Dissertations / Theses on the topic 'Slope modelling'
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1
Benko, Boris. "Numerical modelling of complex slope deformations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24004.pdf.
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Stevens, I. G. "Modelling pollutant dispersion and slope currents." Thesis, University of East Anglia, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372560.
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Tsaparas, Ilias. "Field measurement and numerical modelling of infiltration and matric suctions within slopes." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/1715/.
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Armstrong, Robert Claude 1961. "Slope stability modelling at the Cyprus Bagdad Mine." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/281472.
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The Bagdad Mine, an open pit mine located in northwestern Arizona, has experienced a slope failure related to a weak weathered tuff bed. The unit has been altered to a clay-like material in areas of the pit. Overburden pressures have caused the tuff to be squeezed out, and blocks of the overlying basalt unit have toppled forward. The failure has been remedied by reducing the pit slope to about 20°, but this solution is not desirable. Modelling of the slope is done using a general purpose finite element method program. The Drucker-Prager theory is used to model the tuff bed, while the other units are treated as being linearly elastic. Material properties for the three rock units are obtained from a variety of sources. Results suggest that loss of shear strength in the tuff, due to blasting-induced liquefaction, may be the cause of slope failure. Suggestions are made for remedial action.
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Larsson, Martin. "Road Slope Estimation." Thesis, Linköping University, Automatic Control, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-53884.
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Knowledge about the current road slope can improve several applications in a heavy-duty vehicle such as predictive cruise control and automated gearbox control. In this thesis the possibility of estimating the road slope based on signals from a vehicles air suspension system has been studied. More specifically, the measurement consists of a pressure signal measuring the axle load, and a vertical distance sensor.
A variety of suspension systems can be mounted on a Scania truck. During this thesis, two discrete-time models based on two different rear axle air suspension systems have been proposed. The models use the effect of alternating axle load during a change in the road slope and the estimates are computed using an extended Kalman filter.
The first model is based on a rear axle suspension known as the 2-bellow system. This type of suspension is strongly affected by the driveshaft torque, which results in a behaviour where the rear end is pushed upwards and thus decreasing the rear axle load during uphill driving. A model was developed in order to compensate for this behaviour. Unfortunately, the estimates showed less promising results and all attempts to determine the error was unsuccessful.
The latter model is based on the 4-bellow system. This suspension system is not affected by the driveshaft torque and a less complex model could be derived. The experimental results indicated that road slope estimation was possible and with a fairly accurate result. However, more work is needed since the estimate is affected by road surface irregularities and since the algorithm requires knowledge about the vehicles mass and the location of the centre of gravity.
All the presented results have been estimated based on real data from a test track at Scania Technical Centre in Södertälje.
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Arnold, Patrick. "Probabilistic modelling of unsaturated slope stability accounting for heterogeneity." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/probabilistic-modelling-of-unsaturated-slope-stability-accounting-for-heterogeneity(fb3d214c-8a42-4a2c-81c2-bda45e9ae7af).html.
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The performance and safety assessment of geo-structures is strongly affected by uncertainty; that is, both due a subjective lack of knowledge as well as objectively present and irreducible unknowns. Due to uncertainty in the non-linear variation of the matric suction induced effective stress as a function of the transient soil-atmosphere boundary conditions, the unsaturated state of the subsoil is generally not accounted for in a deterministic slope stability assessment. Probability theory, accounting for uncertainties quantitatively rather than using "cautious estimates" on loads and resistances, may aid to partly bridge the gap between unsaturated soil mechanics and engineering practice. This research investigates the effect of uncertainty in soil property values on the stability of unsaturated soil slopes. Two 2D Finite Element (FE) programs have been developed and implemented into a parallelised Reliability-Based Design (RBD) framework, which allows for the assessment of the failure probability, failure consequence and parameter sensitivity, rather than a deterministic factor of safety. Utilising the Random Finite Element Method (RFEM), within a Monte Carlo framework, multivariate cross-correlated random property fields have been mapped onto the FE mesh to assess the effect of isotropic and anisotropic moderate heterogeneity on the transient slope response, and thus performance. The framework has been applied to a generic slope subjected to different rainfall scenarios. The performance was found to be sensitive to the uncertainty in the effective shear strength parameters, as well as the parameters governing the unsaturated soil behaviour. The failure probability was found to increase most during prolonged rainfall events with a low precipitation rate. Nevertheless, accounting for the unsaturated state resulted in a higher slope reliability than when not considering suction effects. In a heterogeneous deposit failure is attracted to local zones of low shear strength, which, for an unsaturated soil, are a function of both the spatial variability of soil property values, as well as of the soil-water dynamics, leading to a significant increase in the failure probability near the end of the main rainfall event.
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Jones, Alun M. C. "Centrifuge modelling of soil nailing : an investigation of lifetime performance." Thesis, Cardiff University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248162.
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Franz, Juergen Mining Engineering Faculty of Engineering UNSW. "An investigation of combined failure mechanisms in large scale open pit slopes." Publisher:University of New South Wales. Mining Engineering, 2009. http://handle.unsw.edu.au/1959.4/43368.
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Failure mechanisms in large scale open pit slopes are more complex than could be considered through conventional slope design methods. Pit slope behaviour must be predicted accurately, because for very deep open pits, a small change of slope angle can have serious technical and economic consequences. Failure of hard rock slopes often involves both failure along naturally existing weakness planes and failure of intact rock. Without an advanced understanding of combined rock slope failure mechanisms, the validity of commonly applied methods of large scale slope analysis is questionable. The problem was investigated by means of a toolbox approach, in which a wide range of slope stability analysis methods were used and compared to address specific problems arising during slope design optimisation of the Cadia Hill Open Pit, NSW. In particular, numerical modelling is an advanced tool to obtain insight into potential failure mechanisms and to assist the slope design process. The distinct element method was employed to simulate complex rock slope failure, including fracture extension, progressive step-path failure and brittle failure propagation, which were previously often considered unimportant or too difficult to model. A new, failure-scale-dependent concept for the categorisation of slope failures with six categories ranging from 0 (stable) to 5 (overall slope failure) was suggested to assist risk-based slope design. Parametric slope modelling was conducted to determine the interrelationship between proposed categories and critical slope/discontinuity parameters. Initiation and progression of complex slope failure were simulated and described, which resulted in an advanced understanding of combined slope failure mechanisms and the important role of rock bridges in large scale slope stability. A graphical presentation of the suggested slope failure categories demonstrated their interrelationship to varied slope/discontinuity parameters. Although large scale slope analyses will always involve data-limited systems, this investigation shows that comprehensive, conceptual modelling of slope failure mechanisms can deliver a significantly improved insight into slope behaviour, so that associated slope failure risks can be judged with more confidence. The consideration of combined slope failure mechanisms in the analysis of large scale open pit slopes is essential if slope behaviour is to be realistically modelled.
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Wu, K. O. "The modelling of anisotropic jointed rock slopes by physical and numerical methods." Thesis, University of the West of Scotland, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234764.
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In this study the stabili ty and stress distribution of anisotropic jointed rock slopes under external loading were examined. The influence of joint orientation and mechanical characteristics on the engineering behaviour of jointed rock slopes were included in the investigation. A total of four physical models were developed by using blocks of light-weight concrete and gypsum mortar to simulate intact rocks and joints respectively. The models were built within a confining frame such that plane strain conditions were maintained throughout the experiments. The stress-strain relationship and the strength of the model blocks were determined from laboratory tests. An empirical equation was established to represent the strength envelope of the model material and rocks in general. The normal and shear properties of the model rock JOints were examined, and were described by mathematical expressions in order to facilitate the numerical studies. Results from the physical modelling studies showed that localised failure regions were induced and three types of failure modes were identified. The stability and stress distribution wi thin the models were found to be significantly influenced by the properties and system of the jointing. Two computer programs were developed based on the Finite Element Method and Coupled Finite-Boundary Element Method in order to simulate the behaviour of jointed rock masses and assessments of their application were made in comparison with the physical modelling results. A special finite joint element was developed to incorporate the non-linearity and anisotropy behaviour of rock joints. The finite element program was successfully executed and gave reasonable results in which the principal stress distributions were generally in agreement with those obtained from the physical models. The finite-boundary element program on the other hand introduced boundary incompatibility in the system and therefore led to divergency.
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Rowland, James D. "Modelling solar irradiance on a slope under a leafless deciduous forest." Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=59293.
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This thesis investigates variations in solar irradiance incident upon sloping surfaces under deciduous forest in winter. A model is presented for prediction of solar irradiance at the surface which accounts for slope inclination and orientation, surrounding topography, isotropic absorption of solar radiation by the crown space, and shadows cast by the stem space.Field data from two sites of different slope and aspect attest to the validity of the model; errors, based on 20-minute averages of instantaneous values, are 15.5% (RMSE) and $-$1.9% (MBE). Error is partially due to reliance upon global radiation measurements above canopy at a different site (partially cloudy conditions) and sampling error (sunny sky conditions). The variability of solar irradiance at the surface, and in the error of predicted values, is found to vary with sky condition, solar zenith and incidence angles, and slope orientation. However, integration to hourly and/or daily time periods improves model performance significantly.
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Wooller, Luke K. "Synaptic and analogue modelling studies of volcano deformation and slope stability." Thesis, Open University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.407060.
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Styles, Thomas Daniel. "Numerical modelling and analysis of slope stability within fracture dominated rock masses." Thesis, University of Exeter, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496103.
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Numerical modelling of rock slopes can involve a number and variety of techniques, the selection and requirement of which depends on the factors deemed to control the potential for Instability. This thesis presents a number of case studies involving slopes in fractured rock, encompassing a range of scales. The case study slopes have provided a means to question the way in which particular slope instabilities should be analysed. Currently there are few methods available for analysing the complex behaviour within slopes of fractured rock. A review of available techniques is given within this thesis, with the use of limit equilibrium, finite element and hybrid methods, to highlight their specific advantages and limitations for the chosen case study slopes. By modelling slope Instability within fractured rock, the understanding of both discrete and mass behaviour increases considerably. Numerical modelling can therefore be used as a tool to help improve both the safety and efficiency of open pit mining and the management of natural rock slopes.
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Maguire, Andrew J. "Numerical modelling of the stable atmospheric boundary layer overlying a uniform slope." Thesis, University of Sheffield, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287633.
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Zhang, Xiaoyang. "Soil-erosion modelling at the global scale using remote sensing and GIS." Thesis, King's College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321948.
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Hartshorne, James Byng. "Assessing the influence of digital terrain model characteristics on tropical slope stability analysis." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336822.
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Alcantara-Ayala, Irasema. "Modelling mass movement risk under semi-arid mountainous conditions : the Alpujarride complex, Spain." Thesis, King's College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267249.
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Szuman, Magdalena Katarzyna. "Forward seismic modelling and spectral decomposition of deepwater slope deposits in outcrop and subsurface." Thesis, University of Aberdeen, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=105419.
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This project aimed to constrain the interpretation uncertainties associated with reflection seismic data of deep-water slope deposits. The basic premise of the project is that seismic data is affected by small-scale architectural elements and even conventional low-frequency data may contain clues of the sub-seismic geometries. These can be decoded by understanding the interaction between internal elements and the seismic wavelet. A series of outcrop-derived forward seismic models was created, representing different types of outcrop based slope deposits. The seismic interpretation of the forward models was based on amplitude analysis supplemented by instantaneous attributes and spectral decomposition. In order to create realistic synthetic seismograms, input models included geometries whose thickness was as low as 1% of the resolution limit. By revealing the influence of small-scale structures on synthetic seismic data at the high end of the spectrum (70Hz to 100Hz), the knowledge of tuning effects and the interaction between interfering reflections at lower frequencies (i.e. 20, 40 and 60Hz) could potentially be significantly improved. The gained experience was then applied to real seismic data. It was proven that small-scale geometries have an additional, highly significant effect on the composite reflection. Because of the inherent non-uniqueness in seismic reflection, the specific seismic forward models of particular outcrop analogues can only be used as guides to the seismic interpretation of the particular architectural elements of a subsurface deposit and not as definite models against which one can definitely pattern match real and modelled seismic data. as burial depth increases, so does the non-uniqueness of the seismic interpretation of seismic data from deposits whose internal geometries are around/below the tuning thickness.
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Nelis, Simon Brett. "Modelling rock slope behaviour and evolution with reference to Northern Spain and Southern Jordan." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/2206/.
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The geomorphological behaviour of steep jointed rock slopes has been studied using distinct element computer models. In order to model steep slopes effectively, methodologies need to be combined from the studies of environmental modellers, geomorphologists and engineers. The distinct element method is ideal for the study of the development of jointed rock masses, where the failure is controlled by the nature of the discontinuities. Theoretical modelling identified that block size is a key control affecting the deformation of rock masses. Deformation of rock masses with smaller block assemblages is greater than for rock masses composed of larger block sizes. This is due to the increased magnitude of joint normal closure. Catastrophic failure is less likely in slopes with smaller block sizes because the shear strength is greater in a closely jointed rock mass. These slopes are more likely to undergo gradual deformations. Block-size effects are also responsible for influencing the failure mechanism of rock masses. As block size decreases, the magnitude of block rotation increases and the failure mechanism changes from sliding to toppling. The effect of slope scale on the deformation properties of the rock masses has also been investigated. Two field locations, the Picos de Europa mountains, northern Spain and Wadi Rum, southern Jordan, have been chosen to provide a link between the theoretical modelling and classic rock landforms which are controlled by the discontinuity geometry. Given the sporadic and infrequent occurrence of failure events at the field sites, a computer modelling approach has been adopted to analyse slope behaviour. In the Picos de Europa, slope deformations are deep-seated, with sliding and toppling being the dominant modes of failure. Much of the slope deformation in these mountains is a result of post-glacial rock-slope deformation. The sandstone inselbergs of Jordan show a range of morphologies from rounded hills to vertical cliffs. The morphology of the inselbergs is related to the intact rock strength; stronger Red lshrin sandstone forms vertical slopes, whereas the weaker Disi sandstone forms rounded domes. Jointing in the area is sub-vertical with horizontal bedding and computer simulations have shown that toppling is the dominant mode of failure in these inselbergs. Comparison of computer model output suggests that different failure mechanisms have distinct failure signatures. Catastrophic, deep-seated failures are characterised by a long period of acceleration as the failure propagates through the rock mass and infinite velocity is reached. Non-catastrophic slope movements, such as self-stabilising topples, are characterised by short periods of acceleration followed by small creep movements at a constant velocity. Computer modelling has indicated that scale effects do exist in the modelled rock masses from the Picos de Europa and particularly Wadi Rum. In areas where jointing is constant, the relative block size of the rock mass decreases as slope scale increases. The greater numbers of blocks along with greater in situ stresses influence the failure of the slope. Cosmogenic dating was used to temporally constrain UDEC model output and provide a better understanding of rock slope failure mechanisms in the Picos de Europa and Wadi Rum. Dating indicated delayed paraglacial adjustment was the triggering mechanism for slope failure in the Picos de Europa, whereas failures in Wadi Rum appeared to be closely linked with wetter climatic conditions.
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CAMONES, LUIS ARNALDO MEJIA. "MODELLING OF STEP-PATH TYPE FAILURE MECHANISMS IN FRACTURED ROCK SLOPE USING DISCRETE ELEMENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=33108@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Diferentes mecanismos de ruptura são considerados no momento de avaliar a estabilidade de um maciço rochoso fraturado. Entre estes, os mecanismos de ruptura tipo planar, em cunha e tombamentos têm sido estudados intensivamente, existindo atualmente modelos matemáticos que permitem avaliá-los. Estes mecanismos de ruptura são restritos a taludes pequenos e com fraturas contínuas, nas quais o deslizamento ocorre ao longo destas descontinuidades. Em casos de taludes de grande altura ou quando a persistência das fraturas é pequena em relação à escala do talude, o fraturamento torna-se descontínuo. Neste caso, o mecanismo de ruptura mais provável é o tipo Step-Path, o qual, a superfície de ruptura é formada por fraturas que se propagam através da rocha intacta juntando-se entre elas. Este fenômeno de união de fraturas é chamado de coalescência. Análises de estabilidade, como os probabilísticos ou por equilíbrio limite, são usados atualmente para avaliar estes tipos de rupturas, não se tendo ainda o desenvolvimento de um modelo numérico que possa representá-lo e reforçar estas teorias. O presente trabalho avalia o uso do Método dos Elementos Discretos na modelagem do mecanismo de ruptura tipo step- path, realizando uma análise de estabilidade que permita comparar os seus resultados com o método de equilíbrio limite. Foi utilizado o programa PFC nas versões 2D e 3D, assim como o programa FracGen para a geração de fraturas tridimensionais. A análise tridimensional foi feita mediante um acoplamento PFC3D-FracGen. A pesquisa inclui a análise e modelagem dos fenômenos de coalescência em amostras, assim como a influência da anisotropia na resistência das rochas em ensaios triaxiais.
Different failure mechanisms are considered when a fracturated rock mass is valued. Some of them are being subject of accurate study, like planar failure mechanism, wedges and toppling, which are currently valued by mathematical models. These failure mechanisms are restricted to small slopes and with continue fractures, where the sliding occurs along these discontinuities. To height slopes or when the fracture persistence is smaller than the slope scale, the fracturing becomes discontinuous. In this case, the most probable failure mechanism to happen is the step-path type, in which the failure surface is composed by fractures that propagate through the intact rock and that are joined together. This phenomenon of fracture union is known as coalescence. Stability analysis, like probability analysis or limit equilibrium analysis are currently utilized to evaluate this kind of failures, but its important to develop a numerical model to represent and reinforce these theories. This work aims to evaluate the use of Discrete Element Method to model step-path failure mechanism on a stability analysis and to compare the results with limit equilibrium method. The program used to simulate the slope is PFC (2D and 3D) and the program FracGen was used to generate three-dimensional fractures. Three-dimensional analysis was done by a coupling between PFC3D and FracGen. The research includes the analysis and modeling of coalescence phenomenon on rock samples, as well as the analysis of the anisotropy influence on rock strength obtained from triaxial tests.
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Smith, Alister. "Quantification of slope deformation behaviour using acoustic emission monitoring." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/18593.
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Early warning of slope instability will enable evacuation of vulnerable people and timely repair and maintenance of critical infrastructure. However, currently available warning systems are too expensive for wide-scale use or have technical limitations. The acoustic emission (AE) monitoring approach using active waveguides (i.e. a steel tube with granular backfill surround installed in a borehole through a slope), in conjunction with the Slope ALARMS AE measurement system, has the potential to be an affordable early warning system for slope instability. However, the challenge has been to develop strategies to interpret and quantify deformation behaviour from measured AE. The development of an approach to quantify slope deformation behaviour from measured AE will enable the AE monitoring system to provide early warning of slope instability through detecting, quantifying and communicating accelerations in slope movement. Field monitoring and full-scale physical modelling have been conducted to characterise the AE response from the system to both reactivated slope movements and first-time slope failure. Definitive field evidence has been obtained showing AE monitoring can measure slope movements and generated AE rates are proportional to slope displacement rates, which was confirmed through comparisons with both conventional inclinometer and continuous ShapeAccelArray deformation measurements. A field monitoring case study demonstrated that the AE approach can detect very slow slope movements of 0.075 mm/day. In addition, the concept of retrofitting inclinometer casings with active waveguides to convert the manually read instrument to a real-time monitoring system has been demonstrated using a field trial. Dynamic strain-controlled shear tests on active waveguide physical models demonstrated that AE monitoring can be used to quantify slope displacement rates, continuously and in real-time, with accuracy to within an order of magnitude. Large-scale first-time slope failure experiments allowed the AE response to slope failure to be characterised. AE was detected after shear deformations of less than a millimetre in previously un-sheared material, and AE rates increased proportionally with displacement rates as failure occurred. The AE rate-displacement rate relationship can be approximated as linear up to 100 mm/hour and shear surface deformations less than 10-20 mm. At greater velocities and larger deformations the gradient of the relationship progressively increases and is best represented using a polynomial. This is because complex pressure distributions develop along the active waveguide analogous to a laterally loaded pile, and the confining pressures increase. Variables that influence the AE rate-displacement rate relationship have been quantified using physical model experiments and empirical relationships. A framework has been developed to allow AE rate-displacement rate calibration relationships to be determined for any AE system installation. This provides a universal method that can be used by practitioners when installing AE systems, to calibrate them to deliver alarm statuses/warning levels that are related to slope displacement rates. Use of this framework has been demonstrated using a case study example, and decision making protocols have been suggested that use trends in alarms with time to trigger decisions, which could be to send an engineer to inspect the slope, manage traffic, or evacuate people.
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Postill, Harry E. "Weather-driven clay cut slope behaviour in a changing climate." Thesis, Loughborough University, 2018. https://dspace.lboro.ac.uk/2134/35832.
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Long linear earthwork assets constructed in high-plasticity overconsolidated clay are known to be deteriorating due to long-term effects of wetting and drying stress cycles as a result of seasonal weather patterns. These stress cycles can lead to shallow first-time failures due to the mobilisation of post-peak strength and progressive failure. Design requirements of new earthworks and management of existing assets requires improved understanding of this critical mechanism; seasonal ratcheting. Incremental model development and validation to allow investigation of multiple inter-related strength deterioration mechanisms of cut slope behaviour in high-plasticity overconsolidated clay slopes has been presented. Initially, the mechanism of seasonal ratcheting has been considered independently and a numerical modelling approach considering unsaturated behaviour has been validated against physical modelling data. Using the validated model, the effects of slope geometry, design parameter selection and design life have been considered. Following this, an approach to allow undrained unloading of soil, stress relief, excess pore water pressure dissipation, seasonal ratcheting and progressive failure with wetting and drying boundary conditions has been considered. Hydrogeological property deterioration and the potential implications of climate change have been explored using the model. In both cases the serviceable life of cut slopes is shown to reduce significantly in the numerical analyses. Finally, a model capable of capturing hydrogeological behaviour of a real cut slope in London Clay has been developed and validated against long-term field monitored data. Using the validated model, a climate change impact assessment for the case study slope has been performed. The numerical analyses performed have indicated that seasonal ratcheting can explain shallow first-time failures in high-plasticity overconsolidated clay slopes and that the rate of deterioration of such assets will accelerate if current climate change projections are representative of future weather.
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Fischer, Luzia. "Slope instabilities on perennially frozen and glacierised rock walls : multi-scale observations, analyses and modelling /." Zürich : Geograph. Inst. der Univ. Zürich, 2009. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=018957681&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Qu, Feixiong. "Effects of modified river cross-section geometry on hydraulic modelling performance: the slope break method." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297668.
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Remote sensing data has been widely used for large scale hydraulic modelling in the world. One of the most common ways to collect remote sensing data is by satellite. The digital elevation data observed from space is publicly accessible and covers almost all areas of the earth. However, the satellite cannot observe the river bathymetry. The satellite-derived river cross-sections only contain the bank information above the surface water level. The level of accuracy of river cross- sections derived from remote sensing data is not enough and it is possible to have a large influence on the model performance. This study will explore the capability of the slope-break method to improve the river bathymetry estimation and the influence of improved river cross-sections on the hydraulic model performance. First, four synthetic river cross-sections are constructed with consideration of the feature of satellite-obtained data. Second, the study tests the parameter influence in the slope-break method to improve the river bed elevation estimation. Third, the performance of hydraulic models is evaluated through several simulations, which focus on the input data collected during the different satellite observation period, the influence of modified submerged river cross-section shapes and the influence of two distinct flow conditions. The results show that the parameters of the slope-break method and satellite observation period have an inevitable impact on the accuracy of river bed elevation estimation, while the improved submerged shapes could compensate for the flaws of bed elevation estimation in the hydraulic modelling. The hydraulic models in this study are not sensitive to the flow conditions because of the simplicity of synthetic rivers. Nevertheless, the performance of hydraulic models with modified river cross-sections is more apparent in low flow conditions than in high flow conditions.
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Fournier, Mathew. "Investigations into the Shear Strength Reduction method using distinct element models." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2492.
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This thesis reports a detailed investigation into the use of the Shear Strength Reduction (SSR) method to determine factor of safety values in discontinuum models using the Universal Distinct Element Code. The SSR method depends on the definition of failure within the model and two different criteria were compared: the numerical unbalanced force definition and a more qualitative displacement-monitoring based method. A parametric study was first undertaken, using a simple homogeneous rock slope, with three different joint networks representing common kinematic states. Lessons learned from this study were then applied to a more complex case history used for validation of the SSR method.
The discontinuum models allow for the failure surface to propagate based on constitutive models that better idealize the rockmass than simpler methods such as limit equilibrium (e.g. either method of slices or wedge solutions) and even numerical continuum models (e.g. finite difference, finite element). Joints are explicitly modelled and can exert a range of influences on the SSR result. Simple elasto-plastic models are used for both the intact rock and joint properties. Strain-softening models are also discussed with respect to the SSR method. The results presented highlight several important relationships to consider related to both numerical procedures and numerical input parameters.
The case history was modelled similar to how a typical forward analysis would be undertaken: i.e. simple models with complexities added incrementally. The results for this case generally depict a rotational failure mode with a reduced factor of safety due to the presence of joints within the rockmass when compared to a traditional limit equilibrium analysis. Some models with large persistence of steeply dipping joints were able to capture the actual failure surface. Softening models were employed in order to mimic the generation and propagation of joints through the rockmass in a continuum; however, only discontinuum models using explicitly defined joints in the model were able to capture the correct failure surface.
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Brooks, Susan Mary. "Modelling the role of mass movement in slope development : the interaction between pedogenesis and hillslope hydrology." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386236.
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Bijker, Hermina Johanna. "A Hydrological-slope stability model for shallow landslide prediction in the Injisuthi Valley, KwaZulu-Natal Drakensberg." Diss., University of Pretoria, 2001. http://hdl.handle.net/2263/29748.
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Chiaravalloti, Rosario. "Numerical modelling and back analysis of a rock slope failure occurred in 2005 at Scascoli (Bologna, Italy)." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.
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The rock slope failure object of this study occurred on the 12th of March, 2005, within the Scascoli Gorges in the Savena Valley, 25 km south of Bologna, in the Northern Apennines, Italy. The failure involved a volume of rock of nearly 30000 m3 that detached from an 80 m high cliff and fell on the river bed and onto the adjacent road, denoted as “Strada Provinciale – Fondovalle Savena”, damming the first and destroying the latter. The conformation of the cliff, known as “Mammellone 1”, was rather convex, overhanging and undercut at the base where in contact with the river bed. The event is the last of a series of mass movements which occurred in a 15-year span in the area. With integration of past analyses and surveys, possible causes and mechanism of failure have been investigated by means of two and three-dimensional kinematic analysis (using the software DIPS and SWEDGE by Rocscience, 2016), photogrammetry and terrestrial laser scanning comparison (Cloud Compare, Daniel Girardeau-Montaut, 2016; Autocad, Autodesk, 2016) and two-dimensional finite element numerical modelling (RS2, Rocscience, 2016). The use of a finite element method to model a predominantly blocky structure has shown to be effective and to produce good results if data integration, boundary conditions and geometry of the site are well correlated between each other to best fit the resulting scenario. The design of the numerical model considered the relative position of crown and scarp to the discontinuity families and to the geometry of the cross section, to better costrain the failure surface. Furthermore, the process of formation of the valley was taken into account in order to consider also stress-strain conditions prior to the road construction and river erosion. This was carried out by multi-staging the modelling process considering the natural erosion and the advancement of the landslide on the hydrogeological left side of the Savena steam before the last rockfall event.
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Park, Alistair J. C. "The application of Geographical Information System approach to the modelling of tropical slope instability over wide areas." Thesis, University of Bristol, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294851.
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Sonnessa, Alberico <1975>. "Slope stability analysis by multi-temporal DEMs and 3D modelling: The 2002 and 2007 Stromboli landslide events." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2676/.
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Natural hazard related to the volcanic activity represents a potential risk factor, particularly in the vicinity of human settlements. Besides to the risk related to the explosive and effusive activity, the instability of volcanic edifices may develop into large landslides often catastrophically destructive, as shown by the collapse of the northern flank of Mount St. Helens in 1980.
A combined approach was applied to analyse slope failures that occurred at Stromboli volcano. SdF slope stability was evaluated by using high-resolution multi-temporal DTMMs and performing limit equilibrium stability analyses.
High-resolution topographical data collected with remote sensing techniques and three-dimensional slope stability analysis play a key role in understanding instability mechanism and the related risks.
Analyses carried out on the 2002–2003 and 2007 Stromboli eruptions, starting from high-resolution data acquired through airborne remote sensing surveys, permitted the estimation of the lava volumes emplaced on the SdF slope and contributed to the investigation of the link between magma emission and slope instabilities.
Limit Equilibrium analyses were performed on the 2001 and 2007 3D models, in order to simulate the slope behavior before 2002-2003 landslide event and after the 2007 eruption. Stability analyses were conducted to understand the mechanisms that controlled the slope deformations which occurred shortly after the 2007 eruption onset, involving the upper part of slope. Limit equilibrium analyses applied to both cases yielded results which are congruent with observations and monitoring data.
The results presented in this work undoubtedly indicate that hazard assessment for the island of Stromboli should take into account the fact that a new magma intrusion could lead to further destabilisation of the slope, which may be more significant than the one recently observed because it will affect an already disarranged deposit and fractured and loosened crater area.
The two-pronged approach based on the analysis of 3D multi-temporal mapping datasets and on the application of LE methods contributed to better understanding volcano flank behaviour and to be prepared to undertake actions aimed at risk mitigation.
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Hou, Xiaoping. "Composite element method for modelling transient groundwater flow in fractured media and its application to slope stability problem." Thesis, Lille 1, 2017. http://www.theses.fr/2017LIL10051/document.
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Ce travail de thèse propose un modèle numérique complet pour l'écoulement transitoire des eaux souterraines dans les milieux poreux et fracturés et son application sur l’analyse de la stabilité des pentes sous l’effet d’une diminution du niveau de l’eau dans un réservoir. L’écouement de l’eau dans les milieux fracturés est complexe, en raison de la présence d'un grand nombre de fractures et de fortes variations dans les propriétés géométriques et hydrauliques de ces milieux.La thèse est organisée en six chapitres.Le premier chapitre pésente les problèmes abordés et les objectifs de la thèse. Le 2nd chapitre présente une synthèse des analyses numériques de l'écoulement dans les milieux fracturés et de ses effets sur la stabilité des pentes. Le 3ème chapitre présente le développment d’un modèle numérique d'écoulement transitoire saturé dans des milieux fracturés avec une surface libre en utilisant la méthode des éléments composites (CEM). Le 4ème chapitre présente un modèle numérique d'écoulement transitoire à saturation variable, dans les milieux fracturés à l'aide du CEM.Le 5ème chapitre présente une étude de la stabilité des pentes sous l’effet de variation des paramètres hydrauliques et de résistance des sols, et da géométrie des pentes.Le 6ème chapitre présente une étude paramétrique de l'influence des caractéristiques de fracture sur l'écoulement transitoire et la stabilité d’une pente soumise à des conditions de diminutionThis thesis presents a comprehensive numerical method for analyzing transient groundwater flow in porous and fractured media and its application to the analysis of the stability of soil and rock slopes subjected to transient groundwater flow induced by reservoir drawdown conditions. Compared to that of porous media, the analysis of flow in fractured media is relatively complex, due to the presence of a large number of fractures and strong variations in geometric and hydraulic properties.The thesis is organized in six chapters. Chapter 1 presents the issues to be addressed and the thesis objectives. Chapter 2 discusses basic theories related to the numerical analysis of groundwater flow in fractured media and its effects on slope stability.Chapter 3 develops the numerical model of transient, saturated flow in fractured media with a free surface using the composite element method (CEM). Chapter 4 presents the numerical model of transient, variably-saturated flow in fractured media using the CEM.Chapter 5 includes an investigation of the stability of homogeneous soil slopes under drawdown conditions, depending on the drawdown rate, hydraulic and strength parameters of soils, and slope geometry.The last chapter presents a parametric study on the influence of fracture characteristics on transient flow and stability of layered rock slope subjected to drawdown conditions
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Kocal, Arman. "Three Dimensional Numerical Modelling Of Discontinuous Rocks By Using Distinct Element Method." Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610005/index.pdf.
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Shear strength characterization of discontinuities is an important concept for slope design in discontinuous rocks. This study presents the development of a methodology for implementing Barton-Bandis empirical shear strength failure criterion in three dimensional distinct element code, 3DEC, and verification of this methodology.
Normal and shear deformation characteristics of discontinuities and their relations to the discontinuity surface characteristics have been reviewed in detail.
First, a C++ dynamic link library (DLL) file was coded and embedded into 3DEC for modelling the Barton-Bandis shear strength criterion. Then, a numerically developed direct shear test model was used to verify the normal and shear deformation behaviour with respect to empirical results of the Barton-Bandis shear strength criterion.
A three dimensional simple discontinuous rock slope was modelled in 3DEC based on Barton-Bandis shear strength criterion. The slope model was first utilized by Mohr-Coulomb failure criterion. Then, with the use of the new model developed here, the effects of the discontinuity surface properties on shear strength were introduced to the slope problem.
Applicability of the developed model was verified by three large scale real case studies from different open pit lignite mines of Turkish Coal Enterprises (TKi), namely Bursa Lignites Establishment (BLi) &ndash2 cases and Ç
an Lignite Establishment (Ç
Li). The results with the new model option, which allows users to use important discontinuity surface properties like joint roughness coefficient and joint wall compressive strength, compared well with results of previous studies using Mohr-Coulomb failure criterion.
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Ekberg, Bergman Emelie. "Jämförelse av metod vid stabilitetsanalys i bergslänter." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-352090.
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En bergslänts stabilitet styrs av berggrundens egenskaper, så som sprickegenskaper och bergkvalité. För att uppnå önskad stabilitet i en bergslänt behöver de bergmekaniska parametrarna kartläggas och analyseras för att fastställa risker och stabilitetsåtgärder. Syftet med studien är att utvärdera kvalitén på bergteknisk data från digitalfotogrammetriska 3D-modeller genom att jämföra resultatet med manuella mätningar från konventionell kartläggning. Målet är även att utforska potentialen för användning av fotogrammetrisk 3D-modellering vid stabilitetsanalyser i bergslänter genom att utvärdera den bergtekniska analys som kan göras utifrån fotogrammetrisk data. Sprickmätningar framtagna från 3D-modellen visade sig ha samma kvalité som manuella mätningar tagna enligt konventionell metod. Den UAS-baserade fotogrammetrin kan dock inte ersätta den konventionella analysen helt vid stabilitetsanalyser men kan användas som ett kompletterande verktyg i bergtekniska undersökningar. Fotogrammetrin möjliggör datainsamling från ett säkrare avstånd vilket minskar riskmomenten som den konventionella metoden medför vid arbete i fält. Den digitala metoden visade sig även ha fler fördelar såsom möjligheten av kartläggning och analysering framför datorn för mindre tids- och kostnadskrävande moment, digital datalagring samt att slänter med begränsad åtkomst kan karteras.The stability of a rock slope is controlled by the rock’s mechanical properties, such as rock quality and facets. To achieve the desired stability in a rock slope, the mechanical parameters need to be mapped and analysed to determine possible failures and decide necessary stability measures. The purpose of this study is to evaluate the quality of rock technical data from digital photogrammetry 3D models by comparing the result with manual measurements from conventional mapping. The goal is also to explore the potential uses of photogrammetric 3D models for rock slope stability analyses by evaluate the photogrammetric data. Facets extracted from 3D models were found to have the same quality as manual measurements. However, the UAS-based method cannot completely replace the conventional method but can be useful as a complementary tool. Photogrammetry enables the collection of data from a safer distance, which reduces workplace hazards that the conventional method entails. The digital method also proved to have more advantages, such as the possibility of digital mapping and analysing which is less costly and time-consuming, digital data storage and the possibility to access outcrops that can’t be mapped with manually measurements due to inaccessibility.
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Chapman, Neil. "Modelling the dynamic interaction between hydrology, slope stability and wave run-up processes in the soft-sea cliffs at Covehithe, Suffolk, UK." Thesis, Birkbeck (University of London), 2014. http://bbktheses.da.ulcc.ac.uk/98/.
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Soft-rock coastal cliff retreat progresses by an intermittent and discontinuous series of slope mass movements, generally accepted to be concentrated during phases of strong wave attack or heavy rain. One of the fundamental limitations to improving understanding of these processes is a lack of accurate quantitative data on the hydrological and geotechnical behaviour of the cliff slope. In this study, high-resolution terrestrial surveys of coastal change over a fifteen year period have been analysed and combined with hydrological and geotechnical simulations of cliff behaviour under rainfall stress. The input parameters for the simulations have been established from site survey, cross-checked with data from a range of published literature. The numerical model has been applied to typical hydrological, climatic and geotechnical conditions at Covehithe, Suffolk. In addition, analyses of water levels and beach elevations have subsequently been included using archive observation data, to further investigate the mechanisms governing the nature of change at the study site. Key findings include: (a.) high-resolution modelling of rainfall-infiltration processes combined with slope stability analysis provides a unique insight into the complex interaction between slope morphology and dynamic hydrology in soft sea cliffs. (b.) detailed analysis of daily factors of safety related to specific daily rainfalls is significant in reproducing failure conditions at the study site, and elucidates the complex interaction between cliff stratigraphy, cliff hydrology and rainfall. (c.) The results of the water level and beach elevation analyses show that marine processes are significant to the generation of cliff instability, consistent with the field observations and with the Sunamura (1983) model. These findings suggest that the instability of soft sea-cliffs results from complex and interacting controls that require an approach utilising a fully integrated transient hydrology and slope stability modelling. These results have significant implications for current coastal management practice.
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Ji, Jinnan. "Finite elements modelling and analysis of the effect of vegetation on forested slopes stability." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20213.
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L'ingénierie écologique, qui est décrite comme «la gestion de la nature», a d'abord été proposée par Odum en 1971. Dans les dernières décennies, l'ingénierie écologique a été largement consacrée à lutter contre l'érosion des sols et les mouvements de masse, tout en permettant d'assurer la durabilité des écosystèmes. L'objectif de cette thèse est d'évaluer l'impact de peuplements forestiers sur la stabilité de pentes de dimension finie, en considérant à la fois les effets mécaniques et hydrologiques des racines peu profondes contre les glissements de terrain. Deux sites forestiers monospécifiques et équiennes, plantés respectivement de Robinia pseudoacacia et Platycladus orientalis, ont été sélectionnés sur le Plateau du Loess en Chine et utilisés comme sites d'étude. Le Facteur de Sécurité (FoS) de ces pentes ont été calculées en utilisant un modèle éléments finis 2D qui prend en compte la distribution des racines dans les couches superficielles du sol.Des mesures de terrain et des tests de laboratoire ont été effectués afin d'estimer les principaux paramètres du modèle, à savoir la distribution des surfaces relatives de racines dans le sol (Root Area Ratio), la résistance à la traction des racines, ainsi que les propriétés mécaniques et hydrologiques du sol nu. La contribution des racines à la résistance au cisaillement du sol a été considérée par l'intermédiaire d'une « cohésion additionnelle » calculée à l'aide de modèles fournis par la littérature. Six modèles existants ont été testés. Cette thèse est composée de deux chapitres principaux portant sur: (1) l'effet mécanique de l'hétérogénéité spatiale de la distribution des racines à l'échelle de pente; (2) l'influence de la distribution des racines sur le couplage entre la diffusion de l'eau interstitiel et les contraintes mécaniques dans le sol et son impact sur la stabilité des pentes.Les simulations amènent aux conclusions principales suivantes: (1) les pentes en terrasse sont en théorie 20% plus stables que les pentes rectilignes, sans tenir compte des effets hydrologiques; (2) le FoS atteint une valeur asymptotique lorsque l'on augmente la cohésion des racines; (3) les variations de la cohésion des racines observées sur le terrain ont peu d'effet sur la stabilité des pentes. Toutefois le renforcement de la partie basse des pentes, où les racines ont un plus grand impact positif sur le FOS, peut permettre de diminuer le risque de glissement; (4) l'effet des fortes précipitations sur la stabilité de la pente pourrait probablement être atténué par la présence de racines, mais cet effet dépend des caractéristiques des racines et de leur influence sur le débit d'eau dans le solEcological engineering, which is described as ‘the management of nature', was first proposed by Odum in 1971. In the past few decades, ecological engineering has been largely devoted to combat soil erosion and mass movement all over the world, because of its benefit on sustainable ecosystems. The objective of this thesis is to evaluate the impact of forest stands on the stability of finite slopes, considering both the mechanical and hydrological effects of roots against shallow landslides. Two monospecific and even-aged forest sites planted with Robinia pseudoacacia and Platycladus orientalis respectively were selected on the Loess Plateau of China and used as study sites. Slope Factors of Safety were calculated using a 2D finite element model that takes into account the distribution of roots in the shallow layers of soil.Field site experiments and laboratory tests were performed in order to estimate the main parameters of the model, i.e. distribution of root area ratio within the soil, root tensile strength, as well as bare soil mechanical and hydrological properties. The contribution of roots to soil shear strength was considered through an additional cohesion calculated with models provided by the literature. Six existing models were tested. This thesis is composed of two main chapters that make the focus on : (1) the mechanical effect of the spatial heterogeneity of root distribution at the slope scale; (2) the influence of root distribution on the coupling between pore fluid diffusion and mechanical stress and its impact on slope stability. This study brings to the following main conclusions: (1) terraced slopes were 20% more stable than rectilinear slopes, disregarding the differences in hydrological regimes between the two sites; (2) FoS could reach an asymptotic value when increasing root additional cohesion; (3) variations of the actual root cohesion do not affect much slope stability. However more attention should be given to the reinforcement of the bottom part of the actual slopes, where roots have a larger positive impact on the FoS; (4) the effect of heavy precipitations on slope stability could probably be overcome or at least mitigated by root system network, but this depends on root characteristics and their resulting effect on soil water flow
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Andersson, Elin, and Sofia Hietala. "Application of a new method to improve river cross sections derived from satellite images." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-242553.
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In hydrological and hydraulic modelling, river geometry is a crucial input data. Recent investigations have been looking at methods to improve the description of cross sections extracted by DEM derived by satellite images. SRTM derived DEM are often lacking precise information as the sensors cannot detect the submerged river parts, but, on the other hand, it is available on a global scale which makes it very attractive and useful, especially in data scarce regions. This study aims at applying the so called “slope break” method to improve river cross section geometry extracted from SRTM DEM. The report is divided into three parts: a) The making of a Matlab-code to improve cross sections geometry extracted by satellite derived DEM; b) an application of the code to real cross-sections from the river Po in Italy and c) hydraulic simulations with and without SRTM modified cross sections to test the performance of the method, in collaboration with senior colleagues. The Matlab successfully performs the slope break point and finds, when appropriate, the approximated lowest point zmin of the cross section below the water surface. The comparison of the river geometry of the modified SRTM cross sections versus LiDAR available cross sections show the good performance of the method in improving the river geometry description. This code can simplify the work and improve many SRTM river cross sections in an effective way. The hydraulic simulations performed with and without the modified cross sections show how the modified SRTM model improves when compared to LiDAR results
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Moura, Nícolas Rodrigues. "Contribution to the study of the effect of three-dimensional stress states to slope stability analysis." Universidade Federal de Goiás, 2018. http://repositorio.bc.ufg.br/tede/handle/tede/8904.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Análises de estabilidade de taludes são predominantemente realizadas em duas-dimensões (2D) por métodos de equilíbrio limite. Os métodos convencionais de equilíbrio limite são alvos de muitas críticas pelo o uso do equilíbrio estático, pressuposições de forças na análise e por possuir o mesmo fator de segurança ao longo de toda a superfície de deslizamento. Para superar essas deficiências, o método proposto por Kulhawy (1969) incorpora o comportamento tensão-deformação do solo com tensões oriundas do Método de Elementos Finitos (FEM) e tem a mesma estrutura dos métodos de equilíbrio dos métodos de equilíbrio de equilíbrio limite clássicos. É também chamado de método aperfeiçoado. Devido à existência de taludes com geometrias complexas, a abordagem tridimensional (3D) é a única capaz de incorporar todos os aspectos geométricos do problema. Esta dissertação é dividida em dois artigos com o tema de estabilidade de taludes pelo o método de Kulhawy em abordagens 2D e 3D. O objetivo primário dessa dissertação é avaliar os principais fatores que influenciam a estabilidade de taludes. O primeiro artigo propôs geometrias variando de convexo a côncavo em um conjunto de propriedades típicas de solos. Duas trajetórias de geração de tensões in- situ foram utilizadas, i.e., construção e escavação. O método GLE foi calculado para fins de comparação. A superfície de deslizamento é muito dependente do histórico de tensão e da forma da face do talude. A diferença relativa no estado de tensões inicial típico alcançou 15% nas análises 2D e 34% nas análises 3D. A análise de sensibilidade do efeito do Poisson no fator de segurança mostrou-se muito relevante. A relação entre os fatores de segurança 2D e 3D são quase lineares independente do estado de tensões, das propriedades de resistência, formato da face do talude, na ordem de 30 a 40%. O segundo artigo propõe análises em barragens construídas em vales estreitos. Três abordagens de análises foram utilizadas: redução de resistência ao cisalhamento (SSR), métodos de Kulhawy e GLE. Condições típicas de fundações são muito variáveis como topografia e deformabilidade. A análise de sensibilidade do módulo de fundação de Young no fator de segurança foi insignificante em 2D e relevantes em 3D. A relação entre o comprimento do aterro (W) e a altura () é uma variável representativa do grau de estreitamento da barragem e na estabilidade de taludes. A análise de deformações planas tende a altas relações W/H e o oposto mostra elevados efeitos 3D. A inclinação da ombreira mostrou-se relevante no fator de segurança apenas em aterros em vales estreitos. Fundações mais rígidas são mais beneficias para o fator de segurança devido à produção de altos efeitos de arqueamento neste cenário. O método de Kulhawy provou-se ser vantajoso pela a incorporação do comportamento mecânico do solo, o uso de tensões mais realísticas nas análises e avaliação da estabilidade local na superfície de deslizamento. Isso aumenta a quantidade de informações úteis e confiáveis para o profissional de engenharia no projeto de taludes. Todas as análises foram realizadas usando o software SoilVision Systems, Saskatchewan, Canadá. Os módulos utilizados foram o SVLOPE, SVSOLID e o SVFLUX (SoilVision Systems Ltd., 2018). A análise de tensão para a simulação de trajetórias de escavação e construção utilizou do solucionador de Equações Diferenciais Parcias (PDE) o FlexPDE 6 (PDE Solutions Inc., 2014).
Slope stability analyses are predominantly performed using the two-dimensional (2D) conventional limit equilibrium methods. Conventional limit equilibrium methods are targets of many criticisms for using static equilibrium, assumptions of forces in the analysis and the same factor of safety along the slip surface. In order to overcome these shortcomings, the method proposed by Kulhawy (1969) incorporates the stress-strain behavior of the soil with stresses from the Finite Element Method (FEM) with the same structure as limit equilibrium methods. It is also called enhanced method. Due to the existence of slopes with complex geometries, the three-dimensional (3D) approach is only able to incorporate all the geometric aspects of the problem. This thesis is divided into two papers with the subject of slope stability analyses by the Kulhawy’s method in 2D and 3D approaches. The primary objective of this thesis is to evaluate major factors that influence slope stability. The first paper proposed geometries ranging from convex to concave in a set of soil properties. Two stress paths were considered, i.e., construction and excavation. The GLE method was computed for comparison purposes. The slip surface is very dependent on the stress history and the shape of slope face. The relative difference in typical initial stress state reached 15% in 2D analyses and 34% in 3D analyses. Sensitivity analysis of effect of Poisson’s ratio on factor of safety was very relevant. The relationship between 2D and 3D factors of safety are nearly linear independent of stress state on order of 30 to 40%. The second paper propose analyses on embankment dams built in narrow valleys. Three approaches of slope stability were used: shear strength reduction (SSR), Kulhawy’s and GLE methods. The typical conditions of foundation sites are very variable as topography and deformability. Sensitivity analysis of Young’s modulus of foundation on factor of safety was insignificant in 2D and relevant in 3D analyses. The ratio between embankment length (W) and height (H) was very important on slope stability. The plane strain analysis tends to high W/H ratio and the opposite shows high 3D effects. The inclination of abutment showed to be relevant on factor of safety only in embankments in narrow valleys. Stiffer foundations are beneficial to the factor of safety due producing high arching effects in this scenario. The Kulhawy’s method proved to be advantageous by the incorporation of mechanical behavior of soil, more realistic stress and local stability evaluation on slip surface. It increases the amount of useful and reliable information to the engineering professional in design of slopes. All analyses were performed using SoilVision Systems suite software, Saskatchewan, Canada. The modules used were SVSLOPE, SVSOLID and SVFLUX (SoilVision Systems Ltd., 2018). The stress analysis for the simulation of excavation and construction trajectories used partial differential equation (PDE) solver, FlexPDE 6 (PDE Solutions Inc., 2014).
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Pedley, Katherine Louise. "Modelling Submarine Landscape Evolution in Response to Subduction Processes, Northern Hikurangi Margin, New Zealand." Thesis, University of Canterbury. Geological Sciences, 2010. http://hdl.handle.net/10092/4648.
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The steep forearc slope along the northern sector of the obliquely convergent Hikurangi subduction zone is characteristic of non-accretionary and tectonically eroding continental margins, with reduced sediment supply in the trench relative to further south, and the presence of seamount relief on the Hikurangi Plateau. These seamounts influence the subduction process and the structurally-driven geomorphic development of the over-riding margin of the Australian Plate frontal wedge.
The Poverty Indentation represents an unusual, especially challenging and therefore exciting location to investigate the tectonic and eustatic effects on this sedimentary system because of: (i) the geometry and obliquity of the subducting seamounts; (ii) the influence of multiple repeated seamount impacts; (iii) the effects of structurally-driven over-steeping and associated widespread occurrence of gravitational collapse and mass movements; and (iv) the development of a large canyon system down the axis of the indentation. High quality bathymetric and backscatter images of the Poverty Indentation submarine re-entrant across the northern part of the Hikurangi margin were obtained by scientists from the National Institute of Water and Atmospheric Research (NIWA) (Lewis, 2001) using a SIMRAD EM300 multibeam swath-mapping system, hull-mounted on NIWA’s research vessel Tangaroa. The entire accretionary slope of the re-entrant was mapped, at depths ranging from 100 to 3500 metres. The level of seafloor morphologic resolution is comparable with some of the most detailed Digital Elevation Maps (DEM) onshore. The detailed digital swath images are complemented by the availability of excellent high-quality processed multi-channel seismic reflection data, single channel high-resolution 3.5 kHz seismic reflection data, as well as core samples. Combined, these data support this study of the complex interactions of tectonic deformation with slope sedimentary processes and slope submarine geomorphic evolution at a convergent margin.
The origin of the Poverty Indentation, on the inboard trench-slope at the transition from the northern to central sectors of the Hikurangi margin, is attributed to multiple seamount impacts over the last c. 2 Myr period. This has been accompanied by canyon incision, thrust fault propagation into the trench fill, and numerous large-scale gravitational collapse structures with multiple debris flow and avalanche deposits ranging in down-slope length from a few hundred metres to more than 40 km. The indentation is directly offshore of the Waipaoa River which is currently estimated to have a high sediment yield into the marine system. The indentation is recognised as the “Sink” for sediments derived from the Waipaoa River catchment, one of two target river systems chosen for the US National Science Foundation (NSF)-funded MARGINS “Source-to-Sink” initiative. The Poverty Canyon stretches 70 km from the continental shelf edge directly offshore from the Waipaoa to the trench floor, incising into the axis of the indentation. The sediment delivered to the margin from the Waipaoa catchment and elsewhere during sea-level high-stands, including the Holocene, has remained largely trapped in a large depocentre on the Poverty shelf, while during low-stand cycles, sediment bypassed the shelf to develop a prograding clinoform sequence out onto the upper slope. The formation of the indentation and the development of the upper branches of the Poverty Canyon system have led to the progressive removal of a substantial part of this prograding wedge by mass movements and gully incision. Sediment has also accumulated in the head of the Poverty Canyon and episodic mass flows contribute significantly to continued modification of the indentation by driving canyon incision and triggering instability in the adjacent slopes.
Prograding clinoforms lying seaward of active faults beneath the shelf, and overlying a buried inactive thrust system beneath the upper slope, reveal a history of deformation accompanied by the creation of accommodation space. There is some more recent activity on shelf faults (i.e. Lachlan Fault) and at the transition into the lower margin, but reduced (~2 %) or no evidence of recent deformation for the majority of the upper to mid-slope. This is in contrast to current activity (approximately 24 to 47% shortening) across the lower slope and frontal wedge regions of the indentation. The middle to lower Poverty Canyon represents a structural transition zone within the indentation coincident with the indentation axis. The lower to mid-slope south of the canyon conforms more closely to a classic accretionary slope deformation style with a series of east-facing thrust-propagated asymmetric anticlines separated by early-stage slope basins. North of the canyon system, sediment starvation and seamount impact has resulted in frontal tectonic erosion associated with the development of an over-steepened lower to mid-slope margin, fault reactivation and structural inversion and over-printing.
Evidence points to at least three main seamount subduction events within the Poverty Indentation, each with different margin responses:
i) older substantial seamount impact that drove the first-order perturbation in the margin, since approximately ~1-2 Ma
ii) subducted seamount(s) now beneath Pantin and Paritu Ridge complexes, initially impacting on the margin approximately ~0.5 Ma, and
iii) incipient seamount subduction of the Puke Seamount at the current deformation front.
The overall geometry and geomorphology of the wider indentation appears to conform to the geometry accompanying the structure observed in sandbox models after the seamount has passed completely through the deformation front. The main morphological features correlating with sandbox models include: i) the axial re-entrant down which the Poverty Canyon now incises; ii) the re-establishment of an accretionary wedge to the south of the indentation axis, accompanied by out-stepping, deformation front propagation into the trench fill sequence, particularly towards the mouth of the canyon; iii) the linear north margin of the indentation with respect to the more arcuate shape of the southern accretionary wedge; and, iv) the set of faults cutting obliquely across the deformation front near the mouth of the canyon. Many of the observed structural and geomorphic features of the Poverty Indentation also correlate well both with other sediment-rich convergent margins where seamount subduction is prevalent particularly the Nankai and Sumatra margins, and the sediment-starved Costa Rican margin. While submarine canyon systems are certainly present on other convergent margins undergoing seamount subduction there appears to be no other documented shelf to trench extending canyon system developing in the axis of such a re-entrant, as is dominating the Poverty Indentation.
Ongoing modification of the Indentation appears to be driven by: i) continued smaller seamount impacts at the deformation front, and currently subducting beneath the mid-lower slope, ii) low and high sea-level stands accompanied by variations on sediment flux from the continental shelf, iii) over-steepening of the deformation front and mass movement, particularly from the shelf edge and upper slope.
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Al-Defae, Asad Hafudh Humaish. "Seismic performance of pile-reinforced slopes." Thesis, University of Dundee, 2013. https://discovery.dundee.ac.uk/en/studentTheses/829dd554-a7e9-4c61-9206-01909793666c.
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Shallow embankment slopes are commonly used to support elements of transport infrastructure in seismic regions. In this thesis, the seismic performance of such slopes in non-liquefiable granular soils has been investigated and an extensive programme of centrifuge testing was conducted to quantify the improvements to seismic slope performance which can be achieved by installing a row of discretely spaced vertical precast concrete piles. This study focussed on permanent movement and dynamic response at different positions within the slope, especially at the crest, which would form key inputs into the aseismic design of supported infrastructure. In contrast to previous studies, the evolution of this behaviour under multiple sequential strong ground motions is studied through dynamic centrifuge modelling, analytical (sliding-block) and numerical (Finite Element) models. This thesis makes three major contributions. Firstly, an improved sliding-block (‘Newmark’) approach is developed for estimating permanent deformations of unreinforced slopes during preliminary design phases, in which the formulation of the yield acceleration is fully strain-dependent, incorporating the effects of both material hardening/softening and geometric hardening (re-grading). This is supported by the development of numerical (Finite Element) models which can additionally predict the settlement profile at the crest of the slope and also the dynamic ground motions at this point, for detailed seismic design were also developed. It is shown that these new models considerably outperform existing state-of-the art models which do not incorporate the geometric changes for the case of an earthquake on a virgin slope. It is further shown that only the improved models can correctly capture the behaviour under further earthquakes (e.g. strong aftershocks) and therefore can be used to determine the whole-life performance of a slope under a suite of representative ground motions that the slope may see during its design life, and allow improved estimates of the seismic performance of slopes beyond their design life. The finite element models can accurately replicate the settlement profile at the crest (important for highway or rail infrastructure) and quantify the dynamic motions which would be input to supported structures, though these were generally over-predicted. Secondly, the principles of physical modelling have been used to produce realistically damageable model piles using a new model reinforced concrete (both a designed section specifically detailed to carry the bending moments induced by the slipping soil mass and a nominally reinforced section with low moment capacity). This was used to investigate how piles can stabilise slopes under earthquake events and how the permanent deformation and the dynamic response of stabilised slope are strongly influenced by the pile spacing (S/B) especially at the minimum pile spacing (i.e. S/B=3.5). This is consistent with previous suggestions made for the optimal S/B ratio for encouraging soil arching between piles at maximum spacing both under monotonic conditions, and for numerical investigations of the seismic problem. These were supported by further centrifuge tests on conventional ‘elastic’ piles which were instrumented to measure seismic soil-pile interaction. The importance of reinforcement detailing was also highlighted, with the nominally reinforced section yielding early in the earthquake; the damaged piles subsequently only offer a small (though measureable) reduction in seismic slope performance compared to the unreinforced case. It was demonstrated that both permanent deformations at the slope crest (e.g. settlement) and dynamic ground motions at the crest can be significantly reduced as pile spacing reduced. Finally, a coupled P-y and elastic continuum approach for modelling soil-pile interaction has been used to develop a Newmark procedure applicable for pile-reinforced slopes. It was observed that the single pile resistance is mobilising at beginning of the earthquake’s time and it is strongly influenced by pile stiffness properties, pile spacing and the depth of the slip surface. It was observed also that the depth of the slip surface and pile spacing (S/B) play an important role in the determination of the permanent deformation of the slope. The results show great agreement to centrifuge test data in term of the permanent deformation (settlement at the crest of the slope) with slight differences between the measured (centrifuge) and calculated (this procedure) maximum bending moments.
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Mohd, Taib Aizat Bin. "Numerical modelling of unsaturated tropical slopes." Thesis, University of Newcastle upon Tyne, 2018. http://hdl.handle.net/10443/4153.
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Adapting to climate change is one of the greatest challenges facing engineers. Many studies have been conducted since the 1900s directed at predicting extreme weather events. Changes in global weather patterns, such as temperature and rainfall distributions, can have major economic and societal impacts. One example, addressed in this thesis, is the stability of natural slopes. In Southeast Asia, landslides are common due to the effect of abundant rainfall during the wet monsoon. The local climate in the region is characterised by annual wet and dry seasons, in which the cycle forms an unsaturated zone at the surface of the slopes. However, as a result of climate change, prolonged drying and heavy rainfall are observed that may exacerbate slope failure particularly in unsaturated soils. The prediction and mitigation of slope failures are consequently major challenges due to the complexity of the unsaturated behaviour of tropical soils subjected to irregular weather changes. This thesis develops a methodology to model unsaturated slope behaviour taking into account the effects of climate change. The approach includes groundwater flow, soil deformation and stability analyses using a finite element method and climate change predictions to incorporate future weather scenarios. The method was established by validating the groundwater flow analysis by involving a case study in Zaoyang, China. Subsequently, a more complex case study of a tropical unsaturated slope in Bukit Timah, Singapore was also considered to calibrate the soil-water characteristic curves (SWCC), a major controlling factor in unsaturated soils mechanics. The coupled flow-deformation analysis was undertaken on the validated case studies to predict soil displacement. In addition, a parametric study was conducted to critically analyse the effects of void ratio, saturated permeability, hysteretic SWCC, soil elasticity and rainfall intensity regarding slope behaviour. Finally, statistical analysis was performed to predict the impact of climate change on the rainfall distribution in Singapore up to the year 2100 by using the historical data from 1980 to 2010. Frequency analysis was adopted to estimate the rainfall return period. The results of the future extreme rainfall were compared to predictions by the Met Office in Singapore and the United Kingdom. The effects of climate change on slope behaviour was assessed by applying the predicted climate in the slope models. The outcomes reveal that the modelling approach is able to capture groundwater flow, slope deformation and safety factor accurately under extreme weather scenarios.
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Piton, Guillaume. "Sediment transport control by check dams and open check dams in Alpine torrents." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAU041/document.
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Barrages de corrections torrentielles et plages de dépôts jouent un rôle clés dans la protection contre les crues des torrents. Leurs gestionnaires ont pour mission de réduire les risques d'inondations, mais doivent désormais aussi minimiser les impacts environnementaux liés aux ouvrages de protection. Ceci nécessite une meilleure compréhension des effets des barrages de corrections torrentielles et des plages de dépôts sur le transport sédimentaire des torrents. Cette thèse s'inscrit dans cet objectif et se décompose en deux parties. Sa section sur l'état de l'art présente: i) les différents effets des barrages de correction torrentielle sur la production et le transfert sédimentaire; ii) des descriptions des processus hydrauliques et de sédimentation ayant lieu dans les plages de dépôts; et iii) les processus liés à la production et au transfert de bois d'embâcle. Une nouvelle méthode de quantification de la production sédimentaire des torrents complète cet état de l’art.La seconde partie de cette thèse présente le travail réalisé en banc d’essai expérimental. Une première série d’expérience a permis de mettre en évidence un transport par charriage plus régulier lorsque des barrages de correction torrentielle sont ajoutés à un bief alluvial. Une seconde série d’essais a été réalisée sur un modèle générique de plage de dépôt dans l’objectif d’en caractériser les écoulements. Pour cela, une nouvelle procédure de mesure et de reconstruction par approche inverse a été développée. Il en résulte une description des caractéristiques d’un écoulement proche du régime critique, ainsi que des mécanismes de rétrocontrôle entre morphologie et hydraulique pendant la phase de dépôtCheck dams and open check dams are key structures in torrent hazard protection. Their managers must mitigate flood hazards, but now must also minimize the environmental impacts of these protection structures. This requires to improve the knowledge on the effects of check dams and open check dams on the sediment transport, and this thesis forms a contribution towards this end.The section on the current state of research reviews i) the diverse effects of check dams on sediment production and transfer; ii) descriptions of the hydraulics and sedimentation processes occurring in open check dams; and iii) woody debris production and trapping processes. This state of the art is completed with proposition of new bedload transport estimation methods, specifically developed for paved streams experiencing external supply or armour breaking.Experimental results are then provided. Firstly, flume experiments highlight the emergence of a more regular bedload transport when check dams are built in alluvial reaches. In a second stage, experiments were performed on a generic Froude scale model of an open check dam basin in order to capture the features of laterally-unconstrained, highly mobile flows. A new flow measurement and inverse-reconstruction procedure has been developed. A preliminary analysis of the results describes flows that tend toward a critical regime and the occurrence of feedback mechanisms between geomorphology and hydraulics during massive bedload deposition
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Liang, Teng. "Seismic performance of vegetated slopes." Thesis, University of Dundee, 2015. https://discovery.dundee.ac.uk/en/studentTheses/04c95230-9768-4c0a-8b8a-b32081d039a9.
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Payne, Gregory Sebastien. "Numerical modelling of a sloped wave energy device." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/15607.
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Computer based numerical prediction of wave-body interactions has become a powerful design tool and is widely used in the offshore industry. Its application to wave energy conversion is more recent. The present work investigates the modelling of three configurations of sloped wave energy converters of increasing complexity using the boundary element method package WAMIT. These configurations are all related to the concept of the Sloped IPS buoy wave energy device. In order to understand and assess the validity of numerical modelling for the specific cases considered, a two stage procedure is adopted. The first stage is to check that the results obtained from WAMIT are consistent with its underlying theory. These results are then compared with the corresponding experimental data. The experimental equipment and methodology are described. This includes discussion of wave tanks, models, and measuring techniques. The three configurations of wave energy converter investigated are the following: (a) a single degree of freedom system whose power take-off is referenced to the sea bed; (b) a free floating device with no power take-off; and (c) a free floating device fitted wit a power take-off mechanism that uses water inertia for its reference.
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Fernandes, Mariana Alher. "Estudo dos mecanismos de instabilização em um talude de solo arenoso não saturado localizado na região Centro-Oeste Paulista." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/18/18132/tde-28112016-093540/.
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A presença de encostas com solos na condição não saturada é muito comum na região Sudeste brasileira devida às características climáticas e hidrogeológicas regional. Neste caso, o mecanismo de instabilização pode ser basicamente descrito pela redução da coesão aparente provocada pela infiltração da água da chuva, causada pela diminuição ou até mesmo a anulação dos efeitos da sucção matricial, tornando o talude instável. O presente trabalho apresenta um estudo dos mecanismos instabilizadores em um talude de corte composto por solo residual arenoso localizado na Rodovia Luis Augusto de Oliveira (SP-215) no km 179+300 LE, próximo ao município de Ribeirão Bonito, Brasil. Neste trabalho foi realizado um levantamento dos dados e das propriedades do solo (física, mecânica e hidráulica) da área piloto utilizando métodos de investigação geológico-geotécnica de superfície (levantamento topográfico de detalhe, caminhamentos) e de subsuperfície (sondagem a trado e poços com coleta de amostras); ensaios de laboratório e de campo (índices físicos do solo, resistência ao cisalhamento, permeabilidade); instrumentação e monitoramento (piezômetro, pluviômetro e tensiômetro) e modelagem numérica (análises da infiltração da água da chuva e de estabilidade de talude). Na área investigada ocorrem solos residuais dos arenitos eólicos da Formação Botucatu (Grupo São Bento, Bacia Sedimentar do Paraná) de idade jurássico-cretácea. As modelagens numéricas realizadas no programa GeoStudio versão 2012 (Seep/W e Slope/W) confirmaram que é possível ocorrer deslizamentos rasos de solo somente pela redução da sucção e perda de coesão aparente. As modelagens do fluxo da água infiltrada no talude apresentaram resultados divergentes das leituras registradas pelos tensiômetros instalados no talude monitorado e os fatores de segurança mostraram serem bem superiores ao unitário, mesmo ocorrendo chuvas de alta intensidade pluviométrica. Estas modelagens numéricas também permitiram estabelecer a configuração geométrica crítica (altura e inclinação) para os taludes de corte em solo residual arenoso da Formação Botucatu.The presence of slopes with soil in the unsaturated condition is very common in Brazil\'s Southeast region due to climate and regional hydrogeological characteristics. In this case, the instability mechanism can be basically described by the apparent cohesion loss caused by the rainfall infiltration that induced by the reduction or even annulling the effect of matric suction, making the slope conditionally unstable. This paper presents a study of instabilizing mechanisms in a cut slope composed of sandy residual soil located on Highway Luis Augusto de Oliveira (SP-215) at km 179 + 300 LE, near Ribeirão Bonito, Brazil. This work was carried out a survey of the data and soil properties (physical, mechanical and hydraulic) of pilot area using geological and geotechnical research techniques of surface (topographic survey) and subsurface (soil sampling and hand auger drilling); laboratory and field tests (physical indices soil, shear strength, permeability); instrumentation and monitoring (piezometer, rain gauge and tensiometer) and numerical modelling (analysis of rainfall infiltration and slope stability). In the investigated area occur residual soils of aeolian sandstones of Botucatu Formation (São Bento Group, Paraná Sedimentary Basin) Jurassic- Cretaceous age. The numerical modelling performed in GeoStudio version 2012 (Seep/W and Slope/W) confirmed that it is possible to have shallow soil slips just reducing the suction loss and apparent cohesion. The modelling of the infiltrated water flow on the slope showed conflicting results of the readings recorded by tensiometers installed on the monitored slope and the safety factors shown to be well above the unit, even occurring high intensity rainfall. These numerical models also allowed to establish the geometric critical configuration (height and slope angle) for cut slopes in a sandy residual soil of Botucatu Formation.
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Yoon, Boung Shik. "Centrifuge modelling of discrete pile rows to stabilise slopes." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/28510/.
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Discrete pile rows are widely used for improving the stability of potentially unstable slopes, where columns of reinforced concrete are constructed in the ground to reinforce it and inhibit instability. The method becomes more cost effective with wider pile spacings, but simultaneously there is also increasing risk that the soil will flow through the gap between adjacent piles, rather than arching across it. The impact of pile spacing along the row, which is likely to have a significant effect on stability, is not clearly understood from a current design perspective. In this study the effects of pile spacing on passive interaction with the slope are investigated using a series of geotechnical centrifuge model tests which are interpreted with a proposed theoretical framework. A total of 23 geotechnical centrifuge model tests were successfully carried out (Chapters 3 and 4): • A plane strain model slope was subjected to up to 50 g centrifugal acceleration, with the upper layer of the slope tending to fail on an underlying predefined surface. The model piles were instrumented to measure bending moment, and hence the shear force and pressure on the piles resulting from interaction with the unstable layer were deduced using a curve-fitting technique. Cameras ‘on-board’ the centrifuge model allowed in-flight photogrammetry to be used to determine soil or pile displacement. • Pile spacing (s/d) was varied, which determined limiting pile-soil interaction for the row, and variation of other geometrical parameters (l/h) for the slope controlled the total load on the pile row. • A number of mechanisms of behaviour for the reinforced slope were identified ranging from a successfully stabilised slope to shallow and deeper slips passing through the pile row, as well as slips which occurred upslope of the pile row and thus did not interact with it. A theoretical framework was developed and used to interpret the results (Chapter 5): • The centrifuge model test results have been successfully interpreted using the proposed analytical approach. • The centrifuge test results confirm previous numerical modelling results, and hence a simple theory which can be used for calculation of the maximum stabilising force available from interaction of the pile row with the slope. The work presented here also confirmed that another previous theoretical model, although quite widely used, is somewhat flawed. Comparison with a field study where stabilisation has been successful (to date) indicated consistency with the experimental results and associated interpretation.
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Durrani, Imran K. "Numerical modelling of discrete pile rows to stabilise slopes." Thesis, University of Nottingham, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438556.
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Lloyd, David M. "Modelling the hydrology and stability of tropical cut slopes." Thesis, University of Bristol, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303762.
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Whadcoat, Siobhan Kathleen. "Numerical modelling of rockfall evolution in hard rock slopes." Thesis, Durham University, 2017. http://etheses.dur.ac.uk/11994/.
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The aim of this thesis has been to model small rockfalls in order to better understand where, when and why they occur. High-resolution monitoring of rock slopes has revealed clustering of rockfalls through space and time, suggesting interactions, whereby one detachment from a rock slope influences the nature of those that follow. This observation contrasts with the more conventional idea of rockfalls as time-independent, discrete events that occur in response to an identifiable trigger. As the processes that give rise to observations of rockfall clustering are not well established, this thesis takes the opportunity to bring together current understanding of the controls on rockfalls with ideas around the progressive development of failure in brittle rock in an attempt to explain these patterns. The representation of these processes at scales comparable to high resolution field monitoring has not previously been attempted. Therefore this thesis has developed an approach using numerical modelling to simulate rockfalls as spatially and temporally-dependent sequences of events, to better explain the underlying mechanisms. This study begins with the analysis of a high-resolution inventory of rockfalls, concentrating on identifying patterns in rockfall occurrence. Analyses of this data reveals patterns of rockfalls that cannot be explained by environmental conditions or local geology alone. Evidence has been collected that demonstrates that rockfalls cluster in space and time, and that through time rockfall scars grow upward and outward in a consistent manner. The results of this analysis are used to inform numerical modelling that explores the mechanics driving small rockfalls, focussing upon the impact of a detachment on the location and timing of future rockfalls. Numerical modelling of idealised rock slope sections was conducted using Slope Model and demonstrated that the timing and location of failure in a rock slope could be considered as a function of accumulated damage, represented by fracture. The results suggest that time-dependent failure and associated mechanisms of stress redistribution and damage generation are one possible explanation for the propagating sequences of contiguous failures observed. Finally, this thesis has taken an exploratory approach to modelling rockfalls through the development of a new deterministic, numerical model that simulates rockfall evolution using cellular automata. This rockfall model allows the patterns and associated underlying mechanics of small rockfalls to be explored in detail using a reduced complexity approach. Critically rockfalls are modelled in a 2.5D slope face perspective to allow both rockfalls and their effects to interact across the rock slope through time. The model operates at a relatively high spatial and temporal resolution to consider the full range of rockfall characteristics that have been observed. The outputs of the model are compared with the two-year monitoring data to address key questions regarding the competing roles of endo- and exogenic forcing on rockfall occurrence. The results of the rockfall modelling shows that a consideration of stress redistribution from small scale rockfalls and time-dependent weakening provides a possible explanation for the size distribution of rockfalls, their location and timing, and the resulting changes to slope profile form as observed in the field. This has implications for how rock slopes are monitored and modelled to determine the potential for future rockfalls to occur.
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Hu, Lianxin. "Micromechanics of granular materials : Modeling anisotropy by a hyperelastic-plastic model." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI133.
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Afin de modéliser le comportement des géométariaux sous des charges complexes, plusieurs études et travaux expérimentaux ont été réalisées afin d’établir des modèles constitutifs relatifs. Une caractéristique importante des matériaux granulaires est que la relation entre la contrainte et la déformation et ce même dans le domaine élastique n’est pas linéaire, contrairement aux réponses du métal. Il a également été constaté que la réponse contrainte-déformation des matériaux granulaires montre les caractéristiques de l’anisotropie induite, ainsi que les non-linéarités. En outre, l’anisotropie induite par la contrainte se produit pendant le processus de chargement sur les sols, par exemple, les charges ou les déplacements. Dans ce travail, un nouveau modèle qui est une combinaison de modèle hyperélastique Houlsby et modèle élastoplastique Plasol a été proposé. Ce nouveau modèle a pris en compte la réponse non linéaire de la contrainte dans le domaine élastique et plastique, et l’élasticité anisotrope a également été bien considérée. En outre, les problèmes de l’écoulement de la déformation plastique a été calibré par un algorithme d’intégration approprié. Plus tard, le nouveau modèle a été vérifié en utilisant la méthode numérique et comparé aux expériences de laboratoire dans des conditions triaxiales axisymmétriques. Les résultats de comparaison ont montré un bon effet de simulation du nouveau modèle qui a juste utilisé un seul ensemble de paramètres pour un sol spécifique dans différentes situations de contraintes. Ensuite, l’analyse de la nouvelle variable interne du modèle, c’est-à-dire l’exposant de pression, a montré que la valeur de l’exposant de pression qui correspond au degré d’anisotropie a eu un effet évident sur la réponse contrainte-déformation. De plus, ce type d’effet est également affecté par la densité et l’état de drainage des échantillons. En s’appuyant sur un nouveau modèle, un facteur de sécurité qui fait référence au critère de travail de deuxième ordre a été adopté et testé dans un modèle axisymétrique et un modèle de pente réel. Il a montré que la valeur négative ou la diminution spectaculaire du travail global normalisé de second ordre se produit lors d’une défaillance locale ou globale avec apparition d’énergie cinétique. Cette caractéristique du travail du second ordre peut également être affectée par l’exposant à pression variable. Enfin, un nouveau modèle a également été comparé à un modèle élastoplastique qui considère à la fois l’anisotropie élastique et la dilatation anisotrope, c’est-à-dire le modèle SANISAND modifié. Les avantages et les inconvénients ont été illustrés dans les résultats de comparaisonIn order to model the behavior of geometarials under complex loadings, several researches have done numerous experimental works and established relative constitutive models for decades. An important feature of granular materials is that the relationship between stress and strain especially in elastic domain is not linear, unlike the responses of typical metal or rubber. It has been also found that the stress-strain response of granular materials shows the characteristics of cross-anisotropy, as well as the non-linearities. Besides, the stress-induced anisotropy occurs expectedly during the process of disturbance on soils, for example, the loads or displacements. In this work, a new model which is a combination of Houlsby hyperelastic model and elastoplastic Plasol model was proposed. This new model took into account the non-linear response of stress and strain in both elastic and plastic domain, and the anisotropic elasticity was also well considered. Moreover, the overflow problem of plastic strain in plastic part was calibrated by a proper integration algorithm. Later, new model was verified by using numerical method and compared with laboratory experiments in axisymmetric triaxial conditions. The comparison results showed a good simulation effect of new model which just used one single set of parameters for a specific soil in different confining pressure situations. Then the analysis of new model internal variable, i.e., pressure exponent, illustrated that the value of pressure exponent which corresponds to the degree of anisotropy had an obvious effect on the stress-strain response. Moreover, this kind of effect is also affected by the density and drainage condition of samples. Basing on new model, a safety factor which refers to the second-order work criterion was adopted and tested in axisymmetric model and actual slope model. It showed that the negative value or dramatic decreasing of global normalized second-order work occurs accompanying with a local or global failure with a burst of kinetic energy. This feature of second-order work can also be affected by the variable pressure exponent. At last, new model was also compared with an elastoplastic model which considers both anisotropic elastic and anisotropic dilatancy, i.e., modified SANISAND model. Both advantages and disadvantages were illustrated in the comparison results
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Le, Thi Minh Hue. "Stochastic modelling of slopes and foundations on heterogeneous unsaturated soils." Thesis, University of Glasgow, 2012. http://theses.gla.ac.uk/3097/.
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Many geotechnical engineering structures, including embankments, slopes and foundations involve unsaturated soils, either because they are constructed of compacted fills which are unsaturated after placement or because they include a zone of unsaturated natural soils above the water table. Moreover, both compacted fills and natural soils are inherently heterogeneous, which leads to an important but complex class of problems whose analysis involves consideration of heterogeneous unsaturated soil. Both partial saturation and material heterogeneity significantly influence the overall behaviour of the soil domain and have been widely acknowledged as particularly important factors to be accounted for during geotechnical analysis. Research on these two areas has however evolved almost independently, leaving a gap in the understanding of problems relating to heterogeneous unsaturated soils. The aim of this thesis is to contribute to bridging this gap. Three boundary value problems, namely seepage through a flood defence embankment, stability of a slope and differential settlement (rotation) and bearing capacity of a rigid foundation, were investigated with reference to unsaturated soils which have spatially varying material properties. The finite element method was combined with random field theory to stochastically analyse each problem by employing unsaturated soil constitutive models covering both hydraulic and mechanical behaviour and randomly varying, but spatially correlated, soil properties. Stochastic modelling was undertaken by means of Monte Carlo simulations which involved a large number of finite element analyses, each with a different random property configuration. The collective responses were statistically characterised by their mean, standard deviation and probability distribution function, which provide a powerful probabilistic tool for risk and reliability assessment. The thesis demonstrates that the simultaneous existence of heterogeneity and partial saturation can significantly modify the soil response to a change of hydraulic boundary conditions (with respect to the homogeneous case or where the effects of partial saturation are neglected) and, in many cases, can exacerbate the risk of unsatisfactory performance of slopes and foundations. Notably, heterogeneity of soil porosity causes variability of both permeability and degree of saturation in unsaturated conditions, which can lead to a counter-intuitive tendency of water preferably following a path through low porosity regions, instead of high porosity regions as in the saturated case. This is because the influence of porosity on the degree of saturation at a given suction can counteract the influence of porosity on the intrinsic permeability. Moreover, if the influence of porosity on both intrinsic permeability and degree of saturation is taken into account, it is possible to obtain rather unexpected results such as for example the reduction of the mean and variation of steady state flow across randomly heterogeneous embankments compared with the case in which porosity only affects permeability. The thesis also shows that wetting events (e.g. rainfall) can cause, during transient state, a significant reduction in the stability of an unsaturated slope but can also lead to an increase in the range of variation of the factor of safety if the slope has spatially varying porosity. Consequently, the probability of failure of the slope tends to be significantly higher during transient state than at a final steady state when hydrostatic conditions have been reinstated. An important finding from the study of the heterogeneous unsaturated slope is that rainfall infiltration results not only in a decrease in factor of safety but also in a decrease in size of the sliding mass. Therefore, the risk assessment of a heterogeneous unsaturated slope taking into account both factor of safety and size of the sliding mass can lead to different conclusions compared to the conventional case when only the factor of safety is considered. The study of a rigid foundation resting on a heterogeneous unsaturated soil has found that the settlements induced by rainfall infiltration depend on the nature of the spatially varying material property. A rigid symmetrical foundation lying on soils with heterogeneous preconsolidation stress rotates (i.e. experiences differential settlement between the foundation ends) even though the wetting front migrates into the soil domain symmetrically about the centreline of the foundation. Conversely, the same foundation lying on soils with non-uniform porosity rotates because of the asymmetrical migration of the wetting front into the ground, which is caused by the variability of permeability and degree of saturation associated with porosity heterogeneity. Importantly, the thesis emphasizes that the rotation of the foundation cannot be detected if partial saturation and spatial variability are not simultaneously taken into account.
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Holcombe, Elizabeth Ann. "Modelling landslide risk on highway cut slopes in developing countries." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440028.
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