To date, research has not focused on the behavior of concrete block stoppings subjected to excessive vertical loading due to roof to floor convergence. For this reason, the failure mechanism of stoppings under vertical loading has not been fully understood. Numerical models were used in combination with physical testing to study the failure mechanisms of concrete block stoppings. Initially, the behavior of a single standard CMU block was observed and simulated using FLAC. Full-scale stoppings were then tested in the Mine Roof Simulator and modeled using UDEC. Through a combination of physical testing and numerical modeling a failure mechanism for concrete block stoppings was established. This failure mechanism consists of development of stress concentrations where a height difference as small as 1/32â exists between adjacent blocks. These stress concentrations lead to tensile cracking and, ultimately, premature failure of the wall. / Master of Science

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.

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.

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. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

Mit dem zweidimensionalen numerischen Diskrete-Elemente-Programm UDEC wurde nach vorheriger Kalibrierung das Einstanzen einer keilförmigen Schneide in Gesteinsmaterial simuliert und mit Laborversuchen verglichen. Außerdem wurde ein Schneidprozess simuliert. Mittels einer selbst entwickelten Routine, welche die Gesteinselemente bei Überlastung zerteilt und ein ‚Re-meshing‘ erzeugt, konnten befriedigende Simulationsergebnisse erzielt werden. Mit der dreidimensionalen Simulationssoftware PFC3D auf Partikelbasis wurden Modelle mit Hilfe von Zug-, Druck-, Scher- und Stanzversuchen kalibriert und anschließend Schneid- und Bohrversuche simuliert. Die Schneidsimulationen erbrachten bezüglich der Kräfte bei verschiedenen Prozessparametern gute Übereinstimmung mit den Laborversuchen. Bei der Bohrsimulationen konnten Kräfte und Momente aus den Laborversuchen nur teilweise reproduziert werden.

Mit dem zweidimensionalen numerischen Diskrete-Elemente-Programm UDEC wurde nach vorheriger Kalibrierung das Einstanzen einer keilförmigen Schneide in Gesteinsmaterial simuliert und mit Laborversuchen verglichen. Außerdem wurde ein Schneidprozess simuliert. Mittels einer selbst entwickelten Routine, welche die Gesteinselemente bei Überlastung zerteilt und ein ‚Re-meshing‘ erzeugt, konnten befriedigende Simulationsergebnisse erzielt werden. Mit der dreidimensionalen Simulationssoftware PFC3D auf Partikelbasis wurden Modelle mit Hilfe von Zug-, Druck-, Scher- und Stanzversuchen kalibriert und anschließend Schneid- und Bohrversuche simuliert. Die Schneidsimulationen erbrachten bezüglich der Kräfte bei verschiedenen Prozessparametern gute Übereinstimmung mit den Laborversuchen. Bei der Bohrsimulationen konnten Kräfte und Momente aus den Laborversuchen nur teilweise reproduziert werden.:1 Einleitung.................................................................................................... 1 2 Grundlagen der Gesteinszerstörung .......................................................... 3 2.1 Die mechanische Gesteinszerstörung beeinflussende Faktoren................ 3 2.2 Bohrwerkzeuge .......................................................................................... 8 2.2.1 Anforderungen an Bohrwerkzeuge ...................................................... 8 2.2.2 Rollenbohrwerkzeuge .......................................................................... 9 2.2.3 Diamantbohrwerkzeuge....................................................................... 9 2.2.4 Hartmetallwerkzeuge ......................................................................... 11 2.2.5 Auswahl und Einsatz des Bohrmeißels.............................................. 12 2.3 Gestaltung des Bohrprozesses ................................................................ 13 2.4 Vergleich zwischen schneidender, drückender und schlagender Gesteinszerstörung .................................................................................. 14 2.5 Schneidende Gesteinszerstörung ............................................................ 15 2.5.1 Zerspankraft und deren Komponenten: ............................................. 15 2.5.2 Steinbearbeitung mit geometrisch unbestimmter Schneide............... 17 2.5.3 Steinbearbeitung mit geometrisch bestimmter Schneide................... 18 2.6 Drückende Gesteinszerstörung ................................................................ 27 2.7 Verschleiß ................................................................................................ 28 3 Stand der Technik .................................................................................... 31 3.1 Rollenmeißel ............................................................................................ 31 3.1.1 Experimentelle Untersuchungen........................................................ 31 3.1.2 Simulation der Rollenmeißel.............................................................. 34 3.2 Simulation von mechanischen Zerkleinerungsprozessen......................... 40 4 Zweidimensionale Simulation der Gesteinszerstörung mit UDEC ............ 71 4.1 Vorstellung UDEC .................................................................................... 71 4.2 Simulation eines Stanzversuchs mit Diskenmeißeln ................................ 73 4.2.1 Modellaufbau, Methodik..................................................................... 73 4.2.2 Kalibrierung des Gesteinsmodells ..................................................... 73 4.2.3 Simulation der Stanzversuche ........................................................... 74 4.3 Simulation von Schneidversuchen ........................................................... 83 4.3.1 Kalibrierung des Gesteinsmodells ..................................................... 83 4.3.2 Simulation der Schneidversuche ....................................................... 85 5 Dreidimensionale Simulation der Gesteinszerstörung mit PFC3D ............. 97 5.1 Vorstellung PFC3D .................................................................................... 97 5.2 Methodik der Parameterkalibrierung......................................................... 98 5.3 Kalibrierung an Postaer Sandstein ......................................................... 100 5.3.1 Verwendete Rechenmodelle............................................................ 100 5.3.2 Kalibrierung an einaxialen Duck- und Zugversuchen....................... 102 5.3.3 Kalibrierung an Scherversuchen...................................................... 113 5.3.4 Kalibrierung an Stanzversuchen...................................................... 120 5.3.5 Schlussfolgerungen aus der Kalibrierung ........................................ 124 5.4 Simulation von Schneidversuchen ......................................................... 124 5.4.1 Laborversuche................................................................................. 124 5.4.2 Simulationen mit fünffachem Partikeldurchmesser.......................... 128 5.4.3 Simulation mit der Originalkorngröße .............................................. 133 5.4.4 Zusammenfassung .......................................................................... 149 5.5 Simulation der Bohrversuche ................................................................. 149 5.5.1 Versuchsstand................................................................................. 149 5.5.2 Berechnung von Kräften und Momenten ......................................... 151 II 5.5.3 Vergleich verschiedener Rechenmodelle ........................................ 152 5.5.4 Vergleich der Simulation des Bohrversuches mit dem Schneidversuch.............................................................................. 163 5.5.5 Betrachtungen zu den einzelnen Schneidplatten............................. 165 5.5.6 Zusammenfassung .......................................................................... 168 6 Zusammenfassung..................................................................................169 6.1 Hauptbeiträge......................................................................................... 171 7 Extended Summary.................................................................................173 7.1 Two-dimensional simulation of the rock destruction with UDEC............. 173 7.1.1 Introduction...................................................................................... 173 7.1.2 Simulation of a stamping experiment with disc cutters .................... 173 7.1.3 Simulation of rock cutting experiments ............................................ 174 7.2 Three dimensional simulation of the rock destruction with PFC3D .......... 177 7.2.1 Introduction...................................................................................... 177 7.2.2 Calibration ....................................................................................... 177 7.2.3 Simulation of cutting experiments.................................................... 178 7.2.4 Simulation of drilling experiments .................................................... 182 8 Literatur ...................................................................................................187

This thesis presents the analysis of complex slope deformations through the application of numerical modelling techniques. Complex slope deformations, in this thesis, include cases where the use of more conventional analytical tools such as limit equilibrium techniques or the use of empirical criteria are not readily applicable. Such a scenario often results from adverse geological and environmental conditions or from human activity. Examples of complex slope deformations are the influence of underground mining on a slope, or situations where rigid jointed rocks overly relatively weak layers. The use of numerical modelling techniques, both continuum and discontinuum, in the analysis of slope stability problems has increased rapidly in the last decade and proved valuable in the analysis of complex geomechanical problems. Two numerical modeling programs FLAC (Fast Lagrangian Analysis of Continua) and UDEC (Universal Distinct Element Code) were used in this thesis. Three main groups of problems were investigated: (1) The analysis of deformation associated with rigid jointed rocks overlying relatively weak layers including a case study involving deformation taking place in the foundation of the Spis Castle in Slovakia. It was demonstrated that the type of deformation in such cases depends on the strength, deformability and thickness of the weak layer as well as the jointing pattern of the overlying rocks. It was shown, that the deformations at Spis castle are governed primarily by the presence of a weak, plastic "creep zone" under the base of the travertine blocks on which the castle is founded. (2) The analysis of toppling deformation in a weak rock slope comprising several lithostratigraphic units at the Luscar Mine, Alberta. It was found that the instability mechanism in the initial phase was flexural toppling, confined to a distinct quasi-linear failure surface which provided the shear plane for subsequent sliding movement. A prediction of slope stability for a planned mine extension in the same pit was made, thereby determining "safe excavation limits". (3) The analysis of interaction between underground mining and slope instability. The analyses of various slope deformation mechanisms that can be induced by underground mining are presented. The analysis of the Frank Slide in southwestern Alberta illustrated the critical role of underground mining at the base of the Turtle Mountain on triggering the final slope failure. The analyses present within this thesis demonstrate the application of numerical modelling techniques in the characterization of complex slope deformations. New interpretations of existing failure mechanisms were presented in the case of the Frank Slide, and improved understanding of the failure mechanism and slope deformation were gained in the Luscar Mine and Spis Castle case studies. Furthermore, hypothetical modelling studies relevant to underground mining and block-type deformations allow an increased understanding of complex slope deformations.

A l'opposé du dimensionnement de fondations d'ouvrages sur les sols, régi par des règles de calcul validées, le dimensionnement de fondations au rocher est mal maîtrisé. Jusqu'à présent, ceci n'a pas posé de problème majeur, car le dimensionnement de fondations se trouvait plutôt limité par la résistance du béton que par celle du massif rocheux. Mais la construction d'ouvrages d'art de plus en plus majestueux nécessite aujourd'hui une meilleure connaissance de ce domaine de la mécanique des roches. La première partie recense les méthodes les mieux adaptées pour déterminer la déformabilité et la résistance d'un massif rocheux. Elle présente les différentes méthodes de dimensionnement de fondations superficielle et semi-profonde au rocher. Enfin, elle analyse les textes réglementaires français et étrangers. Il existe peu de méthodes de dimensionnement de fondations qui tiennent compte du caractère discontinu des massifs rocheux ; le cas de fondations soumises à des efforts latéraux et à des moments renversants n'est quasiment pas traité. La deuxième partie consiste en l'analyse numérique du comportement de fondations superficielle et semi-profonde sur massif rocheux à l'aide du code de calcul par éléments distincts UDEC. Les résultats montrent que les discontinuités du massif rocheux ont un rôle primordial sur le comportement sous effort incliné de fondations semi-profondes. Selon leur pendage, les discontinuités peuvent diminuer considérablement la charge limite admissible. Quelques modèles analytiques simples à peu de blocs sont ensuite proposés, afin d'estimer - pour un dimensionnement préliminaire - la charge limite de rupture d'un puits marocain sous effort latéral. Les résultats numériques obtenus sont bidimensionnels; les résultats tridimensionnels peuvent être estimés à l'aide de coefficients de transfert 2D/3D, qu'il serait intéressant de vérifier à l'aide d'un code de calcul par éléments distincts tridimensionnel. Enfin, il serait nécessaire de valider les résultats de modélisation numérique sur un site réel.

No description available.