nÃo hà / A evoluÃÃo das anÃlises de estabilidade de taludes na Engenharia GeotÃcnica segue de perto o desenvolvimento da MecÃnica dos Solos. Escorregamentos de taludes sÃo uma das formas mais frequentes de movimento de massa. No caso de barragens de terra, trÃs dificuldades sÃo encontradas quando se analisa a estabilidade de taludes: a) a variabilidade dos parÃmetros de resistÃncia do solo; b) dificuldades de se prever as condiÃÃes de fluxo de Ãgua e as pressÃes piezomÃtricas resultantes, e c) dificuldade de antecipaÃÃo das formas mais provÃveis de ruptura, as superfÃcies potenciais a elas associadas e os mecanismos de ruptura envolvidos. Essas dificuldades refletem diretamente no nÃmero de falhas em barragens de terra, que responde por 66% dos acidentes em barragens em todo o mundo. Dados da AgÃncia Nacional de Ãguas apontam que entre 2002 e 2010 foram registrados 800 incidentes com barragens. Como acidentes de grandes proporÃÃes, cita-se a ruptura da barragem de rejeitos de Cataguazes (MG), em marÃo de 2003, que deixou milhÃes de pessoas por semanas sem abastecimento, em razÃo do lanÃamento de soda cÃustica no rio ParaÃba do Sul, bem como o rompimento da barragem de AlgodÃes, em maio de 2009, no PiauÃ. Dessa forma, em razÃo das inÃmeras incertezas nos projetos das barragens, à necessÃria a utilizaÃÃo de metodologia que leve em consideraÃÃo a variabilidade dos componentes envolvidos nas anÃlises de estabilidade de taludes, uma vez que essas incertezas nÃo sÃo consideradas nos mÃtodos determinÃsticos. A anÃlise probabilÃstica de estabilidade de taludes, utilizando o mÃtodo de Monte Carlo, torna-se uma importante ferramenta durante a construÃÃo, enchimento e operaÃÃo de barragens de terra. PropÃe este trabalho uma metodologia simplificada para estimar os parÃmetros hidrÃulicos do solo mediante a retroanÃlise das condiÃÃes de fluxo, comparando as cargas piezomÃtricas medidas no maciÃo, com as calculadas por um programa de computaÃÃo comercial, para, em seguida, estimar a probabilidade de falha nos taludes da barragem de terra. A probabilidade de falha do talude de jusante, anÃlise na condiÃÃo de cheia mÃxima e anÃlise de estabilidade do talude de montante na condiÃÃo de rebaixamento rÃpido, foram realizadas para o caso da barragem Olho dâÃgua, no Estado do CearÃ. / The evolution of slope stability analysis in geotechnical engineering has followed closely the development of soil mechanics . Slope landslides are one of the most frequent forms of mass movement . In the case of earth dams, three difficulties are encountered when analyzing the slope stability: a) the variability of soil strength parameters, b) difficulty of predicting the conditions of water flow and resulting piezometric pressures, and c) difficulty in predicting the most probable forms of rupture, the potential surfaces associated to them, and the rupture mechanisms involved . These difficulties reflect directly on the number of failures recorded with dams, which accounts for 66 % of accidents in dams around the world. Data from the National Water Agency of Brazil show that between 2002 and 2010, 800 incidents were recorded dams. As major accidents, the rupture of tailings in Cataguazes dam in the state of Minas Gerais in March 2003, which left millions of people without water for weeks , due to leakage of caustic soda in the ParaÃba do Sul river , as well as the failure in the AlgodÃo Dam, in May 2009, in Piauà state in northeastern Brazil may be mentioned . Thus, because of the many uncertainties in the projects of dams, the use of a methodology that takes into account the variability of the components involved in the analysis of slope stability of dams is necessary, since these uncertainties are not considered in deterministic methods. The probabilistic analysis of slope stability using the Monte Carlo method, turns out to be an important evaluating tool during construction, filling and operation of earth dams. This work proposes a simplified methodology for estimating soil hydraulic parameters, by means of back-analysis of seepage conditions, comparing the pressure heads measured by standpipe piezometer in the dam, together with those calculated by commercial computing program to, then, estimate the dam slopes probability of failures. The reliability analysis of the downstream slope of the dam in the high level of water condition was done, such as the backslope stability analysis during rapid drawdown of the Olho dâÃgua dam in the State of CearÃ, Brazil.

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

High incidences of slope movement are observed throughout Cuyahoga River watershed in northeast Ohio, USA. The major type of slope failure involves rotational movement in steep stream walls where erosion of the banks creates over-steepened slopes. The occurrence of landslides in the area depends on a complex interaction of natural as well as human induced factors, including: rock and soil strength, slope geometry, permeability, precipitation, presence of old landslides, proximity to streams and flood-prone areas, land use patterns, excavation of lower slopes and/or increasing the load on upper slopes, alteration of surface and subsurface drainage. These factors were used to evaluate the landslide-induced hazard in Cuyahoga River watershed using logistic regression analysis, and a landslide susceptibility map was produced in ArcGIS. The map classified land into four categories of landslide susceptibility: low, moderate, high, and very high. The susceptibility map was validated using known landslide locations within the watershed area. The landslide susceptibility map produced by the logistic regression model can be efficiently used to monitor potential landslide-related problems, and, in turn, can help to reduce hazards associated with landslides.

The geometric alteration of slopes is a reality that can be observed in several districts of the Peruvian capital. The construction of houses, roads, and other infrastructure can produce some slope instability and cause tragic events. Thus, a stability analysis was carried out for a slope located in the San Juan de Lurigancho district, specifically in the Virgen de Fátima sector. Therefore, for the present investigation, two models were made with the help of Phase2 software to identify the resistance reduction factors (SFR), which is a finite element-based program. To start the analysis, possible failures were identified, demonstrating that the slope does not present any possibility of failure. For the first model, we worked with a dip of 30° and identified an SFR = 19.26 for static conditions and an SFR = 9.66 for pseudo-static conditions. For the second model, we worked with a dip of 55°, this change in slope geometry shows a possible wedge failure, according to the kinematic analysis. Also, an SFR = 0.89 was identified for static conditions and an SFR = 0.48 for pseudo-static conditions. The results show very considerable changes and are due to the geometry of the slope, the presence of discontinuities, and the participation of seismic forces.

Deterministic methods have been used in geotechnical engineering for a long period, such as slope stability calculations. However, only applying deterministic methods is subjective and imperfect. There is a demand to develop a systematic methodology to link the assessed slope stability and field measurement data, which is also known as inverse analysis and forward calculation. Based on the Nya Slussen project, this thesis includes the development of a methodology, deterministic calculation for 4 cross sections using finite element program Plaxis 2D and probabilistic calculation for one section. Deterministic analyses showed satisfying results for all the studied cross sections since their factors of safety exceeded the minimum requirement. In probabilistic design, three parameters were found to have the most uncertainties through sensitivity analysis (undrained shear strength of clay, Young’s modulus of clay and friction angle of fill). Inverse analysis was done by testing different values of them in Plaxis and to try to match the displacement components provided by field measurement. After finding the best optimization for all the parameters, forward calculation gave a final factor of safety. It is suggested that both of the methods should be utilized together for better assessment.

The solid portion of waste disposal, known as Municipal Solid Waste (MSW) can be landfilled. Landfilling has proved to be a safe, sanitary and economical method of disposal. A by-product from wastewater treatment plants called biosolids is sometimes co-disposed along with MSW in landfills. Recent work at the University of Central Florida has focused on the behavior of the mixture of MSW and biosolids. As an increased amount of waste accumulates in these landfills, it creates a new problem – the geotechnical stability of landfills. In current literature, classical geotechnical testing methods have been followed to find the strength properties of these landfill materials. Furthermore, geotechnical methods of slope stability analyses have been employed to determine the stability of landfill slopes. As these materials have a high organic content, their strength properties may potentially change with time because of the decay of the organic materials. In the present work, an attempt is made to monitor the change in the geotechnical strength properties of the landfill materials as a function of time. Direct shear tests used for soil testing, with some modifications, were performed on cured compost samples of MSW mixed with biosolids. Geotechnical strength properties of these cured samples were compared to those of an artificially prepared mixture of MSW and biosolids, from the published literature. In addition, direct shear tests are also performed to find the interface properties of a geonet with the cured samples to check the role of a geonet in reinforcing the landfill slopes. A slope stability analysis software SLOPE/W is used to analyze the stability of the landfills. Cohesion is observed to decrease with time while the friction angle increases with time. Stability (the factor of safety against failure) of landfill slopes increases with time due to increased effective stresses and increased friction angle, as the organic material decays. This may result in additional subsidence but an increase in the effective shear strength with time. Based on the interface test results and subsequent slope stability analyses, it is found that the inclusion of a geonet improves the slope stability of a landfill. This could be a potential benefit to the landfill as reinforcement if properly placed. Based on the slope stability analysis on landfills with different slopes, it is concluded that the slope stability of a landfill is improved by keeping the slopes less steep.

When a clay soil is sheared, clay particles along the shear plane become aligned in the direction of shear, forming "slickensided" surfaces. Slickensided surfaces are often observed along the sliding plane in field landslides. Because the clay particles along a slickensided surface are already aligned in the direction of shear, the available shear resistance is significantly less than that of the surrounding soil. During an earthquake, ground shaking often causes landslide movement. For existing landslides or repaired landslides that contain slickensided rupture surfaces, it is reasonable to expect that the movement will occur along the existing slickensided surfaces, because they are weaker than the surrounding soil. The amount of movement that occurs is controlled by the dynamic resistance that can be mobilized along the slickensided surfaces. The objective of this study was to investigate, through laboratory strength tests and centrifuge model tests, the shearing resistance that can be mobilized on slickensided rupture surfaces in clay slopes during earthquakes. A method was developed for preparing slickensided rupture surfaces in the laboratory, and a series of ring shear tests, direct shear tests, and triaxial tests was conducted to study the static and cyclic shear resistance of slickensided surfaces. Two dynamic centrifuge tests were also performed to study the dynamic shear behavior of slickensided clay slopes. Newmark's method was used to back-calculate cyclic strengths from the centrifuge data. Test results show that the cyclic shear resistance that can be mobilized along slickensided surfaces is higher than the drained shear resistance that is applicable for static loading conditions. These results, coupled with a review of existing literature, provide justification for using cyclic strengths that are at least 20% larger than the drained residual shear strength for analyses of seismic stability of slickensided clay slopes. This represents a departure from the current state of practice, which is to use the drained residual shear strength as a "first-order approximation of the residual strength friction angle under undrained and rapid loading conditions" (Blake et al., 2002). / Ph. D.

This Thesis describes a method for determining and analysing the deformations in peat caused by a driven rigid wheel. Markers were placed in the peat sample and radiographs were taken as the wheel travelled over the surface of the peat. An analysis of the data revealed that a unique relationship existed between the positions of the markers and the positions of the wheel. The paths of the principal stress trajectories were determined by a graphical method; from the principal stress trajectories, it was possible to find the surfaces of maximum shear. The purpose of determining these surfaces is to allow the equilibrium of the soil mass to be investigated by the present theories in soil mechanics; it is to draw an analogy to the analysis of slope stability problems. / Thesis / Master of Engineering (ME)

Earthen levees are crucial components of a nation's flood protection system. However, in some regions, these levees face the unique challenge of being subjected to both floods and earthquakes throughout their lifespan, an aspect that is relatively unexplored in the existing literature. The primary aim of this research is to examine earthquakes' and floods' effects on earthen levee failures. Using numerical simulations, the seepage, slope stability, and liquefaction potential of an earthen levee were modeled by considering compound of different floods and earthquakes scenarios. Elkhorn Levee in Sacramento, CA, was used as a representative case study for the simulations. The probability of levee failure and the extent of the breach caused by compound flood-earthquake scenarios are further determined by Fault Tree Method. The findings provide a practical approach to analyzing levee systems under multi-hazard conditions and enhancing levee resilience.

In-ground slope monitoring is an essential part of landslide early warning systems. Precise movement data from borehole monitors can detect emerging hazards near critical infrastructure. Typically, monitoring is done with inclinometers, but lower-cost alternatives have emerged which have yet to be tested in Tennessee. Time domain reflectometry (TDR) records magnitudes and depths of movements along a buried coaxial cable. When paired with a remote data logger, TDR can wirelessly transmit high resolution movement data in real time, making it promising for landslide early warning systems. Tennessee Department of Transportation (TDOT) has proposed a one-year feasibility study to test TDR for use in unstable soil slopes near highways. The study area is a well-known landslide site along Interstate 40 in Roane County, TN. Careful siting of borehole instrumentation is crucial for accurate monitoring. The goal of this study is to optimize TDR installation, with three specific aims: (i) evaluate landslide morphology, (ii) pinpoint locations and depths with greatest movement, and (iii) assess spatiotemporal patterns across the site. Statistical analysis of prior data from 13 inclinometers showed ongoing slope movement over the 21-acre complex landslide. Spatial interpolation suggested an asymmetrical failure surface with both shallow and deep motion. Space-time cube analysis indicated varying movement rates and timing across the site, suggesting separate landslide bodies. Based on these results, three optimal borehole depths and locations were proposed for TDR instruments. This analysis will ensure accuracy in tests of TDR for early warning system feasibility in Tennessee.