| 1. |
- Chabuk, Ali, et al.
(författare)
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Soil Characteristics in Selected Landfill Sites in the Babylon Governorate, Iraq
- 2017
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Ingår i: Journal of Civil Engineering and Architecture. - : David Publishing Company. - 1934-7359 .- 1934-7367. ; 11:4, s. 348-363
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Tidskriftsartikel (refereegranskat)abstract
- The Babylon Governorate is situated in the middle of Iraq. It covers an area of 5,315 km2 and has 2,092,998 inhabitants distributed throughout its five major cities (Qadhaa). Presently, there is no landfill site in the governorate that meets the environmental criteria for the disposal of municipal and industrial waste. Consequently, GIS (geographic information system) and methods of multi-criteria decision making were used here to select the best sites in each city in the Babylon Governorate that would fulfil the environmental requirements. Two sites were chosen in each city. As the groundwater is very shallow in this area, the design should ensure against groundwater pollution by leachate from these sites. To avoid this problem, soil investigation was conducted at these sites so that the most suitable landfill design could be accomplished. The results of soil investigation in these sites include the soil profile, groundwater depth, chemical properties, allowable bearing capacity, Atterberg limits test results and material characteristics of the soil strata. From the research, it is believed that the best design is one that puts the landfill above ground.
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| 2. |
- Pusch, Roland, et al.
(författare)
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Long-term function of on-ground repositories for hazardous waste : Mechanisms in cyclicdrying/wetting of top clay liners
- 2017
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Ingår i: Journal of Earth Sciences and Geotechnical Engineering. - : Scientific Press International Limited. - 1792-9040 .- 1792-9660. ; 7:2, s. 45-62
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Tidskriftsartikel (refereegranskat)abstract
- Landfills of hazardous waste like radioactive rest products with low activity, or ashes from incinerated organic waste, need to have top clay liners for minimizing penetration and percolation of precipitated rain and meltwater. Temperature and dry weather vary interchangeably with wet periods making the clay desiccate and fissure, and subsequently wetted etc. Top liners are commonly made of smectite clay, which is the best isolating soil material, undergoing swelling and shrinkage to an extent that depends on the clay content and density. The most important question is whether such liners, in unfrozen condition and covered by erosionresisting coarse soil, maintain their coherence and tightness after centuries of hydration/dehydration cycles. The present study, made on physically confined soft Iraqi clay with about 30% smectite indicates that initially homogeneous dense clay shrinks and desiccates and becomes fissured at 30oC and room RH, but partly recovers by becoming water saturated by infiltrated water. A limited number of drying and wetting sequences seem to give approximately the same change, suggesting that, under common weather conditions and lack of external disturbance, such liners retain a considerable part of their initial water tightness. Thick liners with moderately to high density and exposed to loading by overlying coarse fill are expected to serve particularly well.
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| 3. |
- 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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| 4. |
- Dury, Robin, 1994-, et al.
(författare)
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Progressive Landslide Analysis with Bernander Finite Difference Method
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The poster presents a new Spreadsheet developed by Robin Dury (2017) to simplify the use of the Finite Difference Method developed by Stig Bernander et al (2011, 2016).It includes:- Material Properties- Finite Difference Method- Progressive failure process with five phses- Discussion- References
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| 5. |
- Hatem, Mohammed, et al.
(författare)
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Design of concrete mixes by systematic steps and ANN
- 2012
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Ingår i: Journal of Advanced Science and Engineering Research. - 2231-8844. ; 2:4, s. 232-251
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Tidskriftsartikel (refereegranskat)abstract
- The current research caters for the possibility of arriving at a system for designing concrete mixeseasily using available materials locally by specified wide ranges of pre-requisites of three mainprescribed properties to cover a good variety of practical mixes, which are water, water-cement ratioand total aggregate-cement ratio. Using these three properties, a tri-linear form was constructed bygraphical technique manner based on absolute volume approach. This approach defines as asummation of absolute volume for each of these three materials individually water, cement andaggregate should be equal to the absolute volume of whole concrete mixture based on thesealtogether. A quad-form area which includes a wide range of mixes can be formed from thisrepresentation. This area should achieve all the prescribed properties aforementioned. Artificial neuralnetwork concept used in this study also to build easily and quickly system which can be translatedinto Excel sheet. This system predict proportions of concrete mixture and the compressive strengthusing the results designed by the quad-form area method in addition to the data from literature around500 mixes based on local materials used in Iraq. Six input parameters (water to cement ratio, theslump, % of fine to total aggregate content, maximum aggregate size, fineness modulus of fineaggregate and the compressive strength) were used in this system to get the outputs. In addition, nineinput parameters ((water, cement, sand and gravel contents) and the properties of the mix (Finenessmodulus, W/C ratio, the slump, % of fine to total aggregate and the M.A.S)) were used as basis ofcompressive strength model. The algorithm of this system aimed to reduce the high number of trailmixes error as well as saving the labors, cost and time. Results indicated that the concrete mix designand the compressive strength model can be predicted accurately by using graphical perspective andthe ANN approach.
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| 6. |
- Hatem, Mohammed, et al.
(författare)
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Interaction of clay and concrete relevant to the deep disposal of high-level radioactive waste
- 2015
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Ingår i: Applied Clay Science. - : Elsevier BV. - 0169-1317 .- 1872-9053. ; 118, s. 178-187
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Tidskriftsartikel (refereegranskat)abstract
- A concept for the disposal of highly radioactive waste at depth in the Earth’s crust using very deep bore-holes requires that the upper 2 km’s of the 800 mm diameter, steeply drilled holes, be effectively sealed. This can be achieved by using dense smectitic clay where the rock is weakly fractured and strengthening with concrete when fracture zones are encountered. Earlier investigations have shown that chemical reactions between the clay and concrete can be expected both in the upper part where the temperature is lower than 90oC and in the deeper section where the temperature reaches up to 150oC. To study further this interaction, hydrothermal experiments were conducted using mixed-layer (illite/smectite) Holmehus clay and a low pH slag-based concrete placed in contact under isothermal conditions at 21°C, 100oC and 150oC for a period of 8 weeks. The sample sets, which consisted of two clay discs separated by concrete cast on the lower clay disc, were extracted in undisturbed form and exposed to uniaxial pressure for measuring the compressive strength at successively increasing pressures. Compression tests underenhanced thermal conditions led to strengthening of both the clay and concrete. X-ray diffraction and electron microscopy analysis of the material revealed an increasing degree of cation exchange at higher temperatures with the cement, whereby Ca replaced Na in the interlayer sites of smectite layers. Dissolution of illite/smectite was also evident occurring at enhanced temperatures, with a decrease in K, Mg and Fe content with advanced alteration. The enhanced strength of clay can be partly attributed to the precipitation of cement phases from circulating fluids, including precipitation of gypsum.
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| 7. |
- Hatem, Mohammed, et al.
(författare)
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Packing theory for natural and crushed aggregate to obtain the best mix of aggregate : research and development
- 2012
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Ingår i: Proceedings of World Academy of Science, Engineering and Technology. - 2010-376X .- 2070-3740. ; 6:7, s. 479-485
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Tidskriftsartikel (refereegranskat)abstract
- Concrete performance is strongly affected by the particle packing degree since it determines the distribution of the cementitious component and the interaction of mineral particles. By using packing theory designers will be able to select optimal aggregate materials for preparing concrete with low cement content, which is beneficial from the point of cost. Optimum particle packing implies minimizing porosity and thereby reducing the amount of cement paste needed to fill the voids between the aggregate particles, taking also the rheology of the concrete into consideration. For reaching good fluidity superplasticizers are required. The results from pilot tests at Luleå University of Technology (LTU) show various forms of the proposed theoretical models, and the empirical approach taken in the study seems to provide a safer basis for developing new, improved packing models.
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| 8. |
- Hatem, Mohammed, et al.
(författare)
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Performance of Cement-poor Concrete with Different Superplasticizers
- 2014
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Ingår i: International Journal of Research and Reviews in Applied Sciences. - 2076-734X .- 2076-7366. ; 18:2, s. 163-172
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Tidskriftsartikel (refereegranskat)abstract
- Concrete can be used for casting plugs in deep boreholes where fracture zones are intersected. They will be exposed to flowing groundwater and be in contact with very tight seals of smectite clay installed where the surrounding rock is tight. The cast concrete must be able to carry the clay segments placed over it after a few days. Its bearing capacity does not have to be very high after that since the clay soon adheres to the rock and carries itself. The concrete must be poor in cement for minimizing the risk of creation of voids caused by dissolution of the cement and it should have “inert” aggregate of quartz-rich material. Inorganic superplasticizers instead of conventional organic ones should be used for eliminating the risk of degradation and loss by formation of colloids that can carry radionuclides to the biosphere from holes bored in repository rock. The two concrete types discussed in the present study had Portland and Merit 5000 low pH cement as binders and crushed quartzite as aggregate. Talc mineral powder and ordinary organic Glenium 51 were used as superplasticizers for comparing their impact on the physical properties. The matrix of the cement-poor talc concrete gave ductile behaviour during initial hardening. The very dense matrix of either of the concretes would not lead to compression of the system even after complete loss of cement, which will happen over a longer period of time. The overall conclusion was that talc as superplasticizer and conditioner of the concrete can make the concrete sufficiently fluid for constructing seals at depth in boreholes, and react with cement to provide high strength with some delay. pH is much lower in Merit than in Portland concrete, which causes less impact on the clay seals. Portland concrete has five times higher strength than Merit concrete after a week but three times lower strength after 28 days.
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| 9. |
- Hatem, Mohammed, et al.
(författare)
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Proportioning of cement-based grout for sealing fractured rock-use of packing models
- 2013
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Ingår i: Engineering. - : Scientific Research Publishing, Inc.. - 1947-3931 .- 1947-394X. ; 5:10, s. 765-774
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Tidskriftsartikel (refereegranskat)abstract
- Fractured, very permeable rock hosting repositories for radioactive waste will require grouting. New grout types of possible use where long-term performance is needed should have a small amount of cement for minimizing the increase in porosity that will follow from the ultimate dissolution and erosion of this component. They have to be low-viscous and gain strength early after injection and packing theory can assist designers in selecting suitable proportions of various grout components. Optimum particle packing means that the porosity is at minimum and that the amount of cement paste needed to fill the voids between aggregate particles is very small. Low porosity and microstructural stability must be guaranteed for long periods of time. Organic additives for reaching high fluidity cannot be used since they can give off colloids that carry released radionuclides and talc can be an alternative superplasticizer. Low-pH cement reacts with talc to give high strength with time while Portland cement gives early but limited strengthening. The clay mineral palygorskite can be used for early gelation because of its thixotropic properties. Once forced into the rock fractures or channels in soil it stiffens and serves as a filter that prevents fine particles to migrate through it be lost. However, its hydrophilic potential is too high to give the grout a high density and high strength. According to the experiments carried out most of the investigated grouts are injectable in fractures with apertures down to 100 μm.
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| 10. |
- 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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