| 1. |
- Al-Jabban, Wathiq Jasim
(författare)
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Soil Modification by adding small amounts of binders : A laboratory study
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soil stabilization through addition of a hydraulic binder is a method frequently used to modify and improve engineering properties of soft soils. Additives like cement and lime are typically used as stabilizers. More recently, industrial by-products, such as fly ashes, cement kiln dust, blast furnace slags and other slags have been used. The chemical reaction between the soil and the stabilizer alters the physical and engineering properties of the soil and thus desired strength and durability are obtained. The choice of appropriate type and quantity of stabilizer (binder) depends largely on factors such as soil type, moisture content, organic content, sulfate content, curing conditions (time and temperature) and the desired improvement.The objective of this thesis is to increase knowledge and understanding of how small amounts of binders change various engineering properties of stabilized soils in short- and longtime perspective. Extensive laboratory and field programs have been carried out. They cover immediate and long-term effects on the engineering properties by adding various binders. Cement, Multicem, and by-products Petrit T and Mesa were used as binders. Binder was added to the soil at various quantities: 1%, 2%, 4%, 7% and 8% of soil dry weight. The field and laboratory investigation included tests of consistency limits, sieving and hydrometer, unconfined compressive strength, density, solidification, grain size distribution using laser particle size analyzer, leaching tests and pH value. The tests were carried out on the treated soil with different binder contents and after different curing times i.e. 7, 14, 28, 60, 90 days for laboratory tests and 7 and 35 days for field investigation.The unconfined compression tests were used to show the effects of different binders on the enhancement in strength and stiffness over time. Consistency limits were determined to investigate the effects of the binders on the consistency limits, directly after treatment and over time. Laser particle size analyzer tests were conducted to investigate the effects of different binders on the particle size distribution (PSD) before and after treatment. The pH tests were conducted to investigate the effects of different binders on the alkalinity of the soil immediately after treatment and over time. This was used to give an indication of soil-binder reactions. MRM leaching tests were conducted to investigate the acidification potential of soils before and after treatment. Freeze-thaw cycles were conducted to investigate the strength characteristics after freezing and thawing in short- and long-term perspectives. Visual observation and standard dry sieving tests were conducted to optimize the proper mixing times to disintegrate or homogenize the soils by decreasing the size of agglomerated soil particles.The results show, that the variation in soil strength and stiffness of the treated soils are linked to different chemical reactions. Cement is most effective in improving the physical and engineering properties compared to the other binders studied. The plasticity index of soil decreases after treatment and over time. Liquidity index and the ratio of water content to plastic limit are introduced as new indices to illustrate the improvement in workability of treated soil by measuring the reduction in the liquidity index. This is found directly after treatment and it increases with time when the liquidity index is within the plastic range or when the water/plastic vi limit ratio is more than one. Increase of binder content and using longer curing times result in increase of soil density and decrease of water content. Particle size distribution of soil is changed by reducing the clay size fraction and increasing the silt size particles after treatment. This shows that an aggregation of particles take place resulting in coarser material than the initial. The cement-treated soils exhibit a more brittle failure in the unconfined compression tests compared to soils treated with other binder types where a more ductile behavior is observed. Applying freezing-thawing-cycles reduces the strength and stiffness of the treated soil.The appropriate length of time to homogenize and disintegrate the natural soil prior to treatment depends on several factors, such as soil type, water content, and plasticity properties of soil. For high plasticity soil, the disintegration time should be kept as short as possible. The homogenizing and disintegration time is less important for low plasticity soils with low water content than for medium to high plasticity soils.The acidification potential of soils are related to the addition of cementitious binders. The effect is found directly after treatment and over time. The treated soil exhibits higher resistance to decrease in pH value. The strength and stiffness properties found in the field investigation agree in general with those obtained from the laboratory investigation for the same binder type.
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| 2. |
- Al-Madhlom, Qais
(författare)
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Potential Use of Aquifer Thermal Energy Storage System in Arid Regions
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- After the Oil Crises in 1973, which meant higher energy costs, the world started to look for other sources of energy. This led to the development of renewable energy techniques. Because of the intermittent nature of renewable energy, storage systems were also developed. Underground Thermal Energy Storage (UTES) systems spread and are now globally well known. In these systems, excess thermal energy (heat or cold) is stored (short term and/or long term) from the surplus period to periods of higher demand. The storage media in such systems are underground materials, e.g. rock, soil, and/or groundwater. The current study aims to examine the use of underground thermal energy storage systems in arid regions, in order to increase the efficiency of both cooling and heating systems in these regions, such that CO2 emissions and consumed electricity for these purposes are reduced. Three main parameters determine which type of Underground Thermal Energy Storage (UTES) systemis most suitable. These are site, design, and operation parameters. The site-specific parametersinclude soil properties and all geo-hydrological, environmental, geological, metrologicalconditions. Therefore, the site parameters cannot be changed after installing the storage system,since they majorly depend on the location, while the other parameters (design and operation) canbe changed after construction. The first primary goal of this study is to find how and what site parameters involved to specify the most suitable type of UTES systems in arid regions. Thus, the suitable type of UTES systems can be decided. The second primary goal is to answer how and where to select the best location to install the adopted system. To achieve the goals of the study, two arid regions within Iraq were used as case studies. They are Babylon and Karbala, where the former is characterized by its shallow aquifer, while the latter is characterized by a relatively deeper aquifer. The ArcMap-GIS software was used to prepare the relevant digital maps, e.g. maps of hydraulic conductivity, population, type of soil, aquifers, groundwater elevation, transmissivity, and slope. Then, the vulnerability (readiness for being polluted by the surface contaminants) maps of the available aquifers were determined, followed by finding the seepage velocity of the groundwater. Depending on the outputs of the vulnerability and the seepage velocity, the most suitable type of Underground Thermal Energy Storage (UTES) systems can be decided. This study, also, includes developing/inventing a general methodology that can be used to determine the best location to install Underground Thermal Energy Storage (UTES) systems, including Aquifer Thermal Energy Storage (ATES) systems. The last part of this study includes applying the suggested methodology to determine the best location to install the suitable type of Underground Thermal Energy Storage (UTES) system in the study area. The first study was in the Babylon Province. Here, groundwater table is very shallow (less than 2 m depth in some regions). The crystalline bedrock is at a depth of 9-12 km below the ground surface, overlaid by 9-12 km of sedimentary rocks on which there is a 2-50 m thick layer of alluvial silty clay sediments. The groundwater moves slowly in this aquifer (2.12*10-6 - 1.85*10-1) m/d, and it is brackish having salinity of 5000-10000 mg/l. The susceptibility (vulnerability) of the aquifer in northern part of Babylon province is low to very low having ranges from 80 to 120 on Drastic model scale, which has the overall range of 26 – 226 (i.e. 0.27- 0.47 on normalized vulnerability). The second study area was a part of Karbala Province. This area can be divided into two regions based on the geology and geo-hydrological conditions. An eastern part is located on the Mesopotamian plain, and a western part is located in Western Desert. In both parts, the groundwater table is relatively deeper than the Babylon province. In the eastern part, it is generally more than 4 mbgs (meter below ground surface). While, in the western part it is deeper and reaches to 48 mbgs in depth. The soil in the eastern part is alluvial silty clay, while the western part consists of gypcrete sandy deposits. The groundwater, which flows towards the east, has a seepage velocity range from 0 to 0.27 m/d. The salinity of the groundwater changes from slightly brackish (1000-3000) mg/l in the western parts to highly brackish (5000-10000) mg/l in the Mesopotamian parts of the province. By comparing the site parameters of each province with the different UTES systems, the type of thermal energy storage system was decided. The most important site parameters are the depth of the water table and the aquifer characteristics. For Babylon Province, the expected suitable underground thermal energy storage system is an aquifer thermal energy storage system in silty clay. For Karbala Province, two systems are suggested: for the eastern part, aquifer thermal energy storage system in silty clay is recommended, while for the western part, a deep (10-30 m depth) sandy aquifer thermal energy storage system is recommended. After that, a methodology was developed and used to determine the suitable location in which to install the Aquifer Thermal Energy Storage (ATES) system. For Babylon province, the site selection index ranges between 2.9 and 5.3 on 1 to 10 scale. About 71% of the region has a site selection index ranges between 4.71 and 5.3. Concerning Karbala study area, the site selection index ranges between 3.1 and 9.1. About 15% of the region has a site selection index between 8.1 and 9.1.The energy saving in neighboring countries to Iraq by using the Aquifer Thermal Energy Storage (ATES) system ranges from 55% to 72%. It is also expected that using a ground sink heat pump instead of a conventional air-to-air heat pump increases the COP (Coefficient Of Performance) of roughly (10) to (-17). The negative sign means that the heat is injected into the ground. More theoretical and field studies are required to cover the different aspects of the subject of potential use of Aquifer Thermal Energy Storage (ATES) system in an arid region, and to verify the improvement of COP (Coefficient Of Performance) due to using these systems.
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| 3. |
- Chabuk, Ali
(författare)
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Solid Waste Landfills in an Arid Environment : Site Selection and Design
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Selecting landfill sites is considered a complicated task because its whole process is based upon several factors and restrictions. This study shows the present status of solid waste management, sources, collection personnel, machinery and equipment that are involved in the waste collection process, financing and financial management for the major cities of the Babylon Governorate in Iraq (Al-Hillah, Al-Qasim, Al-Mahawil, Al-Hashimiyah and Al-Musayiab). The management of waste collection and disposal in the Babylon Governorate and its districts is through open waste dumps, so the quality of the collection and disposal process is poor, and these sites do not conform to the scientific and environmental criteria usually applied in the selection of landfill sites.In the first part of the current study, three methods were used to calculate the solid waste quantity for each specific year up to the year 2030 as well as the cumulative quantity of solid waste for the period (2020-2030) for Babylon Governorate. The results show the cumulative quantity of solid waste resulting from (method 3) receives a high value compared to other methods, and so it is used as a maximum value to estimate the required area for candidate sites for landfills in each district. The generation rate in 2030 will be (0.97, 0.69, 0.48, 0.62 and 0.91) (kg/capita/day) in (Al-Hillah, Al-Qasim, Al-Mahawil, Al-Hashimiyah and Al-Musayiab), respectively, based on method 3, where the estimated annual incremental generation rate is 1 %. The second part of this study aims to find the best sites for landfills in the arid areas that are distinguished by a shallow depth of groundwater. The Babylon Governorate was selected as a case study because it is located in an arid area, and the depths beneath the ground surface to the groundwater level are shallow. For this purpose, 15 important criteria were adopted as follows: groundwater depth, rivers, soil types, agricultural land use, land use, elevation, slope, gas pipelines, oil pipelines, power lines, roads, railways, urban centers, villages and archaeological sites. These criteria were then entered into the geographic information system (GIS). The GIS software has a large capacity to manage and analyze various input data using special analysis tools. In addition, Multi-Criteria Decision Making (MCDM) methods were used to derive the relative weightings for each criterion in different styles. These methods are (Analytical Hierarchy Process (AHP), Simple Additive Weighting (SAW), Ratio Scale Weighting (RSW) and Straight Rank Sum (SRS)).Raster maps of the selected criteria were prepared and analyzed within the GIS software. The final map for candidate landfill sites was obtained through combining the GIS software and (MCDM) methods. Subsequently, comparison methods (Change Detection, Combination, Kappa and Overall Assessment) for each pair of raster maps that result from using the two different methods of multi-criteria decision making were implemented to determine the pixel percentage of matching and non-matching as well as to determine and check the suitability of the selected sites for landfills on both resulting maps using two methods. Two suitable candidate sites for landfills were determined to fulfill the scientific and environmental requirements in each major city. These areas are (6.768 and 8.204) km2 in Al-Hillah, (2.766 and 2.055) km2 in Al-Qasim, (1.288 and 1.374) km2 in Al-Hashimiyah, (2.950 and 2.218) km2 in Al-Mahawil, and (7.965 and 5.952) km2 in Al-Musayiab. The required area of the selected sites can accommodate solid waste from 2020 until 2030 based on the required areas according to the third method.The third part of this study includes soil investigations for the selected landfill sites. The suggested design should ensure that there is no groundwater pollution by leachate from these sites because the groundwater depth is very shallow in the Babylon Governorate. To avoid this problem, soil investigation was conducted at these sites so that the most suitable landfill design could be established. Each site was subjected to field soil tests to find the composition of the soil strata at each site to a depth of 10 m, and these results were compared with the soil properties adopted for final site selection. The Iraqi Ministry of Housing & Construction, National Centre for Construction Laboratories and Research Babylon, Iraq, carried out the analytical work on the soil in 2016. The results of the soil investigation at these sites include the soil profile, groundwater depth, chemical properties, allowable bearing capacity, atterberg limits test results and material characteristics of the soil strata. According to the results of these tests, the best design is the one that puts the compacted waste at the surface.The fourth part of this study covers the selection of a suitable proposed design in the arid areas (Babylon Governorate, Iraq) for the selected landfill siting. In the current study, the design of this landfill includes the suggested soil layers for the liner system and final cover system. For the base liner system (from the bottom toward the top), the composite bottom barrier layer consists of highly compacted sandy clay. The thickness of the bottom barrier layer is 60 cm, and its saturated hydraulic conductivity is 1.0E-7cm/s. The 1.5 mm thick geomembrane (HDPE), with hydraulic conductivity of 2.0E-13 cm/s, is placed over the composite bottom barrier layer. The leachate collection system consists of drainage layer (gravel) with a thickness of 30 cm and a hydraulic conductivity of 3.0E-1 cm/s. The diameter of the main drainpipes is between 15 and 20 cm. The protection layer consists of sand material, and its hydraulic conductivity is 5.0E-3 cm/s. The thickness of the protection layer is 30 cm.The compacted solid waste is placed upon the surface to a height of 2 m because of the shallow groundwater depth and to avoid groundwater contamination by leachate from the landfill site. The density of the compacted waste is 700 kg/m3, and its saturated hydraulic conductivity is 1.0E-5 cm/s.Three scenarios were used for the suggested designs for the final cover system of the landfills in arid areas. The first scenario was “evapotranspiration soil cover (ET) (capillary barriers type)”, the second scenario was a modified cover design of "RCRA Subtitle D", and the third scenario was the “Recommended design”. In this study, “Recommended design”, the third scenario for the final cover system, was adopted in the arid area (Babylon governorate, Iraq) based on combining certain layers from the first and second scenarios. For the three scenarios, the soil components in these designs used was based on available local materials in the study area. The layers of the base liner system were adopted in all scenarios.The third scenario for the final cover system, “Recommended design”, was implemented based on weather parameters in the arid areas. The water infiltrated from the surface of landfill is stored within upper layers that have fine particles. This allows the stored water to evaporate from the soil surface of the landfill or transpire through vegetation due to the high temperature during most months in the study area. The water that enters from the surface of the landfill should be contained above the geomembrane liner and top barrier layer without leakage into the waste body, thereby preventing leachate generation.For the layers of the final cover system (from the bottom to the top), the intermediate cover is used to cover the waste body, and this layer consists of moderate compacted silty clayey loam (native soil). The thickness of the intermediate cover is 30 cm, and its saturated hydraulic conductivity is1.0E-6 cm/s. The foundation layer consists of coarse sand material with a thickness of 30 cm and a saturated hydraulic conductivity of 1.0E-2 cm/s. This layer acts as a cushion for the layers of the final cover system. The gas collection system can be installed within the foundation layer. The top barrier layer is placed over the foundation layer. This layer consists of highly compacted sandy clay of (45 - 60 cm) thickness with compacted lifts (each lift is 15 cm). The saturated hydraulic conductivity of the barrier layer is 1.0E-7 cm/s. The geomembrane liner, (HDPE) of 0.5 cm thickness and a saturated hydraulic conductivity of 2.0E-13 cm/s, is put on top of the barrier layer. The upper layers of the final cover system are the support vegetation layer and the topsoil layer. The composition of the support vegetation layer is moderate compacted loam. This layer is placed directly on the geomembrane liner. The saturated hydraulic conductivity of the support layer is1.0E-5 cm/s, and its thickness is 45 cm. The topsoil layer consists of silty clayey loam, and it is placed over the support vegetation layer with a slope of 3%. The thickness of the topsoil layer is 15 cm, and its hydraulic conductivity is 4.0E-5 cm/s. The Hydrologic Evaluation of a Landfill Performance (HELP 3.95 D) model was applied to the selected landfill sites in the governorate to check if there could be any infiltration of the leachate that will result from the waste in the landfills in the selected sites in the future. The HELP model, which utilizes both weather and soil data, is the most commonly used model for landfill design, and it is employed to evaluate the quantity of water inflow through soil layers for the designed landfill. This suggested landfill is designed using the weather parameters (rainfall, temperature, solar, and the required date to calculate evapotranspiration) for the 12 consecutive years from 2005 to 2016, as well the required data for soil design.In the HELP model, the result for the suggested landfill design for both the recommended design (third scenario) and the second scenario was a modified cover design of "RCRA Subtitle D", which showed there was no leachate through the soil
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| 4. |
- Darwesh, Ali, 1966-
(författare)
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Parameters optimization of oil well drilling operation
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In the beginning of 2005, the ministry of natural resources in the Kurdistan region of Iraq dividedits territory into more than 50 oil blocks based on geological setting. These oil blocks were awardedlater to different international oil companies for oil investments based on Production SharingContracts (PSCs). A new oil-exporting pipe was also established from the region to the Jaihan portin Turkey at the Mediterranean Sea.This study is related to the oil well drilling operations in one of these oil blocks in northern Iraqwhich is referred as the Bazian oil block. Drilling operations in the nearby oil blocks (Taq Taq andMiran) were started earlier and the drilling data of those oil blocks were used as offset data in thedrilling program of the Bazian block. High similarities were expected between these oil blocks withrespect to lithology of the formations, oil well drilling techniques, and operation problems. By 2009over twenty oil wells were drilled in the Taq Taq oil block and it is becoming one of the mostimportant oil fields in the Kurdistan region. In the Miran oil block, exploration for oil and gas startedin early 2008, and three oil wells were completed and started to produce crude oil. By the end of2009, the geological and geophysical surveys in Bazian block were finished and the drilling operationstarted on October 1st the same year.This study (Parameter Optimization in Oil Well Drilling Operation) was recommended andsponsored by the Kurdistan Regional Governorate (KRG) aiming towards more optimized drillingin the future in the same oil block. Parameters like weight on bit, string rotation and rate ofpenetration for the future drilling operation in the Bazian oil block with more optimized valueswere predicted. This study was started by collecting detailed operational data from different sourcesduring the operations of drilling the Bazian well Bn-1. Among many sources of data, Mud LoggingUnit (MLU) data were selected for this study, as it was the most complete data set from the surfaceto the final drilled depth. This thesis contains the work of five published papers in the evaluation ofthe drilling operation at different intervals for the key well. Parameters for achieving the optimalpenetration rate were predicted for the future operations.The first paper (Evaluation of Limestone Interval in the Drilled Surface Section of Bn-1 Oil Well)was on the evaluation of the drilling operation in the surface section from 9 m to 480 m. The highlyfractured Pila Spi formation was studied for its controllable parameters like Weight on Bit (WOB),drill string rotation (RPM) and the used torque. High loss of circulation and environmental effectswere studied. Optimum drilling fluid, drilling technique, and drilling parameters were proposed forthe future drilling operation.In the second paper (Kicks Controlling Techniques Efficiency in Term of Time) recorded data wereanalyzed to manage the drilling operation during the critical times in terms of controlling the BottomHole Pressure (BHP). Productive and none productive times were analyzed through the study ofthe drilling and tripping operations. Change in the drilling technique was proposed by modifyingthe drilling fluid. Drilling fluid as a first barrier to control formation pressure and well kicks werestudied for their rheological properties. During the drilling operations two techniques, circulatingtechniques and non-circulating methods, were implemented to control the BHP. Both methodshave been implemented to control kicks in the Bn-1 oil well and wells in other oil blocks in theregion. The process of drilling design and casing setting points have been studied based on theutilization of accurate values of formation pressure. Data of formation pressures were used to designsafe mud weights to overcome and prevent well kicks. The emphasis has been placed on the practicalutilization of the kicks pressure near the reservoir. The presented relationships help in betterunderstanding of the lithological columns and reduce possible hole problems during the kickappearance. Optimum casing setting point of the intermediate section was proposed for futureoperations.The third paper (Time Optimizing near the Pay Zone) was on the drilling operation inside the caprock. Time managing was studied for surface preparation facilities, subsurface expected pressurecontrol time, and the best technique to control the Bottom Hole Pressure (BHP). Well controllingtechniques in oil and gas drilling operations are used to control BHP and avoid any fluid influx fromformation to the well. Time consumed to control the formation pressure will range between a fewhours to many days. This paper also discussed the hydrostatic pressure distribution and changes nearthe pay zone for the Bazian (Bn-1) oil well. Increasing linearly drilling fluid properties such as densityand viscosity with time will help the engineer to better interpret sampling of the lithological columnsand reduce possible hole problems.Paper number four (Wiper Trips Effect on Wellbore Instability Using Net Rising Velocity Methods)was on the effect of wiper trips operations to control parameters during the operations in two drilledshale formations, the Tanjero and Shiranish formations. Wiper trips were evaluated based on thelifting capacity of the cutting in the drilling fluid. This paper discussed the wiper trip effects on wellinstability in shale formations. The problematic shale interval sections were studied with respect tothe time spent on the wiper trip operations. Lifting efficiency and well wall instability arecontinuously changing with time. Detailed drilling operation, formation heterogeneity, rheologicaland filtration characteristics of the proposed polymer water-based mud were discussed. The physicaland chemical properties of the drilled formation and drilling fluid were also studied.Wiper trips were analyzed based on recorded history in relationship with the controllable parameters.Two calculation models have been implemented to find the net rising cutting particle velocity inthe annular. The relation between the net rising velocity and wiper trips were analyzed with supportof results from laboratory works. Strong relationships were found between the wiper trip effects andlithology types of the penetrated shale. A modified drilling program was proposed in relationship tothe casing setting point and drilling fluid properties that make the operations more optimized.The fifth paper (Controllable drilling parameter optimization for roller cone and polycrystallinediamond bits) predicts optimized Rate of Penetration (ROP), WOB and the string rotation (RPM– rotation per minute) for the entire drilled well. The most used empirical Bourgoyne and Youngmodel (BYM) for roller cone bits were used in the optimization process. This model describes theeffect of eight parameters in one mathematical equation. The BYM was adjusted to be applicablefor other types of drilling bits like polycrystalline diamond compacts (PDC) bits. Controllableparameters like WOB, RPM and ROP were clustered based on changes in Bottom Hole Assembly(BHA) and lithology before running the model.The implemented clustering and averaging method for the collected data in short lithologicalintervals were used to eliminate the effect of noisy data and to overcome the lithology homogeneityassumption used in other previous studies. A simpler model were introduced instead to optimize thestring rotation.Multiple regression techniques were used in each cluster to determine optimized controllable drillingparameters. Optimized ROP, WOB, and RPM were predicted for future drilling operations. Aclear relationship was found between the formation lithology and the controllable parameters ineach cluster.
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| 5. |
- Hassan, Rebwar, 1959-
(författare)
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Sediment Characteristics and Sedimentation Rate Estimation in the Dukan Reservoir
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Dukan Reservoir has been created from the construction of the Dukan Dam on the Lesser Zab River where it crosses the Khalakan Thrust Sheet (Khalakan Mountains) through a gorge 65 km northwest of Sulaimani and 295 km northeast of Baghdad. The Dukan Dam is a multi-purpose dam which was built from 1954 to 1959 to control the flooding of the Lesser Zab River, and to provide irrigation, hydroelectricity, and water storage. Reservoir sedimentation can significantly reduce reservoir storage capacity as dams become older. The Dukan Reservoir has been selected for this study to determine the nature and characteristics of the deposited sediment particles in the reservoir, as well as the estimation of the rate of sedimentation from 1959 to 2014 by using the bathymetric survey and the Soil and Water Assessment Tool (SWAT) model methods.Geologically, the Dukan Reservoir is located in the High Zagros Fold-Thrust Zone (High Folded Zone) of the northwestern segment of the Kurdistan Zagros Fold-Thrust Belt. This reservoir is a natural and structurally controlled depression located in the Btwen (Ranya) Agricultural Plain extending between the Ranya Thrust Sheet (Kewa-Rash Mountains) and the dam body itself. A geological survey was conducted for the study area and it has been concluded that the structural controls were more effective by dividing the Dukan Reservoir into two sub-reservoirs: a bigger triangle-shaped sub-reservoir in the north and a smaller irregularly shaped sub-reservoir in the south. The differences that exist in shapes, lengths, widths, surface areas, and shorelines between the two subreservoirs are also closely related to the structural and stratigraphical controls. The field observations and bathymetric survey indicate that bank sediment erosion is occurring in the two sub-reservoirs, but most of the sediment particles deposition takes place within the bigger sub-reservoir. Grain analyses of the 32 bed sediment samples show that the reservoir bed sediment consists of 15% gravel, 14% sand, 48% silt, and 23% clay. The sediments are composed of silty clay (77.6%), silty sandy clay (10%), sandy gravelly silty clay (1.2%) and gravelly sandy silty clay (1%). The reservoir bed is covered mainly with silt. Both silt and clay percentages increase towards the dam in the smaller sub-reservoir. This is attributable to the decreased water velocity in the reservoir, leading to the deposition of the suspended materials. The sediments are very finegrained, very poorly sorted, strongly coarse skewed, and mesokurtic. The depositedsediment along the Dukan Reservoir can be classified into topset bed (coarse particles) and bottomset bed (fine materials). The slope of the western bank of the reservoir is steeper than the eastern and northern banks. Land slope is the most effective factor in erosion and sediment transport. From the bathymetric survey, it has been also concluded that the minimum elevation which reaches 430 m.a.s.l. is located at the southern part of the bigger sub- reservoir. Based on different bulk densities of the deposited sediment at different water elevations, i.e., 1855 kg/m3 at 470 m.a.s.l., 1855 kg/m3 at 480 m.a.s.l., and 1200 kg/m3 at 480 m.a.s.l., the annual sedimentation rates in the reservoir are estimated to be about 3.8 MCM, 7 MCM, and 6.6 MCM, respectively. This estimation has been supported by the SWAT model method, which shows that the annual sediment load delivered to the Dukan Reservoir from the watershed is estimated to be about 1.3 MCM, representingabout 34% of the total sediments deposited in the reservoir.The reduction in storage capacity of the bigger sub-reservoir from 1952 to 2014 at water elevations 440 m.a.s.l., 460 m.a.s.l, and 480 m.a.s.l. are 72%, 48%, and 24%, respectively. The volume of the deposited sediment is estimated to be around 274 MCM. The percentage of the smaller sub-reservoir area as a percentage of the whole reservoir area varied in 1952 from 4% at water level 520 m.a.s.l. to 100% at 420 m.a.s.l. The author predicts that the estimated annual deposition rate of 6.6 MCM and the projected useful lifespan might extend for another 155 years until 2169, when the sediment will fully occupy the live storages.
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