The LMVD Method of Planes has been used for many years by the New Orleans District of the U.S. Army Corps of Engineers to analyze the stability of flood control structures in the New Orleans hurricane protections system. The Method of Planes assumes a three-part, noncircular slip surface and generally does not satisfy any form of static equilibrium. In computing a factor of safety, the Method of Planes considers a balance of horizontal “resisting” and “driving” forces in computing a factor of safety. To better understand how the results of slope stability analyses with the Method of Planes compare with results from more rigorous procedures capable of analyzing slip surfaces with different shapes, a parametric study was performed by analyzing twenty earthen levee cross sections believed to represent the various levee configurations in southeastern Louisiana. Analyses were performed with a force equilibrium procedure that assumed a horizontal inclination for the interslice forces and Spencer’s (1967) procedure, and the results were compared with the solutions from the Method of Planes. The force equilibrium procedure with horizontal side forces was selected because the procedure is believed to yield results that are similar to results from the Method of Planes, and Spencer’s procedure was utilized because it is the only procedure considered in this study to completely satisfy static equilibrium. The analyses performed with the force equilibrium and Spencer’s procedures included analyses for the critical slip surfaces from the Method of Planes as well as analyses for critical circular and noncircular slip surfaces. It was shown with the results of the analyses that the shape of the assumed slip surface has a great effect on the differences in the factors of safety from Spencer’s procedure and the Method of Planes. / text

In this research, extensive use has been made of limit equilibrium methods of analysis for studying the stability of slopes. For the determination of the factor of safety (FOS) of slopes, the usual two-step process has been adopted; (a) assuming a slip surface for the soil mass, and (b) using the appropriate limit equilibrium equation(s). Eight wellknown limit equilibrium methods have been programmed to calculate different FOS values. The comparative performance of the various analyses has been carried out successfully using case studies. The innovative use of Gauss quadrature to calculate the FOS values has been shown to reducet he iterative sequencesd ramatically with no loss of accuracy. A visco-plastic flow model has been proposed to estimate lateral forces on piles used for slope stabilisation. The present research data occupies an "in-between" position to the previously reported values, with the variation trend being confirmed satisfactorily in all cases. Slope stabilisation due to the presence of a row of piles has been investigated using two distinct lateral load estimations. These include theories of plastic deformation and the proposed visco-plastic flow which are modelled and implemented in a computer program. Eight well-known methods of slope stability analyses have been adopted and computer coded to re-calculate FOS values for a slope reinforced by a row of piles. A Finite Element computer program has been developed to evaluate the displacement, bending moment and shear force along the pile axis. The pile is analysed at two levels above and below the slip 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.

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

This thesis deals with the difference between two calculation programs for slope stability, namely Geoslope SLOPE/W and Novapoint GeoSuite Stability. The purpose of the thesis is to compare the two calculation programs with regard to the analysis of slope stability, as well as the two programs' handling of data. The two calculation programs use different Limit equilibrium methods to calculate safety factor and sliding surfaces for slopes. It can be expected that the result should be similar to one another, as well as the fact that both the calculation programs use different Limit equilibrium methods, but also when large differences in both safety factor and critical sliding surface give unreliable results. The thesis will also address the factors that may lie behind the fact that a possible stability failure should take place in a slope, as it gives an increased understanding of the analyzes that have been done. The work was carried out by modeling slopes with identical geometric relationships and identical material properties in the two calculation programs, a safety factor and a critical sliding surface for the slopes were developed for both programs and then compared with each other. / Föreliggande examensarbete behandlar skillnaden mellan två beräkningsprogram när det kommer till släntstabilitet, nämligen Geoslope SLOPE/W och Novapoint GeoSuite Stability. Syftet med examensarbetet är att jämföra de båda beräkningsprogrammen avseende vid undersökning av släntstabilitet, samt de två programmens hantering av data. De två beräkningsprogrammen använder sig av liknande Limit equilibrium-metoder för att beräkna säkerhetsfaktor samt glidytor för slänter. Man kan förvänta sig att resultatet bör vara varandra likt då dels att de både beräkningsprogrammen använder sig av liknande Limit equilibrium-metoder, men också då stora skillnader i både säkerhetsfaktor och kritisk glidyta ger opålitligt resultat. Examensarbetet kommer även ta upp de faktorer som kan ligga bakom att ett eventuellt brott ska ske i en slänt, då det ger ökad förståelse för de analyser som gjorts. Arbetet utfördes genom att slänter med identiska geometriska relationer samt identiska materialegenskaper modellerades i de båda beräkningsprogrammen, en säkerhetsfaktor samt kritisk glidyta för slänterna togs fram för båda programmen och jämfördes sedan med varandra.

Análises de estabilidade de taludes, em mineração, são uma das atividades mais importantes do processo de obtenção de um bem mineral. Assegurar a estabilidade das escavações e a segurança do empreendimento são vitais para o processo de extração e, para tanto, a escolha da forma de análise (2D, quasi-tridimensional ou 3D) ou do método (equilíbrio limite ou análise numérica) mais propício para esse tipo de estudo é de suma importância. Muitas vezes o engenheiro responsável acaba baseando sua escolha na familiaridade com determinada metodologia ou na praticidade de determinado programa, em detrimento a fatores técnicos e de relevância para o estudo. Dessa forma, visando preencher tal lacuna existente atualmente e facilitar a escolha da melhor metodologia a ser utilizada, o presente estudo reúne os principais métodos conhecidos, suas vantagens e desvantagens e, assim, propõem uma metodologia para que essa escolha seja baseada em parâmetros técnicos relevantes. A metodologia proposta é, de certa forma, restritiva na escolha dos procedimentos que serão considerados, uma vez que, buscou-se utilizar métodos que tenham sua aplicabilidade comprovada, que possuam vantagens consideráveis sobre outros métodos e que sejam rigorosos, ou seja, satisfaçam todas as condições de equilíbrio (forças e momentos). Para corroborar com a metodologia proposta, quatro situações práticas diferentes foram apresentadas, demonstrando a aplicabilidade da metodologia. / Analysis of slope stability in mining is one of the most important activities of the process of obtaining a mineral resources. Ensuring the excavation stability and the safety of the project are vital to the extraction process. The choice of the form of analysis (2D, quasi-threedimensional or 3D) or of the method (limit equilibrium or numerical analysis) more suitable for this type of study is of paramount importance since, the responsible engineer often end up basing the analysis on familiarity with a particular methodology or on the availability of a particular program, to the detriment of technical factors and relevance to the study. Thus, in order to fill this existing gap and facilitate the selection of the best methodology to be used, the present study brings together the main known methods, their advantages and disadvantages and, therefore, presents a methodology for such a choice to be based on relevant technical parameters. The proposed methodology is somewhat restrictive in the choice of procedures that will be considered, since it has been tried to use methods that have proven applicability, that have considerable advantages over other methods and that are rigorous, satisfying all equilibrium conditions (forces and moments). In order to corroborate the proposed methodology, four different practical situations were presented, demonstrating the applicability of the methodology.

A pesquisa voltada para a retroanálise de taludes de mineração está se tornando cada vez mais importante. As dimensões das atuais cavas de mineração visam sempre obter a melhor relação entre custo, benefício e segurança. Isso exige que por vezes o trabalho ocorra próximo destes limites. Neste trabalho o estudo de retroanálise consiste em um talude misto composto por aluvião e rocha em uma mineração de carvão localizada no município de Arroio dos Ratos, RS. O objetivo foi realizar um estudo de retroanálise onde se utilizou dois métodos de análise método dos Elementos Finitos (MEF) e o método do Equilíbrio Limite (EL). A metodologia adotada foi dividida em três fases: uma etapa de campo, para coleta do material e dados geométricos do talude, uma etapa de laboratório para caracterizar todo o material e a última etapa computacional onde foram gerados os modelos e simulações numéricas através dos softwares comerciais da empresa RocScience, sendo eles o SLIDE e o RS2. Os resultados encontrados mostraram que a porção do talude composta por aluvião apresentava seis camadas intercaladas de areias bem graduadas e argilas de média a alta plasticidade. Em relação as simulações, observou uma diferença entre o MEF e EL devido ao grande número de camadas presentes no talude e a interação entre elas. Foram criados quatro diferentes cenários para observar o comportamento do talude, com presença e ausência de água. O MEF mostrou uma superfície de ruptura próxima a encontrada porem com a presença de água o Fator de Segurança (FS) sofreu uma grande depreciação. O EL considerou uma superfície de ruptura satisfatória, nas simulações com presença de água FS sofreu uma depreciação mínima mesmo com máxima saturação de água no talude. Apesar das diferenças ambos os métodos são confiáveis mas devem ser usados de forma adequado ao tipo de problema existente. Situações mais simples e com taludes mais homogêneos o EL trona-se mais indicado, para problemas de maior complexidades e interações entre camadas o MEF se mostrou satisfatório e com boa resposta. O resultados através do MEF se aproximaram mais da situação real encontrada em campo. / A research focus on retro analysis on mine slopes is becoming increasingly important. The dimensions of current mining caves aim to always obtain the best cost benefit ratio as well as the highest safety level. This demands that the work sometimes is done within these limits. In this paper the study of retro analysis is made up of a mixed slope composed of alluvial and rocks, in a coal mine in Arroio dos Ratos, RS. The goal was to carry out a retro analysis study using two analysis methods: The Finite Element Method (FEM) and Limit Equilibrium analysis (LE). The methodology adopted was split into three phases: a field stage for the sample collection and slopes geometric , a laboratory stage to classify all the material and a final computacional stage were model and numerical simulations were created by way of commercial software, Slide and RS2, by RocScience. The results showed that the portion of the slope composed of alluvium had six layers interspersed with well graded sands and high plasticity clays. The simulations observed a difference between the FEM and LE due to the number of layers present in the slope and the interaction among them. Four different scenarios were created in order to observe the behavior of the slope. The FEM presents surface failure similar to one found in the field. The LE always takes into consideration the overall critical surface which is not observed in the field, it also show high security factor levels above one 1.3 that does not reflect a real situation since the slope is collapsed. In spike of the differences, both methods are reliable but they must be used according to the existing problems. For simpler situations with homogeneous slopes LE is recommended while move complex problems and interactions among lawyers calls for FEM.

[Truncated abstract] The feasibility of using interlocked light gauge sheet piles to form a deep cross-sectional wall embedded in a residual slope or with a berm support is explored. This thesis compares the performance of a large section modulus sheet pile wall as an alternative to a concrete diaphragm wall, acting as an embedded cantilever wall on a slope (ECWS) by means of experimental centrifuge tests, numerical models and analytical methods. Abaqus (Hibbitt, Karlsson and Sorensen Inc, 1997) was used to conduct extensive numerical trials on the structural performance of the sheet pile wall model prior to the actual physical testing. The Abaqus results showed that the integrity of the interlock and reduced modulus action (RMA) due to slippage along the interlocked joint did not cause premature buckling of the thin wall even at the ultimate load. Further, a comparative study using centrifuge tests on 1:30 scaled models and Plaxis analysis demonstrated that under the worst condition with high water table, the rigid sheet pile wall of 1.32 m cross-sectional width carried a higher ultimate surcharge load with a much lower top of wall deflection, compared to a more flexible 0.6 m thick cracked concrete diaphragm wall. The analysis of the wall/soil/slope interactions for an ECWS involves many inter-dependent variables in addition to the complications of considering an adjacent slope or a berm support. It is difficult for existing analytical approaches to take all these factors into account, and some form of numerical analysis, calibrated through field data and results from centrifuge model tests is necessary. From the observations of the centrifuge tests and finite element analysis, major assumptions about the failure of a stiff ECWS in a rotational mode were deduced and adopted in the proposed limiting equilibrium method (Leq). The plane strain Leq ECWS Abstract ii analysis is based on the framework of minimum upper bound limiting equilibrium with planar failure planes and a Mohr-Coulomb soil model. As compared to the traditional limit equilibrium analysis, the Leq method is a fully coupled analysis using the shear strength reduction technique (SSR). New formulations are proposed for the development of horizontal active and passive pressure distributions based on the experimental and FE models. The proposed active pressure profile used is derived by combining the Coulomb and Krey method, and empirically back-figured to curve-fit the centrifuge tests by Morris (2005). The proposed passive pressure profile of a rigid rotational wall in failure is adjusted to allow for an adjacent slope or berm support through a presumed elasto-plastic deformation instead of a linear rigid translation of the passive wedge. ... A parametric study was later undertaken using the Leq method to develop a series of non-dimensionalised graphs to study and draw summarised conclusions on the behaviour of the ECWS. The final conclusions on the comparative study of the centrifuge tests, Plaxis and Leq analyses demonstrated that the alternative light gauge steel sheet pile performed very well as an ECWS. A key factor in the performance of the sheet pile wall was attributed to the large 1.32 m cross-sectional width of the interlocked sections. This provided high bending stiffness and high moment stability from shear stresses acting on the back and front faces of the wall.

The cut slopes at a segment between Km 25+600 and 26+000 of the Antalya-Burdur Breakaway-Korkuteli State Road to be newly constructed have slope instability problems due to the existence of highly jointed limestone. The purpose of this study is to investigate the engineering geological properties of the units exposed at three cut slopes, to assess stability of the cut slopes, and to recommend remedial measures for the problematic sections. In this respect, both field and laboratory studies have been carried out. The limestone exposed at the cut slopes are beige to gray, fine grained, fossiliferous, and highly jointed. It has two joint sets and a bedding plane as main discontinuities. The kinematic analysis indicates that planar failure is expected at Km: 25+900. Limit equilibrium analysis show that the cut slopes with bench have no slope instability problems except rockfalls which endanger the traffic safety. In this thesis it is recommended to covering the cut slope with wire mesh and fibre reinforced shotcrete