Dissertations / Theses: 'Granular materials'

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Higgins, Anthony. "The dynamics of granular materials." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.259539.

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Rege, Nabha V. (Nabha Vithal). "Computational modeling of granular materials." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10844.

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Grinev, Dmitri. "Statistical mechanics of granular materials." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621514.

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Isert, Nathan. "Dynamics of levitated granular materials." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:352-opus-27683.

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Hostler, Stephen Richard Brennen Christopher E. "Wave propagation in granular materials /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-02072005-120514.

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Paine, A. C. "Elastic properties of granular materials." Thesis, University of Bath, 1998. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.245957.

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Holladay, Seth R. "Optimized Simulation of Granular Materials." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3856.

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Visual effects for film and animation often require simulated granular materials, such as sand, wheat, or dirt, to meet a director's needs. Simulating granular materials can be time consuming, in both computation and labor, as these particulate materials have complex behavior and an enormous amount of small-scale detail. Furthermore, a single cubic meter of granular material, where each grain is a cubic millimeter, would contain a billion granules, and simulating all such interacting granules would take an impractical amount of time for productions. This calls for a simplified model for granular materials that retains high surface detail and granular behavior yet requires significantly less computational time. Our proposed method simulates a minimal number of individual granules while retaining particulate detail on the surface by supporting surface particles with simplified interior granular models. We introduce a multi-state model where, depending on the material state of the interior granules, we replace interior granules with a simplified simulation model for the state they are in and automate the transitions between those states. The majority of simulation time can thus be focused on visible portions of the material, reducing the time spent on non-visible portions, while maintaining the appearance and behavior of the mass as a whole.

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Padbidri, Jagan Mohan. "A network-cell based framework for multiscale analysis of granular materials." Pullman, Wash. : Washington State University, 2010. http://www.dissertations.wsu.edu/Dissertations/Spring2010/j_padbidri_041510.pdf.

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Lakku, Pavan Misra Anil. "Anisotropic granular models for cohesive materials." Diss., UMK access, 2005.

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Thesis (M.S.)--School of Computing and Engineering. University of Missouri--Kansas City, 2005. "A thesis in civil engineering." Typescript. Advisor: Anil Misra. Vita. Title from "catalog record" of the print edition Description based on contents viewed March 12, 2007. Includes bibliographical references (leaves 75-77). Online version of the print edition.

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Fleming, Paul R. "Impact assessment of layered granular materials." Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/27822.

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Granular materials utilised in the construction of highway foundation layers are currently specified on the basis of index tests. As a consequence, the material acceptability criteria, although developed from many years' experience, do not directly measure a fundamental performance parameter. Once the granular materials are placed and compacted they are rarely checked and as such no assurance can be given to their likely engineering performance in situ. An important performance parameter, the stiffness modulus, describes the ability of the constructed layer(s) to spread the construction (and in-service) vehicle contact pressures and reduce the stresses, and hence strains, transmitted to the lower weaker layers. A significant improvement upon current practice would be to include the specification of 'end product' testing and to include the direct measurement in situ of stiffness modulus to assure performance. A prerequisite of this is suitable site equipment to measure such a parameter, and a sound basis upon which to interpret and utilise such data. Tests do exist that measure stiffness modulus in situ, although in general they measure a 'composite' stiffness, i.e. a single transducer infers the surface strain, under controlled loading, for the construction as a whole and the region affecting the measurement is not precisely known. Currently then, no routine portable device exists for the direct stiffness modulus assessment of the near surface or last layer applied. This would not only provide for consistency of construction, but avoid burying poor or weaker layers. This thesis describes the evaluation of a portable impact test device and research into the behaviour of granular soils subject to rapid transient loads. The requirements for the assessment of pavement granular foundation layers are reviewed, followed by a critical appraisal of current devices that measure the stiffness modulus of material in situ. The prototype impact device, known as ODIN, comprising an accelerometer instrumented swinging hammer, is described. A selection of field data, demonstrating the primary soil influencing factors and correlations with other devices, is presented. Controlled laboratory testing is also described, comprising impact testing with free-falling masses in addition to the ODIN device and for tests on foundations instrumented with pressure cells, that further explains the dynamic behaviour of the material under test. Problems with both hardware and software, associated with high-frequency impact testing are highlighted. In particular, the restraint of the impact mass by the swinging arm mechanical component is observed to lead to a proportion of the impact energy being channelled back into the apparatus during a test. The channelled energy is shown to produce resonance of the apparatus, which in turn leads to problems in interpretation of the accelerometer signal. Numerical methods are then explored and it is demonstrated that the predictions approximated well to the free-falling weights experimental data. Discussion of the research findings concludes with a model for soil behaviour under impact testing, requirements for an improved impact device and the further research work required to realise the potential of such equipment.

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Fraige, Feras. "Distinct element simulation of granular materials." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433993.

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Diaz, BegonÌƒa Ruiz. "Magnetic properties of granular magnetic materials." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428429.

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Mahmoud, M. A. "Continuously penetrating bodies in granular materials." Thesis, University of Southampton, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356027.

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Chilukwa, Nathan Ntanda. "Vibratory hammer compaction of granular materials." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80132.

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Thesis (MScEng)--Stellenbosch University, 2013. ENGLISH ABSTRACT: Compaction is one of the key processes in the construction of road pavement layers. Not only is it significant in ensuring the structural integrity of the material in the road layers, but it also has an influence on the engineering properties and performance of the soil material. A poorly compacted material is characterised by low density, high porosity and below standard shear strength. This, as a result causes rutting, moisture susceptibility, potholing, corrugations and passability problems on the road. Therefore, it is vitally important that field compaction is done correctly. For this reason, laboratory compaction methods have been developed to simulate the field compaction process in the laboratory. The Mod AASHTO test has long been used as the laboratory compaction method of choice by virtue of its simplicity and the lack of bulky equipment required. However, previous studies have established that the Modified AASHTO method does not adequately simulate field compaction criteria especially for cohesionless materials. Two reasons have been advanced; The Mod AASHTO compaction method does not adequately simulate the compaction done in the field when the granular mix is laid; The compaction method may cause disintegration of the material. Alternative tests have been considered and much research has focused upon the use of a modified demolition hammer (vibratory hammer) for laboratory compaction of granular materials. This study undertook to evaluate the influence of test factors pertinent to the vibratory hammer compaction method. The influence of these test factors on compaction time and obtainable material density was assessed with the objective of developing a compaction method for granular materials. Vibratory hammer compaction tests were conducted on G3 hornfels, G4 hornfels and G7 sandstone material types and to a lesser extent, reclaimed asphalt (RA). Densities obtained were referenced to Mod AASHTO compaction density. Findings of the study showed that, the mass of the tamping foot has a significant influence on the obtainable compaction density. Other factors such as, moisture content, frequency and frame rigidity were also found to affect compaction with the vibratory hammer. In addition, it is shown that the surcharge load does not significantly influence the obtainable compaction density but does contribute to the confinement of the material and restricts the upward bounce of the hammer. On the basis of the results and findings, a compaction method was proposed, incorporating test parameters and factors that would provide ideal results for a set compaction time. Repeatability tests showed that, the developed vibratory hammer compaction method was effective in compacting graded crushed stone material types (i.e. G3 and G4) and probably RA. The test was not as effective on the G7 material. Further studies on this material (G7) are required. In addition to the previous testing regime, a comparative assessment of the developed vibratory hammer compaction method in relation to the vibratory table method was done. The results show that the vibratory hammer is capable of producing specimens of densities comparable to those of the vibratory table. A sieve analysis undertaken before and after compaction showed that compaction with the developed vibratory hammer compaction method does not result in any significant material disintegration. Based on the results of this study, a specification for the determination of maximum dry density and optimum moisture content of granular material using the vibratory hammer is recommended. AFRIKAANSE OPSOMMING: Kompaksie is een van die belangrikste prosesse in die konstruksie van die padplaveisel. Dit is nie net waardevol vir die versekering van strukturele integriteit van die materiaal, maar dit het ook 'n invloed op die ingenieurseienskappe en vermoë van die grond materiaal. 'n Swak gekompakteerde materiaal word gekenmerk deur 'n laë digtheid, hoë porositeit, on onvoldoende skuifweerstand. Die kenmerke maak die material vatbaar vir vogen. Lei tot spoorvorming, slaggate, golwe en deurgangs probleme op die pad. Dit is dus uiters noodsaaklik dat veld kompaksie korrek gedoen word. Om hierdie rede, is kompaksie metodes in die laboratorium ontwikkel om sodaend veldkompaksie te simuleer. Die “Mod AASHTO” laboratorium kompaksie toets is die gekose laboratorium kompaksie metode op grond van sy eenvoudigheid en gebruik van minimale toerusting. Vorige studies het egter bevestig dat die “Mod AASHTO”-metode nie veldkompaksie akkuraat kan simuleer nie, veral vir kohesielose materiaal. As gevolg van twee hoofredes; Die Mod AASHTO kompaksiemetode is nie ‘n realistiese en vergelykende simmulering van kompaksie soos dit in die veld gedoen word nie; Die kompaksie metode mag verbrokkeling van die materiaal veroorsaak. Alternatiewe toetse was oorweeg en baie navorsing het gefokus op die gebruik van 'n aangepaste vibrerende hamer. Hierdie studie het onderneem om verskeie relevante toetsfaktore van die vibrerende hamer en hul invloed op die kompaksie en verkrygbare digtheid te bestudeer. Die invloed van hierdie toetsfaktore op kompaksietyd en verkrygbare materiaal digtheid was geassesseer met die doel om 'n kompaksiemetode vir granulêre materiaal te ontwikkel. Vibrerende hammer kompaksietoetse was uitgevoer op G3 hornfels, G4 hornfels en G7 sandsteen materiaal en tot 'n mindere mate herwinde asfalt. Digthede verkry was verwys na die Mod AASHTO kompaksie digtheid. Resultate van die studie het getoon dat die gewig van die stamp voet ‘n merkwaardige invloed het op die verkrygbare kompaksie digtheid. Ander faktore soos voginhoud, frekwensie en raam styfheid het ook getoon om kompaksiedigtheid te beïnvloed met die vibrerende hammer. Benewens was ook getoon dat die toeslaglading geen beduidende invloed het op die verkrygbare kompaksie digtheid nie, maar wel bydrae tot die inperking van die materiaal en verhoed die vertikale terugslag van die hammer. Gebaseer op die resultate en bevindinge was ‘n kompaksiemetode voorgestel wat toets parameters integreer met toetsfaktore en tot volg ideale resultate vir ‘n gegewe kompaksietyd voorsien. Herhaalde kalibrasie toetse het getoon dat die ontwikkelde kompaksiemetode effektief is in die kompaktering van gegradeerde gebreekte klip materiaaltipes (G3 en G4) en moontlik herwanne asfalt. Die toets was nie so doeltreffend op die G7 materiaal nie. Verdere studies op hierdie materiaal (G7) is dus nodig. Addisioneel tot die vorige toets, is bevind dat ‘n vergelykende assesering van die ontwikkelde vibrerende hammer kompaksiemetode in verhouding tot die vibrerende tafel. Die resultate wys dat die vibrerende hammer die vermoë het om toetsmonsters met digthede vergelykbaar met die vibrerende tafel te produseer. Sifanalise voor en na kompaksie het getoon dat verdigting met die ontwikkelde vibrerende hamer kompaksie metode nie lei tot die disintegrasie van die materiaal nie. Gebasseer op die resultate van dié studie was ‘n spesifikasie vir die bepaling van maksimum droé digtheid en optimale voginhoud van granulêre material aangeraai.

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Nixon, Stuart A. "Yield functions suitable for granular materials." Thesis, University of Aberdeen, 1999. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU122515.

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The behaviour of granular materials is complex. Unlike all other engineering materials their volume change does not only depend upon an applied mean stress, but also on the change in shape of the body. This complexity in the behaviour makes it difficult to develop useful constitutive equations which describe the behaviour. Many constitutive models exist for granular materials. Using an established approach new models, suitable for simulating small cyclic strains, are presented within this thesis. The basis for these models is a new dilatancy rule. By setting the volume strain proportional to the square of the shear strain it is possible to develop a yield surface which is characterised by kinematic hardening. All models are developed from an energy balance. In the past this has only been made up of two terms, the work done and the energy dissipated as a result of plastic deformation. Including a term which expresses the rate at which energy is stored during elastic deformation allows the simulation of cyclic shear loading on granular materials. These simulations show pleasing agreement with experimental results. To account for the nonlinear plastic behaviour seen in granular materials, hardening rules for a two dimensional case are developed. These introduce critical states and maximum densities into the formulation. By modelling the results of cyclic shear tests on assemblies of rods, it is shown that the hardening rules are not only useful for modelling soils, but also other materials, such as pastes. Finally a dissipation function which has been suggested by Houlsby is used to formulate a new model. Again this is based on the successful dilatancy rule used in the previous models. By combining the dissipation function of Houlsby and the quadratic dilatancy rule, a yield surface and flow rules are developed which successfully model the circular loading of sands.

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Liu, Alfred D. "Numerical modeling of granular magnetic materials /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9989763.

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Nguyen, Thi Thu Tra. "Dynamic instabilities of model granular materials." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSET007/document.

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Cette thèse étudie les instabilités dynamiques des milieux granulaires modèles saturés à l’aide d’un appareil triaxial classique. Les instabilités englobent la liquéfaction et les effondrements en compression isotrope drainée, les frottements saccadés en compression triaxiale drainée. Ces instabilités apparaissent spontanément à des contraintes effectives de confinement imprévisibles. Elles sont accompagnées de très rapides et très fortes surpressions interstitielles, malgré un drainage approprié; ce que ne présentent pas les milieux granulaires naturels. En compression isotrope drainée (consolidation), des effondrements locaux naissent instantanément. En compression triaxiale drainée, on observe de larges frottements saccadés quasi-périodiques caractérisés par des déformations volumiques et axiales contractantes. De temps en temps, ces effondrements et frottements saccadés locaux peuvent se développer en liquéfaction menant à une destruction complète de la structure granulaire. Les données à haute résolution temporelle issues de ce travail ont permis la découverte d’une nouvelle famille de liquéfaction dynamique et statique. L’étude des émissions acoustiques passives a permis l’identification de signature spectrale caractéristique. Pour les frottements saccadés, la phase de glissement peut être interprétée comme une consolidation dynamique, limitée par l’unique surface en dessous de la ligne critique de rupture dans le plan des contraintes effectives. La séquence temporelle précise des événements exclut que la pression interstitielle soit la cause principale des instabilités. Cependant, le rôle important de la surpression interstitielle est démontré dans des relations quantitatives entre les incréments de contraintes, et de déformations et l’éphémère surpression interstitielle stabilisée développée pendant la phase de glissement. Cela montre finalement la nature quasi-déterministique de ces instabilités dynamiques. Ces relations empiriques sont basées uniquement sur l’amplitude maximale de l’accélération verticale de très courte durée et sont gouvernées indépendamment par la pression de confinement et par l’indice des vides. La similarité de la surpression interstitielle entre différentes instabilités suggère fortement quelques mécanismes similaires de déclenchement, probablement à partir de ré-arrangements de la micro-structure granulaire This thesis reports a laboratory study on the dynamic instabilities of model saturated granular material using a triaxial apparatus. The term instability consists of isotropic collapse and liquefaction under isotropic compression and of stick-slip under triaxial compression in drained condition. The instabilities spontaneously occur at unpredictable effective stress with unexpected buildup of excess pore pressure irrespective of fully drained condition, contrasting with the instability-free behaviour of natural granular materials. In isotropic compression, instantaneous local collapse happens and in triaxial compression, very large and quasi-periodic stick-slip occurs with sudden volumetric compaction and axial contraction. Sometimes, these local failures (collapse and stick-slip) can develop into total liquefaction failure, destroying completely the granular structure. High time-resolved data permit the discovery of a new family of dynamic and static liquefaction. Passive acoustic measurements allow the identification of typical spectral signature. For stick-slip phenomenon, the slip phase with constant duration of stress drop can be interpreted as dynamic consolidation at constant deviatoric stress, limited by a unique boundary inside the critical state line in the effective stress plane. The precise temporal sequence of mechanical measurements excludes the generated pore pressure as the main cause of the instabilities. However, the role of pore pressure is emphasised by consistent quantitative relations between the amplitude of incremental stresses, incremental strains and the ephemeral stabilised excess pore pressure developed during the dynamic event, leading to the quasi-deterministic nature of granular instabilities. These empirical relations are based only on the short-lived maximum vertical acceleration and governed separately by the confining pressure and the initial void ratio. The similarity of pore pressure evolution for different kinds of instability strongly suggests some common speculative triggering mechanisms, probably originated from different rearrangements of the granular micro-structure

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Sharrock, Glenn. "Tool shearing of granular media /." St. Lucia, Qld, 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17559.pdf.

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Magnusson, Simon. "Environmental Perspectives on Urban Material Stocks used in Construction : Granular Materials." Licentiate thesis, Luleå tekniska universitet, Geoteknologi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-60305.

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The peoples demand of functions and services in cities is the driver for energy and material flows. Most people in the world are now living in urban areas. In order to achieve a sustainable development of cities, both resource use and environmental impact have to be reduced. For construction activities, an important aspect is to increase the reuse of construction materials. From a resource perspective, the urban demand for construction of buildings, infrastructure and other facilities results in materials accumulated in constructions but also in other applications and in landfills. The materials can be described as the urban material stock where some materials are used and others are not used, i.e. wasted. There are many cases where material stocks are used for construction purposes. For example, used concrete and bricks, excavated soil and rock from construction projects and other wasted materials such as rubber from tires can be crushed, shredded and sorted to granules and used in many different construction applications. Different perspectives can be applied when assessing the environmental impacts of using stocked material in construction. The overall aim of this thesis is to study the environmental impacts of using granular soil, rock and rubber in construction. For soil and rock, the aim is to study the environmental impact of material management in urban areas. For granular rubber, the aim is to study the environmental impact of artificial turf from a life cycle perspective and from different infill materials of recycled and new rubber and plastics. The literature of excavated soil and rock was reviewed in order to identify and quantify the material flows and greenhouse gas (GHG) emissions from the management of soil and rock materials. For artificial turf and the different infill materials, a life cycle approach was used to quantify the energy use and GHG emissions. A chemical analysis of potential chemical leaching from the different infill materials to water was conducted in order to compare potential local emissions to water. Based on the results, it was concluded that the knowledge about the urban flows of excavated soil and rock is lacking in terms of patterns, quantities, qualities and its environmental performance. A resource perspective is missing in the literature. However, the recycling of soil and rock can reduce resource use and GHG emissions. It was suggested that models are developed that take into account future material demand and availability to soils and rock. From such information it would be able to assess sustainable management practices and the possibilities of sharing materials between urban construction projects in order to reduce resource use and environmental impact. It was concluded that for the life cycle of artificial turf, the production of construction materials contributes largely to energy use and GHG emissions. Differences in terms of energy use and GHG emissions for the production of infill materials are large. The production of new material required more energy and resulted in more GHG emissions than using recycled rubber. The potential release of substances from infill materials to water were shown to be possible for all infill materials analyzed. Previous assessments of local environmental impacts of using infills generally concludes that the impacts are small. These assessments are primarily focused on infill of recycled tires. It is therefore concluded that environmental assessments of local impact should include all infill types. Environmental assessments of using stocked materials in construction should take into consideration the material applications´ significance for the environmental impacts at a higher system level. Broader system boundaries in environmental assessments will reduce the risk for sub-optimizations when taking decisions on how materials should be used in construction.

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Lee, Seunghun Marghitu Dan B. "Impacts of kinematic links with a granular material." Auburn, Ala., 2009. http://hdl.handle.net/10415/1751.

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Wijewickreme, Dharmapriya. "Constant volume friction angle of granular materials." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26342.

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The postulate that the constant volume friction angle Φ[sub cv] of a granular material is unique is verified experimentally. The constant volume friction angle of a wide spectrum of granular granular materials is measured using the ring shear device, enabling the material to be sheared to large, in fact unlimited strains at which 0cv is mobilized. Granular materials tested were composed of particles ranging from minerals to metals. The effects of confining pressure, initial packing density, particle size, gradation and particle shape on the value of Φ[sub cv] are studied. The possible influence of the presence of pore water is also investigated. The test results indicate that for a given material, Φ[sub cv] is independent of confining pressure, initial packing density and particle size. Neither particle crushing nor change in shape of the particle had any noticeable effect on the observed value of Φ[sub cv]. These experimental results suggest that the constant volume friction angle is a fundamental property of a granular material which is dependent only on the mineral constituency of the material. A comparison of Φ[sub cv] and the friction angle mobilized at the point of maximum contraction in drained shear (a transient constant volume state) as well as the friction angle mobilized at phase transformation state in undrained shear (a transient constant pore pressure state) is also made, in an attempt to seek a broader fundamental significance of Φ[sub cv]. Applied Science, Faculty of Civil Engineering, Department of Graduate

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Hui, Pak-Ming. "Topics in the physics of granular materials /." The Ohio State University, 1987. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487332636473225.

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Hossain, MD Tanvir. "Mobility in granular materials upon dynamic loading." Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/22976.

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This Thesis explores the mechanisms controlling the mobility of large objects embedded in granular materials. The goal is to establish which loading conditions lead to their motion and to identify the underlying physical mechanisms. To this aim, laboratory experiments were conducted using a canonical mobility test, which involves uplifting a plate embedded in a dry granular packing vertically. The experimental conditions were varied in order to evidence the effect of the presence of water in the granular packing, and the effect of dynamic loadings whereby the plate is moved at different velocities or subjected to a cyclic force. Three main discoveries emerged from these experiments. The first discovery is the development of a drag force instability when the plate is driven at a constant and slow velocity, which vanishes at higher velocities. The second discovery is a visco-elastic dynamics developing in immersed packing, which is evidenced by drag force relaxation dynamic and a velocity-driven increase in drag force. The third discovery is a drop in packing resistance when the plate is subjected to a low magnitude cyclic force. The physical origin of these mobility responses is consistently analysed and rationalised, considering elementary mechanical processes. The conclusions of this Thesis form a fundamental basis to advance a variety of engineering discipline pertaining to foundation design, excavation techniques and bulk material handling.

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Zhai, Chongpu. "Stress-dependent electrical conduction in granular materials." Thesis, The University of Sydney, 2017. http://hdl.handle.net/2123/17975.

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This dissertation is focused on electrical conduction behaviour in granular systems with the purpose of acquiring a fundamental understanding towards applications of granular materials. Performance in a range of engineering systems can be largely influenced by complex multi-physics interactions arising from microstructures of granular materials. The bulk of this dissertation is built on six published or submitted papers. After project background and related previous work introduced in Chapters 1 and 2, respectively, Chapters 3 and 4 deal primarily with the contact properties between rough surfaces. The obtained information at the interfacial scale serves as an experimental and numerical basis for modelling inter-particle contacts in granular media. Chapter 5 with the fifth paper presents the effects of network configuration on macroscopic network responses focussing on the dielectric universal scaling behaviour. In Chapter 6, the final paper shows a physical picture illustrating experimentally observed alternating-current universal scaling in conductive granular systems under different stress states. An effective numerical approach incorporating inter-particle interaction has been provided to simulate electrical responses of granular materials. The combination of the studies from macro-scale phenomena, network topologies, and inter-particle properties is presented leading to new physics-based constitutive models that contain lower scale information. This dissertation presents a new comprehensive understanding of conduction behaviour in granular materials by means of a physics-based framework combining features containing both experimental and numerical information obtained across various length scales, guiding design and optimisation of various granular materials.

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Dai, Beibing, and 戴北冰. "Micromechanical investigation of the behavior of granular materials." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B45700680.

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Dierichs, Karola [Verfasser], and Achim [Akademischer Betreuer] Menges. "Granular architectures : granular materials as "designer matter" in architecture / Karola Dierichs ; Betreuer: Achim Menges." Stuttgart : Universitätsbibliothek der Universität Stuttgart, 2020. http://d-nb.info/1205736948/34.

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Bowman, Elisabeth Therese. "The ageing and creep of dense granular materials." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/251841.

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Dawson, Janet Caroline. "The electronic properties of granular and amorphous materials." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318097.

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Kamal, Mumtaz Ahmed. "Behaviour of granular materials used in flexible pavements." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333824.

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Lambert, John Peter. "Novel assessment test for granular road foundation materials." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/3099.

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Drivers for sustainability have made it necessary for the construction industry to adapt its traditional processes to become both more efficient and produce less waste. Performance based design and specification in the UK for motorways and trunk roads permits a very flexible approach to pavement design, material selection and performance related testing aimed at utilising materials to their maximum potential. However, it is clear that within the emerging philosophy of using materials that are 'fit for purpose' there are many technical challenges for design and specification. There is a need to develop suitable methods of evaluating materials prior to their being used on site. This project was born out of this requirement, with a particular emphasis on coarse granular materials due to their common role in capping construction and also their unique difficulty for measurement under laboratory conditions due to their large range of particle size. A novel assessment test for coarse capping materials for roads that can be used to indicate their likely short-term in situ performance, under controlled laboratory conditions before construction on site, has been developed during this research programme. Key findings relating to the behaviour of coarse capping materials, the use of stiffness measuring devices and variables that influence the measurement of composite stiffness are discussed in detail. The research highlights the necessity for adequate drainage and protection of foundation materials against increase in water content. When adopting a performance specification the timing of the pavement assessment is critical, both on site and in the laboratory. The performance measured on site should perhaps only be considered as a 'snapshot' relating to the stress state in the material at the time of testing.

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Karlsson, Tomas. "Finite element simulation of flow in granular materials." Licentiate thesis, Luleå tekniska universitet, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26139.

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Lopatina, Lena M. "Statistical Mechanics of Nanoparticle Suspensions and Granular Materials." Kent State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=kent1310414818.

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Jiang, Sheng. "Fracture and Fragmentation of Granular Materials Under Impact." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/20250.

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Fracturing plays an important role in controlling the compaction behaviour of granular materials under impact. Associated effects include changes to porosity and permeability, especially along earthquake faults, and during mining and petroleum production processes. The overarching objective of this thesis is to understand the intrinsic fracture mechanisms of both pure brittle granular materials and cemented granular materials. Fracture mechanisms are quantitatively analysed in terms of energy dissipation during high speed grain fracture and fragmentation process. Furthermore, the effects of both inter-grain contact material and cement material on the fracture mechanisms are investigated at microscopic level. High strain rate experiments demonstrate that only a small portion of the input stress wave energy is dissipated through the fragmentation of the grain chain system. Micro-CT results validate that the fracture energy only accounts for a small portion of the chain system’s absorbed energy, even after including the undetected surface area of the micro-cracks. Comparisons between the glass bead chain systems, with and without contact materials, clearly indicate that the contact material changes the chain damage patterns. The contact material alters the initial contact state of the shielded grains and consequently restrains the initiation of cracks, governed by tensile stresses near the contact surface. However, different fracture mechanisms, namely, cement-focused and grain-focused fracture mechanisms can be activated for different cement materials covering a single glass bead, which is dependent on the cement/grain interface adhesion. Using measuring techniques based on Fourier transform, the locality of damage within the cemented bead is quantitatively analysed, as well as their preferential crack orientation. Several sporadic curved cracks come under observation near the interface region in the cement-focused fracture case, roughly along the cement/grain interface. By contrast, for the grain-focused fracture case, fracture is most likely to occur along the central loading axis area of the cemented bead and prevailingly forms diametric cracks along the impact direction.

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Tengattini, Alessandro. "A micro-mechanical study of cemented granular materials." Thesis, The University of Sydney, 2015. http://hdl.handle.net/2123/13973.

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Cemented Granular Materials (CGMs) are ubiquitous in nature. Their behaviour is driven by phenomena occurring at the scale of individual grains and cement bonds. However, the effect of this scale on the engineering response has lacked a systematic description and is rarely acknowledged in the models portraying their behaviour. This dissertation contributes to the development of a methodological framework for CGMs, relating the behaviour of individual grains to their collective response at the macroscopic scale, through a combination of analytical, experimental and numerical approaches. Analytically, a novel constitutive model for CGMs is developed, which adopts measurable internal variables describing the evolution of key grain-scale processes. This model can successfully predict stress-strain responses as well as the onset and development of localisation patterns for a wide range of pressure regimes. Its constitutive parameters have a precise physical meaning and are directly quantifiable. Experimentally, a triaxial testing program is carried out on specimens of CGMs while acquiring x-ray tomographic images at a resolution sufficient to discern individual grains and cement bonds. A toolset is developed to characterise, for the first time, each grain and cement bridge in the specimen, their evolution, and to extract statistically representative measures of the grain-scale processes. Numerically, boundary value problems are solved using the finite element method to bridge experimental observations to analytical predictions, and vice versa, while accounting for the effects of strain localisation. The acknowledgement of grain-scale behaviour within this methodological framework allows for a realistic validation of the constitutive models not only at the scale of the specimen response and its localisation features, but also at the scale of individual grains. This is pivotal in several open engineering problems controlled by the localised evolution of the micro-structure.

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Darabi, Babak. "Dissipation of vibration energy using viscoelastic granular materials." Thesis, University of Sheffield, 2013. http://etheses.whiterose.ac.uk/3929/.

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This work addresses the way in which a viscoelastic granular medium dissipates vibration energy over broad ranges of frequency, amplitude and direction of excitation. The viscoelastic properties (modulus and loss factor) of polymer particles are obtained experimentally both by deriving the master curve of the material and by measuring the stiffness of these spherical particles at different frequencies using a test rig designed for this purpose. Three dimensional Discrete Element Method (DEM) is used to develop a numerical model of the granular medium and is validated by comparison with experimental results. Despite the simplifications the model was found to be in good agreement with experiments under vertical and horizontal vibrations with different numbers of particles over a range of frequencies and amplitudes of excitation. The study is extended to investigate different phases that occur under vibrations of granular materials. The low amplitude vibrations when the particles are permanently in contact without rolling on each other is called solid phase. In this phase, most energy is dissipated internally in the material. A theoretical/numerical approach is considered for this phase and it is validated by experiment. At higher amplitude vibrations when the particles start to move and roll on each other (the convection phase) there is a trade-off between energy dissipation by friction and viscous/viscoelastic effects. Energy dissipation is relatively insensitive to the damping of individual particles. At extremely high amplitude vibrations particles spend more time out of contact with each other (the particles are separated from each other – gas region). It can be seen the particles with lower damping reach the gas region earlier because they are less sticky and more collisions can happen so although the damping for each individual particle it less, the total damping increases. ii The effect of parameters of particles on energy dissipation is also studied using sensitivity analysis. The benefit of doing this is to better understand how each parameter influences the total system damping.

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CHIEREGATO, ALESSIO. "Permeation grouting of granular soils by innovative materials." Doctoral thesis, Politecnico di Torino, 2015. http://hdl.handle.net/11583/2601354.

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The injection technique based on cement mixtures had a constant evolution since its first application in 1802 by Bérigny for the rehabilitation of masonry diving. Later it was implemented in France and England in the mid-1800s, but by the twentieth century it has started to spread and to globalize the method for applications related to the ground treatment. Initially it was used for the construction of hydraulic works mainly by injecting unstable cement suspensions, with which they could only deal fissured rocks and were therefore excluded granular soils. Then techniques moved to stable cement mixtures and finally to chemical solutions. These technologies have been widely used in the construction of underground structures for roads, subways, as well as for the construction of underground structures in the proximity of existing buildings, where it is necessary the treatment of the soil in order to obtain an improvement of the mechanical and hydraulic characteristics of themselves. Nowadays, the research and experimentation are oriented towards innovative materials so as to broaden the application fields, in order to increase the penetration, and the achievement of high mechanical strength. This thesis has focused on performing injection tests on various soils with different characteristics. In the tests was set as a target, the study of two new materials such as colloidal nanosilica and microcements, through their characterization, their behavior during permeation in granular soils and consolidation that these materials can get. The application of these mixtures depends on several external parameters which vary from the characteristics of the soil, up to the used techniques of injection; for this reason, even today the fields of application are not well defined. The tests carried out in the laboratory of Tunnel and Underground Space Center of the Politecnico di Torino, since there is no normative references, was based on procedures designed ex novo, or in some cases, on standards for geotechnical methods and to the concretes, depending of appropriate theoretical and practical considerations.

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Hudson, Shaymus William. "Mechanical characterization of jammable granular systems." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/75850.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2012. This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. Cataloged from student-submitted PDF version of thesis. Includes bibliographical references (p. 36-37). The mode by which a granular material can transition between fluid-like and solid-like states has been often referred to as jamming. The use of this property (via vacuum pressure) for engineering applications has only recently been explored. Several possible applications are presented. However, thorough characterization of mechanical properties and material selection for jammed systems has not been reported. Glass beads of differing size distributions, silica blasting media, sand, and ground coffee were tested under different vacuum pressures in a procedure similar to an unconsolidated-undrained triaxial compression test for soils. Coffee was found to have the highest strength to weight ratio. Literature predictions of the trend between applied pressure and effective Young' modulus was also investigated. by Shaymus William Hudson. S.B.

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Morris, Billy Ray. "Grain size estimation in anisotropic materials." Thesis, Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/20042.

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Gu, Xiaoqiang, and 顾晓强. "Dynamic properties of granular materials at the macro and microscales." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B47752622.

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Dynamic properties of soil, including modulus and damping, play essential roles in evaluating the response of the soil deposit and its supporting structures when subjected to dynamic loads induced by earthquakes, traffic, explosions, machine foundations, and so on. It is well recognized that the dynamic properties of soil are affected by many factors, such as strain amplitude, stress condition, void ratio, saturation and gradation. Despite tremendous works have been done, the macroscopic effects of several key factors on the dynamic properties of granular material are not yet fully understood, due primarily to its particulate and multiphase nature. Furthermore, the understanding of how the influencing factors affect the dynamic properties of granular material or the underlying fundamental mechanism is inadequate. This study thus is carried out to investigate the effects and the underlying mechanisms of these important factors, including strain amplitude, stress condition, void ratio, particle size, saturation, and initial fabric, by means of advanced laboratory tests and numerical simulations. To study the dynamic properties at the macro scale, a series of laboratory tests are carried out in a state-of-art resonant column (RC) apparatus incorporating bender element (BE) and torsional shear (TS). Test materials include artificial glass beads with different sizes, commercially available standard sands and natural completely decomposed granite (CDG). The specimens are prepared at various densities, confined at different pressures, tested both in dry and saturated conditions, and reconstituted by different preparation methods. In particular, the characteristics of wave signals (both S-wave and P-wave) at various conditions and the associated interpretation methods in BE tests are investigated in detail. The results obtained from BE, RC and TS are compared to clarify the potential effect of test method. Moreover, attempts are made to explain the test results from the viewpoint of micromechanics. Numerical simulations using discrete element method (DEM) are performed to study the dynamic properties of granular materials and explore the underlying fundamental mechanism at the micro scale. The simulations indicate that the elastic properties are closely related to the coordination number and the distribution of normal contact forces in the specimen. The effects of initial fabric and induced fabric, which are respectively achieved by different specimen generation methods and the application of anisotropic stress states, are investigated. The anisotropy of the specimen and its evolution during shearing are also studied. The results indicate that the anisotropy is resulted from the spatial distributions of contact force and contact number. The modulus reduction curve and damping curve obtained from the simulations are compared with those from laboratory tests. published_or_final_version Civil Engineering Doctoral Doctor of Philosophy

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46

Li, Xia. "Micro-scale investigation on the quasi-static behavior of granular material /." View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202006%20LI.

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Holyoake, Alexander James. "Rapid granular flows in an inclined chute." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610681.

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Cardona, Florez Jorge Eduar 1984. "Instabilidades de um leito granular submetido a um escoamento turbulento." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265793.

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Orientador: Erick de Moraes Franklin Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica Made available in DSpace on 2018-08-27T18:01:24Z (GMT). No. of bitstreams: 1 CardonaFlorez_JorgeEduar_M.pdf: 8246209 bytes, checksum: 9860a8456aed83e182b9580704940549 (MD5) Previous issue date: 2015 Resumo: Na natureza e na indústria é comum encontrar fluidos em movimento transportando grãos quando escoam sobre superfícies granulares. Por exemplo, na natureza o transporte de areia por rios e mares quando o fluido é um liquido, ou na formação e migração de dunas nos desertos quando o fluido é um gás, são casos bem conhecidos. Na indústria apresenta-se por exemplo, na extração e transporte de petróleo nos oleodutos, assim como em variados processos químico-industriais envol- vidos com sedimentação, ou simplesmente por utilização de matérias-primas impuras. O fenômeno apresenta-se porque o fluido em escoamento transfere parte da quantidade de movimento à superfí- cie granular, e alguns grãos são postos em movimento mantendo contato com o fundo se a força de arrasto devida ao movimento do fluido supera levemente à força de resistência devida ao peso dos grãos. Os grãos em movimento formam uma camada móvel (leito móvel ou bed-load em inglês), tornando-se instável em alguns casos, gerando rugas e/ou dunas que interagem com o escoamento. Na indústria este fenômeno está associado principalmente a problemas de perda de carga, e a tran- sientes de pressão e vazão, quando fluidos misturados com material granular são transportados por dutos. O presente trabalho faz um estudo experimental da formação e migração deste tipo de ins- tabilidades quando escoamentos turbulentos de água a diferentes velocidades são impostos sobre leitos granulares inicialmente planos de diferentes granulometrias. Os experimentos foram feitos em um canal retangular de material transparente. A evolução do leito foi filmada por uma câmera de alta definição. O comprimento de onda e a celeridade de rugas formadas foram determinados mediante o desenvolvimento de um código numérico em Matlab, utilizado para o tratamento au- tomático das imagens obtidas nos experimentos. Os resultados são comparados com os de outros trabalhos publicados na literatura Abstract: In nature and industry, it is common to find moving fluids carrying grains, when they flow over granular surfaces. For instance, in nature it can be found in the sand transported by rivers and ocean currents, or on the formation and migration of sand dunes in deserts by air; and in industry, it is common to find them in the extraction and transport of oil through pipelines, as well as in several chemical processes involving granular material. This phenomenon arises because part of the momentum is transferred from the fluid flow to the granular surface. Therefore, if the drag force, resulting from the movement of the fluid, exceeds slightly the resistance force occasioned by the weight of the grains, some of these particles are set in motion keeping in touch with the bottom. Consequently, the moving grains form a mobile layer (bed-load) that becomes unstable in some cases producing ripples and/or dunes, which interact with the flow. In industry, this is mainly associated with problems of pressure loss in closed conduits. This work presents an experimental study on the formation and migration of ripples in a turbulent flow. In the experiments, fully-developed turbulent water flows were imposed over a granular bed of known granulometry in a transparent closed-conduit. For different grain sizes and flow rates, a high-definition camera filmed the growth and migration of bedforms. The wavelength and the celerity of bedforms were determined from the acquired images through a numerical code developed in Matlab. The obtained results are compared with other published works in the area Mestrado Termica e Fluidos Mestre em Engenharia Mecânica

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Jadrnak, Sharon Marie. "Experimental studies of bimodal granular material flows." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/16107.

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Reis, Gabriela dos 1985. "Eficiência de filtros de areia recoberta com nanopartículas de prata na remoção de microesferas de poliestireno." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/257943.

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Orientador: Ricardo de Lima Isaac Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil, Arquitetura e Urbanismo Made available in DSpace on 2018-08-26T15:48:00Z (GMT). No. of bitstreams: 1 Reis_Gabrielados_M.pdf: 4501335 bytes, checksum: f41add1d19b9cc7987740fb6604a17ed (MD5) Previous issue date: 2014 Resumo: Dentre as etapas do tratamento de água para abastecimento público a filtração é essencial para remoção de partículas e microorganismos nocivos à saúde humana. Devido ao reduzido tamanho e resistência à cloração, os oocistos de Cryptosporidium tornam-se um problema nas estações de tratamento de água. Neste estudo foi investigada a eficiência da filtração em meio granular constituído de areia recoberta com nanopartículas de prata na remoção de microesferas de poliestireno, que simulam oocistos de Cryptosporidium spp.. A presença das nanopartículas de prata pode ser uma barreira adicional no tratamento de água, proporcionando ao grão de areia uma camada positiva, auxiliando na remoção de oocistos. O sistema de filtração em escala de laboratório foi composto de microcolunas de vidro borossilicato (diâmetro interno 1 cm) preenchidas com areia previamente impregnadas por imersão em solução de nanopartículas de prata (concentração 0,1 g/L). Os filtros foram alimentados por uma suspensão de água deionizada contendo microesferas de poliestireno (diâmetro médio 2 ?m). A influência na qualidade da água na filtração foi avaliada quanto aos parâmetros: concentração de ácido húmico (2,5, 5,0 e 10,0 mg.L-1), pH (6, 7 e 8), força iônica (24, 48 e 105 mM) e concentração inicial de microesferas (1,3 x 105, 2,4 x 106 e 1,4 x 107 partículas/mL). O efeito do parâmetro taxa de filtração foi avaliado sob a condição operacional de 2,4, 4,8 e 48 m3/m2.dia. A remoção de partículas do filtro proposto foi da ordem de 99,0 % contra 92,0 % do filtro controle. Os filtros teste constituídos de camada de areia recoberta com prata tiveram desempenho superior, na remoção da turbidez, aos filtros controle, com eficiência de remoção da ordem de 81,1 %, ao se filtrar até 10 VP (volume de poros). Contudo, a turbidez não se mostrou um bom indicativo da remoção de microesferas. A impregnação por nanopartículas de prata tornou os filtros mais eficientes na remoção de microesferas de poliestireno que simulam oocistos de Cryptosporidium Abstract: Among the steps in treating water for public supply filtration is essential for removal of particles and microorganisms harmful to human health. Due to the small size and resistance to chlorination, Cryptosporidium oocysts become a problem in water treatment stations. This study investigated the efficiency of the filtration medium consisting of granular sand coated with silver nanoparticles in the removal of polystyrene microspheres that simulate Cryptosporidium spp.. Presence of silver nanoparticles can be an additional barrier for water treatment, providing a positive layer, aiding in the removal of oocysts. The filtration laboratory scale system was composed of borosilicate glass micro columns (inner diameter 1 cm) filled with sand previously impregnated by immersion in a solution of silver nanoparticles (concentration 0.1 g/L). The filters were fed with a suspension of deionized water containing polystyrene microspheres (mean diameter 2 ?m). The influence on water quality in filtration was evaluated for the following parameters: concentration of humic acid (2.5, 5.0 and 10.0 mg.L-1), pH (6, 7 and 8), ionic strength (24, 48 and 105 mM) and initial concentration of microspheres 1.3 x 105, 2.4 x 106 and 1.4 x 107 particles/ml). The effect of the filtration rate parameter was evaluated under operating conditions of 2.4, 4.8 and 48 m3/m2.day. The removal of particles of test filter was approximately 99.0 % compared with 92.0 % of the control filter. The test filters consisting of silver coated sand layer exhibited superior performance in the removal of turbidity, the control filters, with removal efficiency of about 81.1 % when filtering up to 10 filter PV (pore volume). However, turbidity was not a good indicator of removal of microspheres. The impregnation with silver nanoparticles made filters more effective on the removal of polystyrene microspheres that simulate Cryptosporidium oocysts Mestrado Saneamento e Ambiente Mestra em Engenharia Civil

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Dissertations / Theses on the topic 'Granular materials'

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