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1
Smith, James Seymour. "Scaled geotechnical centrifuge modelling of gelifluction." Thesis, Cardiff University, 2004. http://orca.cf.ac.uk/54676/.
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This thesis describes the laboratory modelling of gelifluction processes using the geotechnical centrifuge technique. Thirteen 1/10 scale planar slope models were frozen from the surface downwards on the laboratory floor and thawed, also from the surface downwards, under gravitational acceleration of 10 gravities (approximately 98.1 ms'2). A natural sandy silt soil from Quaternary periglacial slope deposits collected in SW England formed the base test material and slope models at gradients 4, 8, 12 and 16 were constructed using this soil. 10% and 20% by weight increments of glaciolacustrine silt and Kaolinite clay were added to the natural soil and a series of slope models were constructed at gradients of 4, 8, and 12 using these soils. Each slope model was subjected to four cycles of freezing and thawing except for the four slope models that underwent rapid slope failure. During thaw, soil temperatures and pore water pressures were recorded continuously, together with soil thaw settlement and surface displacement. Following each experiment, models were sectioned to observe displacement columns that showed the profiles of soil movement and allowed volumetric displacements to be calculated. It was shown that thaw settlement and slope gradient strongly affected the rate of surface movement and the subsurface profile of movement. Increasing slope gradient generated greater amounts of subsurface and surface movement as a function of increased gravitational shear stress. Thawing ice lenses inclined parallel to the slope gradient provided localised zones of microshearing in response to localised low frictional resistance. Rates of movement increased between the 4 and 8 models, but a greater increase occurred between the 8 and 12 models. A slope failure was initiated within the 16 slope model. Rates of gelifluction were dominantly influenced by increasing silt content impacting upon the distribution of segregated ice and the reduction of frictional shear strength. Increasing silt content generated high positive porewater pressures commonly in excess of hydrostatic and consequently greater amounts of pre-failure strain. A clear behavioural threshold was identified between the 10% and 20% silt soils, with far greater gelifluction in the latter than the former. Increasing clay content had a less pronounced impact upon rates of gelifluction when compared to increasing silt due to cohesion. Rates of movement increased between the 10% and 20% clay in response to lower shear strength. A sawtooth style of pore pressure response caused by water escape events within the 20% clay prevented maximum potential pressures being achieved and possibly impacted upon the overall rate of gelifluction. A successful simulation of both landsliding and slow mass wasting processes was undertaken and future applications for the technique have been outlined.
2
Lemoine, Elise Marie Jeanette Simone. "Modelling sand production in a geotechnical centrifuge." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ48275.pdf.
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Louw, Hendrik. "Modelling horizontally loaded piles in the geotechnical centrifuge." Diss., University of Pretoria, 2020. http://hdl.handle.net/2263/73182.
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Pile foundations are extensively used to support various structures that are constructed in soft/loose soils, where shallow foundations would be considered ineffective due to low bearing capacities and large settlements. The design of these structures to accommodate lateral applied loads in particular, usually imposed by winds, water and earth pressures, has gained popularity over the past few decades. The behaviour of horizontally loaded piled foundations is a complex soil-structure interaction problem and is usually concerned with the relative stiffness between the pile and the surrounding soil, where the relative stiffness is a function of both the stiffness and properties of the pile and the stiffness of the soil.
Many design assumptions and methods used for pile foundations are based on the principles observed from metal piles. This raises the question of the validity and accuracy of assumptions and methods for the use of analysing and designing reinforced concrete piles, that exhibits highly non-linear material behaviour and changing pile properties after cracking. Due to the elastic behaviour of metal sections, these methods typically only focus on the soil component of the soil-structure interaction problem, only allowing changes and non-linear behaviour of the soil surrounding the pile to take place upon load application, mostly disregarding the behaviour and response of the pile itself.
The main purpose and objective of the study was to determine whether aluminium sections in a centrifuge could be used to realistically and sufficiently accurately model the monotonic and cyclic response of reinforced concrete piles subjected to lateral loading. This was observed though a number of tests conducted in a geotechnical centrifuge on scaled aluminium and reinforced concrete piles, subjected to both monotonic and cyclic loading.
After conducting the tests on both the scaled aluminium and reinforced concrete piles in the centrifuge it was concluded that aluminium sections cannot be used to accurately model and predict the lateral behaviour of reinforced concrete piles. Both the scaled aluminium and reinforced concrete piles proved to model the concept of laterally loaded piles quite well regarding bending at low loads. However, even at low lateral loads, the observed response of the scaled reinforced concrete was significantly different than that observed from the scaled aluminium pile. Furthermore, as the magnitude of the applied load and bending increased, the scaled reinforced concrete pile cracked, resulting in non-linear behaviour of the section under loading, which was not the case for the scaled aluminium pile that remained uncracked. This contributed to the difference in behaviour between the piles studied, therefore, the true material behaviour and failure mechanisms involved with reinforced concrete piles were not replicated by using a scaled aluminium pile section. The non-linear behaviour of the scaled reinforced concrete pile after cracking affected both the behaviour of the pile, as well as the response of the soil surrounding the pile, in contrast with the behaviour observed from the scaled aluminium pile.Dissertation (MEng)--University of Pretoria, 2020.
The Concrete Institute
Concrete Society of Southern Africa
WindAfrica project
Civil Engineering
MEng (Structural Engineering)
Unrestricted
4
Begaj, Qerimi Leonora. "Geotechnical centrifuge model testing for pile foundation re-use." Thesis, City, University of London, 2009. http://openaccess.city.ac.uk/17452/.
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In recent years development is at premium in many European cities. With life cycles of 25-30 years of buildings in financial cities and about 40 years in regional centres the ground is becoming more and more congested with redundant foundations. As the underground development of services and infrastructure already confines the location of building foundations, redundant foundations only add to this problem. The research described in this thesis, using centrifuge model testing, describes how the existing pile foundations in overconsolidated clay are likely to behave when their loading conditions are changed by unloading caused by demolition and subsequent reloading. This is done with the view to re-use the existing pile foundations for the new redevelopments. The influence of the new foundations on the existing foundations is also described. By re-using the foundations, the use of raw materials is reduced, the energy consummation for construction is reduced, the volume of soil from foundation construction is eliminated and the construction time significantly reduced, consequently reducing the whole costing of a structure. Experimental data was obtained from series of twenty one centrifuge model tests undertaken at 60g. The geometry of the model was such that it was possible to test two sets of foundations with each test. The performance of piles in overconsolidated clay when subjected to load/unload/reload cycles and the influence of supplementary piles used to achieve the required capacity were investigated. The model tests include comparison of the behaviour of bored piles when supplemented with mini piles of different length, number and spacing (centre to centre distance between the mini piles and the existing centre pile). An increase in capacity was observed when single piles were subjected to load cycles. It was found that this increase in capacity is dependent on the previous loading conditions of the pile. The behaviour of enhanced piles was characterised using a single pile test as datum test. The influence of these novel pile groups on the existing pile was dependent on the number, length of the mini-piles in the group and centre to centre spacing between the existing and new pile foundation.
5
Taunton, Paul R. "Centrifuge modelling of soil/masonry structure interaction." Thesis, Cardiff University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244112.
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Mokrani, A. "Centrifuge and finite element modelling of buried flexible culverts." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233377.
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Depountis, Nikos. "Geotechnical centrifuge modelling of capillary phenomena and contaminant migration in unsaturated soils." Thesis, Cardiff University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364759.
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Brouwers, Luke Bernhard. "Geotechnical Centrifuge Modelling of Variably Saturated Flow at The Soil-Rock Interface." Diss., University of Pretoria, 2017. http://hdl.handle.net/2263/63229.
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The underlying mechanisms governing unsaturated flow from soil into fractured rock in
the intermediate fractured vadose zone is still poorly understood despite occurring in
numerous areas of application. To gain a better understanding of these mechanisms, a
series of physical experiments using a geotechnical centrifuge are performed. The
centrifuge model comprises of two Perspex® sheets bent to form a clean smooth parallel
1mm aperture single discrete fracture that is inclined 90º, 75º and 60º from horizontal,
where dry sand is placed on top and water is supplied as continuous and intermittent
influx styles. The presence of the interface shows the development of perched water
system and saturated wetting front along the interface, which supports the capillarydominant
conceptual models for the fractured vadose zone. Breaching through the
interface occurred from preferential feeding pathways in the soil as multiple point
sources in the fracture and flow regimes composing of droplets, tendrils with droplet
formation and numerous types of rivulets indicating that fluxes within the fracture
range between 1 x 10-8 < Q < 1 x 10-4 m3/s per m. Changing the influx styles did not
alter the flow mechanisms occurring within the fracture. However, intermittent influx
did provide larger saturated wetting fronts along the interface while continuous influx
promotes flow instability within the fracture. Altering the fracture inclination influenced
the dominant flow mechanisms within the fracture but full saturation is never achieved
but rather only a potential 5 - 30% cross-sectional area contributes to flow, which
further decreases with depth due to merging of rivulets in upper regions of the fracture.
Although the results from the geotechnical centrifuge model may not be scaled to
prototype conditions due to similitude not being achieved between the Capillary and
Bond numbers, observations of breaching of the soil-rock interface, flow mechanisms
and flow instabilities within the fracture are similar in both the 1g and 20g experiments
indicating gravity driven flow instability maintains similitude and the geotechnical
centrifuge model offers a representative indication of natural conditions. The
contrasting support for both conceptual models regardless of fracture inclination
indicates that variably saturated flow at the soil-rock interface is a combination of the
two current conceptual models, with capillary flow dominating in soil material and the
dominant flow regime present within the fracture dependant on the interaction of
interfacial capillarity, gravitational and viscous forces. Ultimately the improved
conceptualisation and understanding gained from these experiments will benefit
hydrogeological as well as geotechnical areas of application such as hillslope hydrology,
contaminant transport, groundwater recharge, slope stability, differential settlement,
waste disposal, rock mass stress distributions, grouting and seepage into excavations.Dissertation (MSc)--University of Pretoria, 2017.
Water Research Commission
Geology
MSc
Unrestricted
9
Hurley, Shawn J. "Development of a settling column and associated primary consolidation monitoring systems for use in the geotechnical centrifuge : investigation of geotechnical-geophysical correlations /." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0009/MQ42397.pdf.
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10
Iglesia, Geraldo R. (Geraldo Ramiro). "Trapdoor experiments on the centrifuge--a study of arching in geomaterials and similitude in geotechnical models." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/113811.
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11
Jones, Brendon Ronald. "Geotechnical centrifuge modelling of the behaviour of a compressible clay horizon underlying a reinforced sand foundation." Diss., University of Pretoria, 2014. http://hdl.handle.net/2263/40363.
Full textAbstract:
Basal reinforcement, where high tensile geogrids are employed beneath structures, is becoming an
increasingly accepted construction technique along the eastern coast of southern Africa. The presence
of compressible, soft, thin and shallow clay horizons usually associated with complex estuarine or
lagoonal deposits are a major consideration when using basal reinforcement as a founding technique.
Basal reinforcement involves the use of high tensile strength geogrids beneath a structure to form a
reinforced sand foundation. Deformation behaviour under loading is an important component of
stability analysis of earth structures. If reinforcement is used, the mechanisms become altered.
Geotechnical centrifuge modelling is a unique physical modelling technique, as it allows replication
of in situ stresses, which is most important because soil behaviour is a function of stress. This is
achieved by placing the model at the end of the centrifuge arm, and subjecting it to an increased
gravitational field, which creates the correct stress distribution in the model. Centrifuge modelling
provides an appropriate technique to observe the behaviour of compressible, soft, thin and shallow
clay horizons when basal reinforcement is utilized. An appropriate centrifuge model was constructed
and compared the behaviour of the clay horizon under unreinforced and reinforced conditions.
Reinforcement configurations were adjusted to observe the influence of additional geogrid layers, and
extension of the width of the reinforcement. It was found that deformation behaviour is distinctly
different between unreinforced and reinforced tests. Vertical deformation in the unreinforced test
localised to the region directly beneath the platform, with little lateral disturbance to the clay horizon
beyond the platform edge. As such, the sand directly beneath the platform acts as a deeper rigid
platform. The deformation behaviour of the clay horizon changes with the inclusion of reinforcement.
When reinforcement is included a wider portion of clay is deformed. The lateral width of this
deformation zone is controlled by the width of the reinforcement, as the applied load is spread. A
‘wide-slab’ effect is evident with an increase in the geogrid width, as the tensioned membrane-effect
is mobilised to increase the capacity of the reinforced foundation sand. This results in a wider portion
of the clay deforming. Addition of geogrid reinforcement to the sand foundation under a wide
platform load enhances deformation of the clay, but has the advantage of an increased load-bearing
capacity of the system. Furthermore, the addition of multiple layers of reinforcement contributes to
this increase in load-bearing capacity. Additionally, increasing the installation width of the
reinforcement contributes to an increased vertical load-bearing capacity. However, this resultant
increase is only mobilised after a certain amount of vertical displacement. This is likely due to the
reinforcement requiring a certain amount of vertical displacement to mobilise tension in order to
support the applied load. The behaviour of a thin compressible clay horizon changes with the
inclusion of reinforcement under a wide platform load. The deformation behaviour of the clay is
increased by additional layers of reinforcement as well as an increase in the width of the
reinforcement. However, the increase in deformation comes at the benefit of an increased vertical
load-bearing capacity of the reinforced foundation sand.Dissertation (MSc)--University of Pretoria, 2014.
gm2014
Geology
unrestricted
12
Ratnam, Sangkaran. "Geotechnical centrifuge modeling of the behavior of light nonaqueous phase liquids (LNAPLs) in sand samples under hydraulic flushing." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10849.
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Madden, Patrick. "The influence of structural details, geotechnical factors and environs on the seismic response of framed structures." Thesis, University of Dundee, 2014. https://discovery.dundee.ac.uk/en/studentTheses/c24ae223-999c-407c-bd3f-b461708dcbb3.
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Seismic events around the globe directly affect all ranges of structures, from complex and expensive ‘skyscrapers’ to simple frame structures, the latter making up a higher proportion of the number of structures affected as they are a much more common type of structure. The impact of a seismic event can be devastating, especially if adequate predictions of their impact and imposed structural response are not made during the design stage of the structure. Knowing what response to expect allows the engineer to design the structure to survive an event and protect the occupants. The structural response to a seismic event is very complex and can be affected by a wide range of structural, geotechnical and environ parameters. While larger, expensive structures make use of expensive, time consuming, finite element analytical procedures to determine their response the cheaper, simpler, frame structures have to make do with existing, simplified, spectral method predictions. This research firstly involves finite element analysis of simple frame structures, considering different structural and geotechnical parameters which may influence the seismic response, namely the stiffness of the structural joints, the geometry of the structure (influencing the individual structural element flexibility) and the foundation conditions (fixed base or shallow foundations with soil structure interaction). A range of frames, of varying geometry, are considered which mobilise different amounts of inter-storey drift, local rotation and global rotation response. The influence of soil structure interaction (SSI) and frame rigidity (i.e. the properties of the joints) on the response behaviour is investigated. The finite element database is then used to validate improved methods for predicting the spectral response parameters, specifically the natural period and damping of equivalent single degree of freedom (SDOF) systems, which include the effects of frame rigidity, geometry and SSI. Dynamic centrifuge testing is also carried out in order to further validate the improved spectral model for the case of real soil with shear dependant stiffness. The physical model testing is also extended to consider how environs, such as other structures in close proximity, influence the response of a structure.
14
Li, Xinyao. "CENTRIFUGE MODELLING AND NUMERICAL SIMULATION OF NOVEL HYBRID FOUNDATIONS FOR OFFSHORE WIND TURBINES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1594728306295576.
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Sobrinho, Rubens Ramires. "Método para proteção dos dados contra falhas de comunicação em redes de sensores sem fios." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-17012008-110514/.
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Este trabalho apresenta o desenvolvimento de um método para garantir a proteção dos dados contra falhas de comunicação, em redes de sensores inteligentes sem fios. A rede sem fios foi empregada nos ensaios de modelos físicos reduzidos em centrífuga para estudar o comportamento das âncoras \"tartaruga\", utilizadas nas linhas de ancoragem de sistemas oceânicos para produção de óleo e gás em águas profundas. O emprego da tecnologia de redes de sensores sem fios tem aumentado em muitas áreas da sociedade, principalmente na engenharia. Dessa forma, muitos problemas estão sendo enfrentados e estudados pelos pesquisadores. Sobretudo no que diz respeito à interferência ambiental, relação de potência e alcance, integridade da informação, miniaturização dos dispositivos, autonomia de energia, limitação de algoritmos e vida útil. A inserção da tecnologia de redes de sensores inteligentes sem fios nos ensaios de modelos físicos reduzidos em centrífuga, além de ser inédita no Brasil, permitirá avanços significativos na determinação de parâmetros que, atualmente, são de difícil obtenção com tecnologias convencionais como os sistemas de aquisição de dados e controle que utilizam cabos e fios. Muitas vezes depara-se com a inconveniência do peso dos cabos e dificuldades de instalação dos dispositivos nos modelos, pela sua pouca portabilidade.This work present a method development to guarantee of the integrity data in the wireless smart sensor networks, employed in centrifuge physical modeling tests of anchors used as fixing devices of deep water production oil and gas systems. The use of wireless smart sensor networks technology has been increasing in many engineering areas. In spite of this evidence, lots of problems are being faced and studied by the researchers, environmental interference, power and reach relations, integrity of the information, miniaturization of the devices, energy autonomy, algorithms and useful life. The use of the wireless smart sensor networks technology in the reduced physical models test in centrifuge, by first time in Brazil, will allow significant advances in the parameters determination. The conventional instrumentation presents inconvenience of the weight cables and difficulties of the devices in the models by limited portability.
16
Wu, Kuen-Wei, and 吳崑瑋. "Development of an FBG-Based Miniature Pore Pressure Transducer for Geotechnical Centrifuge Testing." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/925p52.
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碩士國立交通大學
土木工程系所
105
Electrical miniature pore pressure transducers (PPTs) have been widely used in geotechnical centrifuge modelling tests to measure the pore pressure variations in the test specimen. Among the available sensors, Druck PDCR81 series produced by GE Sensing and Inspection Technologies has been the most popular one. However, this electrical sensor can be affected by electromagnetic interference (EMI). Since the sensor diaphragm is made of silicon, the calibration factors can vary after a centrifuge test. In addition, the Druck PDCR81 PPTs may not work repeatedly with a linear response under negative pressure. These problems may lead to unreliable test results. To overcome these drawbacks, a miniature PPT was developed using optical fiber Bragg grating (FBG) as the sensing element in this research project. The design takes advantage of the unique capabilities of FBG that it is immune to EMI and moisture. A geotechnical centrifuge modelling test was performed at the University of Cambridge for verification of the FBG based PPT. The thesis describes the background of the research, design principles of the new FBG PPT and its performance based on available test results.
17
Jacobs, EMILY. "Centrifuge Modelling of Instability in Granular Soils under Infinite Slope Conditions." Thesis, 2013. http://hdl.handle.net/1974/8502.
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Rainfall induced granular flow slides pose a significant risk in many areas of the world. These failures, characterized by the sudden release of material in a fluid-like manner, are the result of static liquefaction occurring in these slopes. The static liquefaction phenomenon has been linked to instability.
Instability behaviour is primarily studied under undrained triaxial conditions, and although many instability theories have therefore been defined in this stress space, these have been shown to also extend into plane strain conditions. In order to further investigate this behaviour under these stress conditions, Wolinsky et al. (2013) developed a tilt-table soil box for use in a geotechnical centrifuge to analyze instability in infinite slope soil models. This testing apparatus has been used to simulate instability in plane strain under both dry and saturated soil conditions.
Stress-controlled experiments were performed on dry infinite slope soil models to investigate the effects of both void ratio and effective stress on instability behaviour. By performing these tests dry, this test apparatus provides the ability to decouple the triggers of instability from the corresponding response in pore pressure and the consequences. The results of this testing confirmed that the instability line angle is a function of both void ratio and effective stress. As the void ratio decreases and effective stress in the soil model increases, the resulting instability line angle will increase. This testing also demonstrated typical stress-dilatancy behaviour in these infinite slope models, characterized by contractive response in loose soils and dilative response in dense soil subject to increasing shear stress.
Secondly, this testing apparatus was used to investigate the effects of seepage force on instability behaviour in granular slopes through the introduction of groundwater seepage in the form of a rising groundwater level. Although the results illustrated shear and volumetric response to these increased pore water pressures, these were not significant enough to initiate instability and the resulting pore water response leading to failure. It has been determined that this apparatus must be further adapted to dissipate the matric suctions developed above the water table during groundwater rise.Thesis (Master, Civil Engineering) -- Queen's University, 2013-12-03 21:06:56.806
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Bryant, SARAH. "Physical Modelling of the Mobility of Dry Granular Landslides." Thesis, 2013. http://hdl.handle.net/1974/8311.
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In geotechnical engineering, granular flows are often studied as a means to further the understanding of the mechanisms that drive landslide motion. High quality experimental data is essential in providing evidence for the development and verification of new theoretical methods that link complex grain interactions to the extended mobility of some landslide events. At present, limited experimental data is available that captures the full range of landslide mobility. In an attempt to add to the present data sources, high quality experimental data was obtained through the use of high speed cameras and physical modelling using a geotechnical centrifuge and a large scale landslide flume. These modelling techniques allow for landslide motion, representative of field scale events, to be observed in a well-defined and controlled setting. A series of nine tests were performed in a geotechnical centrifuge under varying slope inclinations and Coriolis conditions. The effects of Coriolis on landslide mobility were evident when comparing final deposit shapes and total runout. The effects of Coriolis were more pronounced for higher velocity situations and when material was travelling on the horizontal base section opposed to the sloped section of the physical model. A series of thirty tests were performed using a large scale flume under varying source volumes and basal friction conditions, capturing the grain scale interactions and overall runout behaviour. The grain interactions and ultimately the flow behavioural regimes developed were a function of material source volume and boundary roughness. The dimensionless inertial number was used to classify flows into behavioural regimes, but was found to break down when describing transitions to the granular gas behavioural regime. The runout-time results and final deposit shapes showed significant variation between test configurations, indicating the effects of volume and basal friction on overall mobility. Using the depth averaged numerical model, DAN, it was found that a single set of empirically derived frictional parameters (i.e. specific to internal and basal friction conditions) was appropriate for matching the overall mobility of the experimental flows over a range of flow volumes and slope inclinations.Thesis (Master, Civil Engineering) -- Queen's University, 2013-09-25 15:48:54.761
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Wolinsky, Eric. "Investigation of Softening Instability Phenomena Under Simulated Infinite Slope Conditions in Centrifuge Tilting Table Tests." Thesis, 2014. http://hdl.handle.net/1974/12159.
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Element test results reported in the literature under both triaxial and plane strain conditions indicate that loose saturated granular specimens can experience softening instability at stress ratios lower than what might otherwise be expected given the critical state friction angle of the soil. The region of potential softening instability in stress-space is often explained using the framework of the instability line. This phenomenon is particularly relevant to shallow slopes of 1 to 2 m depth. However, the practical realities of sample preparation for triaxial testing make performing tests below 20 to 30 kPa of confining stress exceptionally difficult.
In this thesis, the development of a centrifuge tilt-table test device is described which aims to test the behaviour of loose granular slopes under stress paths of increasing slope inclination or increasing pore water pressure. A system of instrumentation including pore pressure transducers, inclinometers, displacement transducers, and high-resolution cameras was designed to monitor the behaviour of the slope model. The development of a system to provide a controlled groundwater level within the slope model proved to be particularly challenging. The results of two competing design concepts are presented for the water boundary condition and discussed.
The centrifuge tilt-table is used to compare the physical response of a slope to the behaviour predicted by the infinite slope and softening instability models using scale model centrifuge testing. If softening instability is a rigorous concept, it should be the primary observed failure mechanism as it will occur at a stress state below the failure line. Tests were performed on loose Ottawa F110 sand at 1g, 20g and 40g and 60g. Deviatoric strain-softening was observed in loose dry sand. The softening instability event resulted in a rapid increase in shear strain at constant shear stress while the soil was at a stress state below the failure envelope. Any soil that can experience softening instability (i.e. granular, loose, saturated, and behaves undrained) will undergo two failures: one caused by deviatoric strain-softening (softening instability) and a second caused by shear failure at a larger slope angle.Thesis (Master, Civil Engineering) -- Queen's University, 2014-04-29 22:01:36.786