Dissertations / Theses on the topic 'Fractured Slope'

Landslides of the lateral spreading type, involving brittle geological units overlying ductile terrains, are a common occurrence in the sandstone and limestone plateaux of the northern Apennines of Italy. These instability phenomena can become particularly risky, when historical towns and cultural heritage sites built on the top of them are endangered. Neverthless, the mechanisms controlling the developing of related instabilities, i.e. toppling and rock falls, at the edges of rock plateaux are not fully understood yet. In addition, the groundwater flow path developing at the contact between the more permeable units, i.e. the jointed rock slab, and the relatively impermeable clay-rich units have not been already studied in details, even if they may play a role in this kind of instability processes, acting as eventual predisposing and/or triggering factors. Field survey, Terrestrial Laser Scanner and Close Range Photogrammetry techniques, laboratory tests on the involved materials, hydrogeological monitoring and modelling, displacements evaluation and stability analysis through continuum and discontinuum numerical codes have been performed on the San Leo case study, with the aim to bring further insights for the understanding and the assessment of the slope processes taking place in this geological context. The current research permitted to relate the aquifer behaviour of the rocky slab to slope instability processes. The aquifer hosted in the fractured slab leads to the development of perennial and ephemeral springs at the contact between the two units. The related piping erosion phenomena, together with slope processes in the clay-shales led to the progressive undermining of the slab. The cliff becomes progressively unstable due to undermining and undergoes large-scale landslides due to fall or topple.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO 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.

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 diminution
This 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

One of the most significant challenges of open-cut mining is to provide stability for the excavated slopes. Unrealistic predictions of the slopes’ behaviour during and after mining operations can lead to the failure of slopes, and this may pose a threat to human lives, the economy, and the environment. By excavating soft rock masses in open-cut mines, pre-existing joints can open and new joints can form behind excavated slopes. This phenomenon is due to the geotechnical character of the materials and stress relief movements of the excavated slopes. The stability of slopes in the rock masses is significantly influenced by the existence of discontinuities such as joints. The water flows in the opened joints can change the pore water pressure distribution in the slopes. The interaction between the joints and the water may impose different loading scenarios on the open-cut mines and put the safety of mining operations at risk. The analysis of slope stability can become more complicated because of the presence of water, discontinuities, and their interaction within the slopes in open-cut mines. This study investigates the hydromechanical interactions in the saturated jointed slopes due to pore water pressure changes. The second-largest open-cut mine in Australia, the Yallourn brown coal open-cut mine located in Victoria, was chosen as the case study for this research. In this study, several coupled pore fluid diffusion and stress-strain analyses are conducted using the extended finite element method (XFEM) in conjunction with the finite element method (FEM). This study firstly examines a joint aperture and pore water pressure changes of the excavated jointed slope due to installing a drainage system and backfilling in front of the slope. Secondly, a series of sensitivity analyses are carried out on the pore water pressure distribution changes to the variation of the permeability magnitude of the material and leakage properties of the joint surfaces. Finally, to control the pore water pressure of the saturated jointed slope, a series of drainage systems is designed. The arrangement and length of the drains are optimised by conducting a series of sensitivity analyses on the leakage properties of the joint and the permeability of the soft rock.
Doctor of Philosophy

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.

Submarine landslides, commonly triggered by earthquakes, significantly affect tsunami wave heights. Subaerial landslides can also generate tsunamis (if the land flows into a body of water) and may be catastrophic in nature, causing human casualties and direct property damage. This work focuses on landslides associated with shear band that develops beneath the slipping mass. Accordingly, we consider a landslide as a dynamic process when a shear band emerges along the potential failure surface. Within this band, the shear strength decreases due to the softening behaviour of the particulate material. Material above the band moves downwards, causing the band to propagate dynamically. This already produces a landslide velocity before the slide reaches the post-failure stage and begins separating from the substrata and generating tsunami. However, existing models of tsunamigenic landslides assume zero initial slide velocity. Previous analyses of the catastrophic shear band propagation in slopes of normally- and over-consolidated sediments have shown that a relatively short initial failure zone is sufficient to cause a full-scale landslide. For the shear band to propagate, the energy produced in the body by an incremental propagation of the shear band must exceed the energy required for the propagation. This consideration separates the shear band growth into progressive (stable) and catastrophic (dynamic) stages and treats the band growth as a true physical process rather than an instantaneously appearing discontinuity. This work considers a dynamic shear band problem formulated within the framework of the Palmer and Rice’s [1973] approach. We obtain the exact, closed-form solution for the shear band and landslide velocities as well as for the spatial and temporal distributions of strain and material velocity. This solution assesses when the slide fails due to the limiting condition near the propagating tip of the shear band. We also obtain a simple asymptotic solution, which is compared to the exact solution. In the case of submerged slopes, the obtained solutions are used in landslide and tsunami height analyses. Our results suggest that the conventional static approach to the slope stability analysis leads to a significant underestimation of the slide size (volume). In most cases, the volumes of catastrophic slides are roughly twice the volumes of progressive slides. For submerged slides, this dynamic effect further manifests itself in increasing the tsunami magnitude compared to the static case.

The use of remote techniques to capture the geometrical characteristics of rock masses has seen increased use and development in recent years. Apart from the obvious improved Health and Safety aspects, remote techniques allow rapid collection of digital data that can be subsequently analysed to provide input parameters for a variety of geomechanical applications. Remote data capture is a new technique used to collect geotechnical data and little independent work has been done concerning the comparative limitations and benefits of photogrammetry and laser scanning. Photogrammetry and laser scanning produce three dimensional digital representations of a studied rock face which can then be mapped for geotechnical data using specialist software. Research conducted at Camborne School of Mines, University of Exeter has focussed on developing robust and flexible methodologies for remote data capture techniques, namely photogrammetry and laser scanning. Geotechnical characterisation for photogrammetry was tested using the CSIRO Sirovision software and laser scanning was used with SplitFX from Split Engineering. A comparative method of assessing the error between orientation measurements was developed based on calculating the pole vector difference between remotely captured and traditionally hand-mapped data. This allowed for testing of the benefits of the remote data capture systems and limitations whilst comparing them with conventional hand-mapping. The thesis also describes the results of detailed comparisons between hand-mapping, photogrammetric and laser scanned data collection for discontinuity orientation, roughness, discontinuity trace lengths and potential end-use applications. During fieldwork in Cornwall, Brighton Cliffs and northern France it was found that remote data capture techniques struggled to collect orientation data from intensely fractured rock masses where features are primarily represented as discontinuity traces. It was found that both photogrammetry and laser scanning produce orientation data comparable to traditionally mapped data, with an average pole vector difference less than 12° from data mapped from the Tremough Campus road cutting to the University of Exeter’s Cornwall Campus. Set analysis on 151 comparable data points yielded a maximum set pole vector difference of 9.8°, where the closest difference was 2.24°. Testing the accuracy of discontinuity trace orientations captured by photogrammetry using the pole vector difference methods indicate that planar derived orientations are more accurate, with an average difference of 16.67° compared to 37.72°. This thesis contains the reviews and analyses of photogrammetry and laser scanning for use in characterising natural and manmade rock slopes. Improved field and post-processing methodologies have been developed to aid the safe, efficient and suitable geotechnical characterisation of rock fracture networks. The continual development and use of remote mapping techniques, whilst supplementing their unique qualities with traditional mapping, have the capability to revolutionise rock mass mapping. Particular development needed is the implementation of ISRM guidelines to standardise photogrammetric and laser scanning fieldwork and post-processing data analysis.

La mesure des déplacements de surface liés â l'activité volcanique est une méthode très utilisée dans la surveillance et l'étude des volcans actifs. De nombreux modèles mécaniques ont été réalisés pour tenter de déduire la structure interne de ces données de déplacements, et notamment pour localiser les chambres magmatiques. Mais ils négligent tous le caractère fortement hétérogène et discontinu des édifices volcaniques. Un nouveau modèle permettant précisément l'étude des milieux hétérogènes et fracturés est utilisé. Son hypothèse de base est que l'édifice se comporte comme s'il était constitué d'un assemblage de blocs se déplaçant les uns par rapport aux autres. L'éruption très bien documentée du Mont St Helens (1980) sert de test pour cette méthode de blocs, en permettant de comparer déplacements calculés et déplacements mesurés. Quatre modèles bi-dimensionnels de ce volcan sont construits à partir d'une coupe géologique nord-sud. Chacun d'eux permet de tester l'effet d'un paramètre du modèle (géométrie, conditions aux limites, coefficient de frottement entre blocs, chemin de sollicitation). L'intrusion d'un dôme de lave à l'intérieur du flanc nord est simulée par l'application d'une montée en pression incrémentale puis les modèles sont soumis à une accélération horizontale simulant un séisme. Les résultats de cette modélisation mettent en évidence la dépendance des modes de déformation et de rupture vis à vis du coefficient de frottement entre les blocs. On obtient un assez bon accord avec les observations pour la plus faible des deux valeurs de ce coefficient testées (O. S). La rupture du flanc nord en grand glissement de terrain se produit aussi bien sous la seule influence de la montée en pression que sous pression et séisme combinés. Mais le second type de chargement donne un meilleur accord des résultats avec la réalité, et confirme ainsi qu'un séisme était bien à l'origine de l'éruption. Enfin, on discute, à la lumière de ces résultats, de la possibilité d'appréhender les structures internes et les mouvements du magma, à partir des mesures de déplacements de surface

Le travail de recherche a pour objectif la realisation du logiciel degres destine a la prevision de la geometrie de la fosse d'une mine a ciel ouvert et la detection des risques de rupture. Il a ete mis en oeuvre sur le site de la "grande decouverte" de carmaux (tarn - france)

De récentes expérimentations réalisées sur des sites réels, ont permis de mettre en évidence la complexité du comportement de groupe de pieux dans une pente instable. On fait le point sur les méthodes existantes et on approfondit l'étude du mécanisme du comportement du sol au voisinage d'une rangée de pieux en se limitant au phénomène d'interaction sol-pieu. Apres étude bibliographique du phénomène donnant lieu à la programmation de deux des méthodes les plus significatives, on réalise deux approches en déformation: modélisation en continuum élastique permettant de prendre en compte une géométrie de maillage des pieux quelconques et d'appliquer au groupe une sollicitation en déplacement très générale, modélisation s'appuyant sur la méthode des éléments finis et sur un modèle bidimensionnel horizontal simulant l'écoulement du sol entre une rangée de pieux. Comparaison de diverses méthodes.

Rock slope stability is a particularly important topic in rock engineering. The circular failure of highly fractured rock slopes is a critical failure mode that can cause severe damage. Over the past decades, significant research has been devoted to soil slopes and failure modes of rock slopes controlled by discontinuities. However, there have been few attempts to systematically study the circular failure mode of rock slopes. Circular failure is controlled by the strength of the rock mass. While the strength of a rock mass is difficult to measure directly, the Hoek-Brown (HB) strength criterion has proved effective and convenient for its estimation. This research presents a systematic study of the stability of highly fractured rock slopes using the HB strength criterion. Both deterministic analyses and probabilistic analyses are included. The relationship between the input (GSI, mi, σci, and their variability) and the output, Factor of Safety (FS) and Probability of Failure (PF), is investigated. Slide6.0 and a limit equilibrium model programmed in Matlab are used for FS calculations; Monte Carlo simulations are applied for PF calculations. The deterministic analysis aims to characterise the sensitivity of FS to the changes in HB parameters (FS sensitivity). A sensitivity graph analysis and an equation fitting analysis are developed. The sensitivity graph analysis displays the relationship between HB parameters and FS directly. The equation fitting analysis fits a large amount of data generated by Slide6.0 with an equation connecting HB parameters and FS, and then determines FS sensitivity from the derivatives of this equation with respect to HB parameters. It is found that slopes with the same geometry and the same FS (but different combinations of HB parameters) can have quite different sensitivity and GSI is the most critical parameter in this respect. With the increase in GSI, FS becomes increasingly sensitive to the change in GSI and that in σci. The probabilistic analysis investigates the relationship between the variability of HB parameters (quantified by the coefficient of variation COV and scale of fluctuation θ) and PF. Its effectiveness in assessing the impact of FS sensitivity on slope stability is also studied. A series of parametric studies are implemented. It is found that there is a strong relationship between FS sensitivity and PF: for slope cases with identical FS and the same COV of input HB parameters, a slope of higher FS sensitivity has a higher PF, indicating a higher risk. The relative contributions of the variability of HB parameters to PF are also compared. It is found that when the COV of GSI, mi, and σci are identical, the variability of GSI makes the largest contribution; however, when these COV are set to their upper-limit values observed in engineering practice, the high variability of σci makes the largest contribution. Finally, the investigation demonstrates that spatial variability of HB parameters (applicable to mi and σci in this study) has significant influences on slope stability. For a slope with FS > 1, the PF increases as the scale of fluctuation θ of HB parameters increases. Also, larger θ makes the effect of FS sensitivity on slope stability more significant.
Thesis (M.Eng.Sc.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2013

碩士
國立成功大學
資源工程學系碩博士班
95
In this study, a formulation of the BEM, based on the relative displacements at the crack tip, is used to determine the mixed mode SIFs of isotropic and anisotropic rocks. The BEM formulation is such that the displacement integral equation is only collocated on outside boundary and the traction integral equation is only collocated on one side of the crack surface. A decoupling technique can be used to determine at the mixed mode SIFs of isotropic and anisotropic rocks based on the relative displacements at the crack tip. Numerical examples for the determination of the mixed mode SIFs for anisotropic rocks with different crack inclination angel, crack length, and degree of material anisotropy are presented. In this study presents a fracture propagation analysis for simulation the process of slope failure. The development of the simulating failure surface is subject to the fracture propagation and stress intensity factor under mixed mode constraints.

碩士
逢甲大學
土木工程學系
101
This dissertation is about identification of existing shear zone structures and displaced landforms in Cishan Creek Basin, and investigation of the cause of large-scale landslides in Xiaolin Village in Cishan Creek Basin and the impacts of landslide dam outburst on riverbank in Cishan Creek Basin. Based on the result of this study, the presences of ruptures with different strikes and the displaced landforms have been found in the river sections with severe disasters in Cishan Creek Basin. Affected by the localizations of deformations with brittle fractures, the large landslides often took place even when the rainfall was not that heavy. Therefore, the rainfall is not the critical factor of the instability of riverside slopes in Cishan Creek Basin. The large landslide at riverside slope usually leads to landslide dam. The outburst of landslide dam will result in huge amount of debris flow, and such shock and vibration will lead to the erosion and scouring of riverside slope with localized shear zone rocks with brittle fractures. Keywords: fractured zone, landslide, landslide dam, brittle fracture

碩士
國立成功大學
資源工程學系
104
Recent research has found that the maximum amplification direction of slope site response is oriented along local topographic features, and such directivity phenomena is caused by a combination of topographic, lithologic and geologic factors. The purpose of this study is to find the variation of the slope site response directivity which is dependent on the change of slope geologic condition by observing the spectrums of seismic coda wave which were recorded across the happen of changing event. The seismograph set on the slope at planned Shin-Wen Reservoir site, southeastern Taiwan is chosen for this research because there was a fracture zone occurred near the station during Typhoon Morakot at 2009. By rotating the pair of horizontal seismograms and calculating with HVSR and SSR methods to get the directivity of slope site response. According to the results of each seismic record, it shows that the azimuths of directivities are distributed along about N0°E. However, the distribution of azimuths after the fracture occurred is much scattered than before the occurrence of fracture. This research suggest that the phenomena may cause by the occurrence of the fracture which had changed the slope physical condition of geological material. This method might be able to detect the existence of subsurface fracture near the station.