150–200, and >200), respectively.
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